Gas Spring consista...
 

Gas Spring consistancy and limitations  

  RSS

Alan12013
(@alan12013)
Joined: 2 years ago
Posts: 52
2018-02-08 09:23:30  

For tinkering purposes I am wondering what my limitations are on modding a NP2 Trail.  I've considered a new barrel, recrowning the current barrel, trigger replacement or mod, new seals, etc.  I bought some air venturi lube that I will use when I break it down to do my thing to it but I feel that is more helpful with a coil spring gun...  My thinking after seeing the groups with this gun is that the accuracy problem could be caused from inconsistency from the "gas spring" itself?  Does anyone have experience improving a gas spring gun that can offer some tips?  If I recrown the barrel or do any substantial work to the gun I want to know that it should have benefit and not go to waste for a problem I can't fix.  If it could indeed by the "spring" itself, do you think I could order a new one or several until I get one I like?  I ordered a Chrono online a couple days ago that's shipped already.  I know that will help me greatly find out at least the consistency in velocity and to generally help in troubleshooting in a at least a couple areas.  

 

I've saved enough money to basically get any gun I want right now and my logical brain is telling me to get that TX200 that I've wanted for at least the past 15 years or an HW97.  The thought of PCP honestly scares me for some reason but that is an option too and accuracy is extremely important to me.  I like target plinking but I want a reliable hunting gun that I can use on small game and make good headshots with.


Quote
dan_house
(@dan_house)
Joined: 2 years ago
Posts: 78
2018-02-08 13:08:05  

Huge difference in a TX200 and the NP line, both in quality and performance....... 

Gasrams have a short sharp shot cycle (think .22 LR), the spring gun will have a much longer and "softer" cycle.the gas ram perfromance, IMO is far more cosnsitent than any spring; it should act/behave identically most of the time (everything else being equal) Quality of the internal parts (like piston fit on the air tube) will have more effect than the spring or gasram itself.

Groups... how many kinds and wieghts of pellets have you tried in the NP?

Are there marks on the NP's piston? if so then its rubbing on the wall of the air tube. smooth that area out and burnish in some dry lube or moly. You can try buttoning the piston to keep it centered in the air tube. Check to make sure the piston is round. Verify the seal isnt damaged.

My Np has a socket the "big" end of the ram sets in. a wrap or two of electrical centered it and took some of the rattle out. Look for other areas you can change to reduce the rattle from internal parts banging around. Id also try soft bedding the action in the stock. 

Is the stock "hollow" or have spaces under the airtube? adding some weight could help (both under the action and in the butstock)

Doing the other mods you listed arent a waste of time. Mods on these guns are "cumulative", and its the overall improvement that will help its perfromance and behaviour

 

I have no direct expereince with the 97, but on many forums they are hightly regarded. I do have aTX200, and its LIGHTYEARS better than the two gasrams I have. There is a reason its been a winning FT gun for years.

 

HTH

 

dan

 

 

On the Lunatic Fringe of American Airgunning
Proud sponsor of team_subsonic
Charter member of the Western Heretic Alliance


ReplyQuote
Alan12013
(@alan12013)
Joined: 2 years ago
Posts: 52
2018-02-08 22:07:50  

Thanks for the good information!  I am curious about the piston and getting the ram nice and snug.  I've yet to take it apart.  I jumped the gun and started shooting, got at least 200, most 400 pellets through it.  I've shot only a handful of pellets: CP HP, CP Dome, Gamo Hunter (heaviest at like 15.4 grains), Crosman point, and RWS super dome.  I have a ton of JSB, HN, AA, and other pellets en route from an amazon purchase a few days back including a Chronograph, Air Venturi lube, and some other stuff.  I'm going to start record keeping once I take it down and service it.  I'm paying attention to velocity with each pellet, diameter (some are like 5.52 and others 5.53 or thereabouts), weight, and group size per distance interval.  My gun has done 3.5 or worse groups at 10 yards with some pellets.  I have at best achieved 1.8' groups at 20 yards and an average of more then 3.8'.  I am a weekend warrior and only got back into it a month or so ago so I don't get to tinker daily unfortunately until I figure out a way.  I kept all my groupings with my 2240 but tossed most of the NP2's as I figured I was still breaking it in.  I'm really excited to test my pellets with the 2240 because I'm shooting very tight at 10, 20, and 30 yards and before I left the last time I took it out to 50 yards and was on target pretty good but my bulk CO2 started dropping very fast after like 2 shots at that distance.  I suspect when I go out next I will be doing impressive groups at 50 yards.  I haven't tinkered much with the 2240 yet but it does have a steel breech, bulk CO2, and 23' barrel.   Back to NP2...  I'm pretty sure that the stock is hollow... I might use some rock tight and do the soft bedding when I put it back together, will have to research and do my homework on that one though as I've never heard of a soft bedding.  I plan on doing it all at once and doing it best I can.  You've really got me wondering about inconsistency caused by the violent release of that "spring" inside the chamber if it has even a slight wiggle room, if I understand it right then I think that the high quality lube and light mods to tighten it up a bit might actually help out a lot.  Thanks again! I'll update as I make progress.  Maybe even pics if I'm okay with embarrassing myself lol


ReplyQuote
dan_house
(@dan_house)
Joined: 2 years ago
Posts: 78
2018-02-09 11:04:56  

ID start keeping "records" of what you get out of it NOW, so youve got a baseline to measure against afer the mods start.

Id also ONLY make one change at a time, so you know how that one affects it all--remember its a system.

After you tear it down, you'll see places where things cna be shimmed or made to fit better. Mine went from rattling to just a thunk with little effort

On the Lunatic Fringe of American Airgunning
Proud sponsor of team_subsonic
Charter member of the Western Heretic Alliance


ReplyQuote
dan_house
(@dan_house)
Joined: 2 years ago
Posts: 78
2018-02-09 16:21:59  

Soft bedding discussion can be found here

https://www.gatewaytoairguns.org/GTA/index.php?topic=139181.0;topicseen

On the Lunatic Fringe of American Airgunning
Proud sponsor of team_subsonic
Charter member of the Western Heretic Alliance


ReplyQuote
Alan12013
(@alan12013)
Joined: 2 years ago
Posts: 52
2018-02-10 00:03:26  

Halfway through the thread, will pick up tomorrow.  I got one of my shipments in now so I've got my Air Arms heavy dome pellets (2 tins of 250) and my air venture lube (the can looks tiny compared to the pics, but I guess a little goes a very long way).  So I will take it out and at least get a baseline tomorrow with the CPHP, AA FTT, CP Dome, and just to waste the pellets, the Gamo ones too.  Then Sunday I'll clean and lube, then go from there one step at a time.  After reading that thread I attained some good reasons for one mod at a time...  Also I'm tempted to make an account to save 1 guy some time.  I think that soft bedding is a good option to try but not glass bedding.  I saw a video of some one on youtube and it might have even been Tom Gaylord, I feel like it was some one I found to be very credible, they preformed a textbook glass bedding on a springer and got no changes in groupings from before and after testing.  I do think that the soft bedding however could make the gun feel a lot better, help with screw adjustment issues, and potentially help in combination with other things like what you mentioned to help with accuracy.  I tried to bench shoot in many ways last time and one that I tried a lot because the theory worked so well in my mind was securing the but tight on my shoulder and sitting the forearm down right before the trigger guard onto some soft rubber material to allow some vibration while providing a consistent non violent dampening of the vibrations.  Didn't work too well, I didn't find any consistent results attributed to hold at all but it was in the break in stage still.  More to come.


ReplyQuote
NapaSpringer
(@napaspringer)
Joined: 2 years ago
Posts: 16
2018-02-10 11:04:53  

I have both a .22 TX and a .20 97 and if you like/don't mind tinkering I would go with a .20 or .22 97 if you want to hunt with it or .177 if you are using it for target/plinking. I would get the thumbole stock version and then add a Vortek spring kit and then extra parts (trigger, guard, cocking grip )from Rowan Engineering in the UK and you will have one sweet rifle. I can take squirrels out to 70 yrds with my 97.   The TX is a great gun but for field work the 97 is better, easily to load, no anti bear trap latch, and more stock configurations to choose from. 


ReplyQuote
dcw
 dcw
(@dcw)
Joined: 2 years ago
Posts: 61
2018-02-10 12:01:36  

IMO...gas ram or a true "springer" doesn't make much difference...however...I, having both, believe the gas ram (think theoben HW90/Beeman RX) offers an advantage over the springer. it is:

1. adjustable power level

2. re-buildable

3. consistent...(no spring to lose power)

I had an NP Trail. I did a lot of "mods" but it did NOT perform as advertised even AFTER mods and I was never able to obtain any sort of repeatable accuracy.

I have chosen to stay with the proven German and British made air guns for their dependability, accuracy and workmanship. I have two such rifles I purchased circa 1990 and  still shoot them regularly. both have been rebuilt only once.

 


ReplyQuote
mildot 52
(@mildot-52)
Joined: 2 years ago
Posts: 25
2018-02-10 12:06:00  
Posted by: dcw

IMO...gas ram or a true "springer" doesn't make much difference...however...I, having both, believe the gas ram (think theoben HW90/Beeman RX) offers an advantage over the springer. it is:

1. adjustable power level

2. re-buildable

3. consistent...(no spring to lose power)

I had an NP Trail. I did a lot of "mods" but it did NOT perform as advertised even AFTER mods and I was never able to obtain any sort of repeatable accuracy.

I have chosen to stay with the proven German and British made air guns for their dependability, accuracy and workmanship. I have two such rifles I purchased circa 1990 and  still shoot them regularly. both have been rebuilt only once.

 

Sig has come out with a nice gas ram break barrel with a bank vault lock up. I think a guy put the ad for it on the forum. Like to see the results if some one gets one. they are at a good price a lot lower then the rifles you mentioned


ReplyQuote
Alan12013
(@alan12013)
Joined: 2 years ago
Posts: 52
2018-02-10 23:15:24  

I think that the quality of the gas ram itself is important in accuracy.  But as Dan implied, as long as the piston and chambering is solid it can help correct any imperfections from shot to shot.  I guess a better way of phrasing the question I had earlier would be: would an NP2 shooting 1 inch groups at xyz yards shoot even smaller groups at xyz yards if you replaced only the gas spring from a more expensive and well built airgun (assuming you could)?  I do wonder if the "gas springs" are interchangeable?

The 4th all-day of shooting went much better.  Ending the day with a 2.35' 50-yard group and a single shot in a bulls-eye which I didn't have the guts to continue shooting at.  I have a bunch of HN, JSB, etc. pellets coming that I'll also test soon but the AA DFH pellets performed extremely well today.  I'm also excited for the chrono to get here...  I shot some big and some small 5 shot groups...  Average 10 yard was 1.031, and of 2 50 yard groupings (excluding my single shot) I got an average of 2.1538 which is shocking considering that would have qualified as a great 10 yard group the last couple times I took it out.  Average 30 yard was 2.875 inch.   I knew it would go well when the first 2 AA pellets were practically touching at 10 yards.  Strangely though I wonder about repeatability of that accuracy...  I shot more at 20-35 yards with the lowest at 1.75' and the largest at 3.5 with an average of 2.878 at 30 yards.  This tells me my 2 goups and 1 bulls eye were lucky, although they were taken towards the end of day shooting.  I'll give it another 3 outings tops before I call it completely broken in and stop expecting things to change, at which point my notes will be complete and the tinkering can begin.

...I have decided that I'm getting a 97 and not the TX200 (although who knows what the future holds)probably in blue laminate sometime very soon.


ReplyQuote
NCscott
(@ncscott)
Joined: 2 years ago
Posts: 2
2018-02-11 18:02:52  
Posted by: Alan12013

I think that the quality of the gas ram itself is important in accuracy.  But as Dan implied, as long as the piston and chambering is solid it can help correct any imperfections from shot to shot.  I guess a better way of phrasing the question I had earlier would be: would an NP2 shooting 1 inch groups at xyz yards shoot even smaller groups at xyz yards if you replaced only the gas spring from a more expensive and well built airgun (assuming you could)?  I do wonder if the "gas springs" are interchangeable?

The 4th all-day of shooting went much better.  Ending the day with a 2.35' 50-yard group and a single shot in a bulls-eye which I didn't have the guts to continue shooting at.  I have a bunch of HN, JSB, etc. pellets coming that I'll also test soon but the AA DFH pellets performed extremely well today.  I'm also excited for the chrono to get here...  I shot some big and some small 5 shot groups...  Average 10 yard was 1.031, and of 2 50 yard groupings (excluding my single shot) I got an average of 2.1538 which is shocking considering that would have qualified as a great 10 yard group the last couple times I took it out.  Average 30 yard was 2.875 inch.   I knew it would go well when the first 2 AA pellets were practically touching at 10 yards.  Strangely though I wonder about repeatability of that accuracy...  I shot more at 20-35 yards with the lowest at 1.75' and the largest at 3.5 with an average of 2.878 at 30 yards.  This tells me my 2 goups and 1 bulls eye were lucky, although they were taken towards the end of day shooting.  I'll give it another 3 outings tops before I call it completely broken in and stop expecting things to change, at which point my notes will be complete and the tinkering can begin.

...I have decided that I'm getting a 97 and not the TX200 (although who knows what the future holds)probably in blue laminate sometime very soon.

To answer your question in the first paragraph...maybe.  I don't know the differences in the quality of gas rams.  I only shoot springers and do know that well tuned springer can be easier to shoot accurately than an untuned gun.   The key word here being easier.  If you know how to shoot a springer, an untuned gun can be as accurate as a tuned gun.  The tuned gun is just more pleasant to shoot and may not be as hold sensitive.   I believe a good barrel has the biggest impact on accuracy.  HW and Diana make very accurate barrels...at least the ones I've owned.


ReplyQuote
Alan12013
(@alan12013)
Joined: 2 years ago
Posts: 52
2018-02-11 22:54:06  

I've always figured the barrel is the most important part of rifles.  Never understood why some one would spend many hundreds to modify a rifle and think they're improving accuracy yet leave the barrel stock...  Especially for non airguns the first "mod" I'd do is quality barrel, and you can always find better then what the rifle comes with.  Airguns are hard to find barrels, I'm sure they're out there.  It seems most companies take the LW barrel route on their gun like Airforce and some others.   I wish I knew how to work metal.  It's interesting to me that the manufacturers of the HW line make their own barrels in Germany specific for their guns while so many others go with the LW barrels.  It says a lot about the quality and care that goes into their manufacturing.  I might try hunting down a manufacturer that can make me some aftermarket quality barrels for my airguns.  If there was a site selling aftermarket NP2 or 2240 LW barrels I'd buy one tonight.  I suspect a lot of people would.  Although my 2240 is pretty darned accurate as it stands now.  I assume a normal gunsmith can perform a recrown... I will not attempt without a lathe and proper equipment.  When I look down the barrel of my NP2 I can see some short wavy horizontal lines that go across the rifiling that I wonder if could be an imperfection.  The barrel chamber and the crown seem ... unpolished at best, but there isn't any obvious hangups.  Also the twist rate seems pretty fast to me, but most twist rates make absolutely no logical sense to me...


ReplyQuote
dan_house
(@dan_house)
Joined: 2 years ago
Posts: 78
2018-02-13 11:48:16  

gas rams should be interchangable IF the bases are the same size ( or close enough you can shim it). Barrels? maybe doing some kind of lapping would help. If your seeing lines ACROSS the rifling, then at least polish the bore a bit to reduce those.

and depending on how much you want to geek out, you can add or remove piston wieght, add some length to the piston (makes the stroke shorter, reduces the mount of raw power it makes), open or reduce the TP.....

But--and remember I am a big Crosman fan--these are inexpensive guns built to meet a price point. While they can be made nicer, chasing "EuroMatch" performance will drive you nuts.... ?  

 

On the Lunatic Fringe of American Airgunning
Proud sponsor of team_subsonic
Charter member of the Western Heretic Alliance


ReplyQuote
Alan12013
(@alan12013)
Joined: 2 years ago
Posts: 52
2018-02-13 15:37:26  

Okay, thanks again for the info.  I totally agree with you on crosman btw, just hoping to learn something through tinkering. Plus it probably helps me appreciate various products and manufacturers a bit more.  I took the NP2 out last night with some new pellets (first time I've ever used pellets outside of crosman except the AA pellets I shot last week) and the JSB Straton Jumbo's did amazing.  I actually had my NP2 putting pellets into the exact same hole on several occasions.  If I can get repeat performance with those pellets it might delay the tinkering or at least change the methodology of it.  Downside is only AoA sells the .22 JSB Straton from what I can tell, so I hope they have plenty in stock...  Overall I had tight groups with that pellet and the Jumbo Monsters came in a pretty close second, which is awesome considering I think they would also be good small game pellets.  I'm going to do a bit more research but I'm wondering if the pointed straton pellets did so well because of the diameter being 5.50 while the rest were 5.52 or thereabouts.  I didn't have the AA pellets with me but the NP2 did well with those last week at 10 yards and I think that they might be 5.50 also.  I cant wait to see how the 2240 does with the JSB pellets, even if I only improve a little, I'll be chasing sub 1 inch at 50 yards on low-count groups.  Good timing too ... I have a "competition" this weekend... my Mother and Step Dad think they can outshoot me with their 10/22s at 50 yards...


ReplyQuote
ekmeister
(@ekmeister)
Member of Trade
Joined: 2 years ago
Posts: 459
2018-02-13 17:17:42  
Posted by: NCscott

 

To answer your question in the first paragraph...maybe.  I don't know the differences in the quality of gas rams.  I only shoot springers and do know that well tuned springer can be easier to shoot accurately than an untuned gun.   The key word here being easier.  If you know how to shoot a springer, an untuned gun can be as accurate as a tuned gun.  The tuned gun is just more pleasant to shoot and may not be as hold sensitive.   I believe a good barrel has the biggest impact on accuracy.  HW and Diana make very accurate barrels...at least the ones I've owned.

I'm with you on about 90% of that, just, respectfully, not the part where an un-tuned spring gun can be just as accurate as one that's been (properly) tuned. 

When it comes to tuning a springer for top performance and accuracy, installing the right parts to de-torque the shot cycle, and making sure the muzzle crown is basically perfect, can make all the difference between one that's tuned and one that's un-tuned.  Installing an upgraded mainspring is also very useful when it comes to those makes and models that suffer from early spring breakage and early power loss/ spring fatigue, although that last item is not admittedly about accuracy per se. 

The shot cycle of an air gun with a metal coilspring can be just as linear as one with a gas ram if the tune is done correctly.   As to perfect muzzle crowns, of course even the venerable PCP needs a good crown and it will suffer from accuracy problems if it doesn't have one.  I just think that people tend to blame a lack of accuracy from a springer on the fact that, well, it IS a springer.  They'd probably be much quicker about checking the muzzle crown of their PCP rifle if the accuracy wasn't there.  From what I've seen here over the years, I guarantee you than some of the best deals on the air gun classifieds are air rifles that 'just aren't accurate', when all they need is some attention given to the muzzle crown.

BTW, when I talk about de-torquing the shot cycle, I don't want to contribute to the rumor mill having to do with those notorious needle bearings.  Eeek!  It can and should be done another way.  Those needle bearings should never be brought within a mile of a spring gun and its repetitive-piston-dependent shot cycle.  You know--I mean these things:

Koyo NTA-1018 Needle Roller and Cage Thrust Assembly, Open, Steel Cage, Inch, 5/8" ID, 1-1/8" OD, 5/64" Width, 15000rpm Maximum Rotational Speed, 6830lbf Static Load Capacity, 2200lbf Dynamic Load Capacity

Back to the crown subject, probably something like 15-20% of the many air rifles I've tuned over the years needed muzzle crown work when I got them in here.  Don't misunderstand what I mean by that--although some of the crowns were damaged by something or someone after they leave the factory, many other crowns came--and still come--out of the factories with less than a perfect crown from day one.  When I get one like that, I take care of it.  If I didn't, it would make my tuning work look bad.  Saying it another way, everything else about any shooting arm can be perfect and consistent, whether it be spring-piston or PCP air rifle, or even a firearm, but if the muzzle crown is bad the accuracy will also be bad.  It doesn't take very long to fix a muzzle crown if you know how to do it.  If you're having any accuracy problems with one of more of your air guns, it's at least worth taking a look at the crown.

Safe and Happy Shooting!

Ed, the Airgun TuneMeister

https://www.airguntunemeister.com/


ReplyQuote
ekmeister
(@ekmeister)
Member of Trade
Joined: 2 years ago
Posts: 459
2018-02-16 21:16:29  

I think you were referring to this one?  I'm the one who posted the link.  Now you have it here, too.

SIG SAUER Introduces the New ASP20 Break Barrel Air Rifle

Safe and Happy Shooting!

Ed, the Airgun TuneMeister

https://www.airguntunemeister.com/


ReplyQuote
classicalgas
(@classicalgas)
Joined: 2 years ago
Posts: 70
2018-02-18 13:58:34  

So long as you realize that in  working with the NP2 you are handicapped, tinker away, you'll learn a lot.

In my view, unless you shoot a lot of strings over the chrono, with sized and weighed pellets, you don't know whether your accuracy issues are due to velocity,  or something else.

Gas springs offer no advantage  over steel spring if you are tuning (you can eliminate steel spring buzz, the only advantage gas springs have is lack of buzz) and  they have several disadvantages. Cocking force is higher for the same power, they offer less tune options, and they will leak down at some point.

Until you've pushed a few pellets down the bore, you haven't a clue whether your bore is your accuracy limitation. EVERY low end break barrel  springer I've pushed a  few pellets through had tight spots in bad places, and was rough  to some extent.(The CZ's may be an exception to this rule) Lapping (fire lapped or cast in bore  lap, not polishing with a soft mop) will almost always help a cheap gun.

People tend to ignore the importance of balance and power to weigh ratio when tuning springers for accuracy. Low center of gravity, weight distributed towards the ends,  and a power to weight ratio of no more than 1.5 to 1 (12 ft/lbs in an 8lb gun, 18 ft/lbs from a 12 lb gun) will do more for repeatable, consistent accuracy than anything else, given  reasonable velocity control and a  fair to good barrel (with consistent pellets that fit) Absolute accuracy  vs what you can do on a consistent basis under field conditions are two very different things. A forgiving gun, not hold sensitive, will do more to reduce your average group size than anything else. A steel muzzle brake and  a half pound of lead in the butt is a good place to start.

I'm a fan of hard bedding springers, I've always seen an accuracy improvement with that method(fewer fliers, smaller average group) Some superglue(not gel) soaked into the wood under the  action  screws, steel flat washers replacing the star washers, a  couple pads of epoxy putty in relieved areas  in the inletting ,and socket head machine screws coated with low strength locktiite complete the package.

Real world accuracy is the result of controlling a complex array of factors, several of them not at all obvious.


ReplyQuote
Alan12013
(@alan12013)
Joined: 2 years ago
Posts: 52
2018-02-21 15:33:52  

Thank you.  The weighting idea makes complete sense to me.  I will keep that in mind as I proceed.  I've noticed when I hold the rifle as if the back was heavier it's shot tighter groups.  Basically I apply downward and back pressure on the pistol grip with my trigger hand as I shoot (yes it's hard to consistently remember to do this) and it has made a difference.  I've spent almost an hour trying to learn about this lapping business this morning and found lots about the theory but not much about it's practice.  From what I can tell, I would properly push a pellet down the barrel to examine for imperfections, then I would buy some type of JB compound and maybe a cleaning pellet and coat them in the compound before firing?  ...and do that 5-15 times before dry cleaning really well.  I'm really excited to do that to my 23' crosman barrel on the 2240.  I tend to agree with you on gas ram not offering much more in forms of tuning...  I do love springers but am more interested in a 12fpe gun that shoots accurate and smooth and tuning to achieve that oppose to "more power" type of mindset.


ReplyQuote
James Perotti
(@jpsaxnc)
Joined: 2 years ago
Posts: 75
2018-02-21 15:52:53  

Have you pushed any pellets through the barrel by hand, to check for tight and loose spots?


ReplyQuote
classicalgas
(@classicalgas)
Joined: 2 years ago
Posts: 70
2018-02-21 23:04:57  

Here's the old firelapping airguns tutorial I did years ago...please excuse typo's and punctuation, it needs editing...

Fire lapping tutorial

by Scot Laughlin

 

The following is intended to be the first of two segments on lapping your airgun bore. This one is on “fire lapping,” a somewhat controversial technique borrowed from firearms accurizing. One detractor called it” firing sandpaper down your barrel”. Sorta scary, considering how often we read that you need to treat your airgun barrel very carefully.

 

Lapping can be described as using a soft metal lap, loaded with an abrasive paste or slurry, to smooth and flatten a metal surface.(sometimes two parts are rubbed together to abrade both to a better fit)

 

How do you decide that lapping is worthwhile and which technique is best to use, hand lap or fire lap? For me, the process looks like this: Is the gun I’m considering lapping less accurate than I think it should be and have I dealt with the usual suspects, such as loose screws, bedding, crown, scope mounts, etc? If I push a pellet down the bore, do I find the muzzle loose compared to some other part of the bore, or a series of tight spots? If yes to all the above, I plan to lap.

 

Fire lap or hand lap, which one? When I want to get the very most out of a gun, I hand lap. I have to be pretty committed to that goal to hand lap a .177 bore as they are much harder to do than larger bores and pretty much a PITA.

 

Fire lapping is almost too easy, but less controllable, and with less feedback built in , so it’s easier to go wrong, and gives a less than perfect bore. I tend to fire lap cheap guns and hand lap more expensive guns, but it depends some on the other criteria as well.

 

I’d suggest doing a Google search on” fire lapping” and choose accordingly, but my take is this: An accurate bore is consistent in diameter, or at least, no part of the bore is smaller than the muzzle and smooth as possible, with rifling that keys into the pellet well enough to spin it, but not so much as to prevent a good seal at the skirt, or distort the pellet. Smoothness to reduce leading and improve consistency, and tightest at the muzzle to insure, as much as possible, that the pellet does not tip leaving the bore. Crown and muzzle damage are proven accuracy destroyers, (see previous) so caution with cleaning rods makes sense. On the other hand, if you’ve ever tried to remove .001" from the edge of a piece of sheet steel using 400 grit sandpaper, you know how slow that is.

 

I found it interesting that most shooters who’d fire lapped were happy with the results (unless they “washed out” the barrel throat,) bullet makers don’t have a problem with it or like it a lot, but barrel makers that already hand lap their bores are against it.

 

Fire lapping if done right, smoothes the bore, tends to cut high spots while leaving low, thus “truing” the bore, making its ID more consistent. The breech end will be cut more than the muzzle (the compound wears as it is carried down the bore by the pellet) so the breech ends up slightly bigger. This could reduce velocities in Springer’s by reducing friction and allowing an earlier release of the pellet as pressure rises. In my experience the loss is small (10-20fps) to nil. The upside is a very slight choke effect, and improved accuracy. It would seem wise to do no more cutting of your bore than needed, let’s say 50 shots max (based on the firearms stuff that I’ve read). You should have some recent test groups to make comparisons.

 

I’ve had good luck with this technique on several airguns of American and Chinese makes and one Brit PCP. No gun that I have fire lapped shot poorer groups after lapping than before, and some didn’t show any improvement. I’ve never done a match or high end PCP guns....your mileage may vary and this is for informational purposes only.

 

 

 

 

You will need: about 50 ringed pellets (silver jets or similar) in the caliber you want to lap

 

2 lapping plates, hard flat surfaces to roll your pellets between

(Since a lap cuts by holding sharp, hard particles against the work piece (bore), you need to load the pellet with abrasive.)

 

Lapping compound: DO NOT USE VALVE GRINDING COMPOUND. It’s far too coarse), or even fine clover compound, (the grit size is inconsistent so you won’t get a good finish). You can try toothpaste, JB bore paste, or rubbing compound, but I go to the expert. Lead Bullet Technology has been making custom molds for lead bullet shooters for near 20 years, is a big believer in lapping, and sells a bore lapping compound I’ve used many times. Good directions are included.

 

Some q-tips for cleaning crevices, your cleaning rod or pull thru, whatever bore solvent you trust with your airgun

 

Really clean the bore well. Your objective is to cut steel, not clean out old lead deposits. Next put a dry pellet in the bore, and push it through, feeling for tight spots. Do this a few times and mark the tight spots on the outside of the barrel.

 

Take ten pellets, smear some compound on the lower plate, roll the pellets through it until they’re covered and grooves are full. You want to use a little pressure, but not enough to distort the skirts. Wipe off the pellets lightly, you don’t want gobs clinging, but not dry either (also your fingers). Load your gun with a treated pellet and wipe off any excess compound in the seal area, and fire.

 

Note for spring guns: If you find it difficult to load a pellet into the breach, load normally for the first few shots. Then seat the remainder of the pellets about 1 pellet length into the bore. This is to prevent too easy a fit and potential loss of velocity. If you have an easy load breach, load all lapping pellets deep. Repeat until all ten are gone.

 

Thoroughly clean the bore again and do a pellet push through test. Look at the rifling marks on the pellet. If the tight spots were not very noticeable, and you feel cautious, shoot some groups. Be aware that you may have to fire several fouling shots to get representative groups. Then, if you still feel spots tighter than the muzzle, treat another 10 and repeat the process. You should do some test groups between each lapping groups of ten pellets even if you still find tight spots.

 

So how do you know when to stop? Ask yourself…Is the gun more accurate than before? Is it more accurate than after the first series? Are rifling marks in your pushed pellets sharp? Do you still feel distinct tight spots other than the muzzle?

 

I usually shoot between 30 and 50 lapping pellets in groups of ten, then clean and load another 10 with a polishing bore cleaner like JB or Gold Medallion and fire those. If I have easy access to the breach I’ll soak a patch in gold medal and give the bore a couple dozen strokes. Also, because it will never be cleaner, now is the time to treat your bore with an anti friction coating of your choice such as Militec, moly, that new Teflon lube, or your favorite pellet lube if you use one.

 

Next time I’ll talk about hand lapping...if you think fire lapping was tedious, just wait!

 

 


woodnbow thanked
ReplyQuote
classicalgas
(@classicalgas)
Joined: 2 years ago
Posts: 70
2018-02-21 23:17:36  

And here's the cast lap tutorial....looks like the pictures didn't copy here. If there' interest, I can probably find them

 

Hand Lapping Your Airgun Bore Tutorial

By Scot Laughlin

 

Hand lapping offers some advantages over fire lapping. Since a well cast lap fills the bore, the chance of rounding or reducing the depth of the rifling is greatly reduced. A lap can only increase the bore diameter to the size of the largest section, (since you can only bump up the lap to that (largest) diameter) so worries about creating an oversize bore are greatly reduced. You can feel your progress, tight spots can be worked out, and a slight choke can be created at the muzzle. In general, it’s a more finely controlled process than fire lapping. As always...this is for informational purposes only, YMMV, don’t blame me if you mess up.

To effectively hand lap an airgun bore, you need a cast lap that exactly duplicates the bore of your gun, a rigid rod that you can cast a lap on, and a ball bearing handle for the rod. This will allow easy rotation with the rifling under the loads created as you stroke the loaded lap down the bore. You will need easy access to the breach of the barrel. DO NOT lap from the muzzle, too much chance of damage to that critical portion of the bore. Also lapping compound, (we’ve talked about that in the previous segment) a “bump up” rod. (a length of uncoated brazing rod that fits your bore as close as you can manage), and something to tap the bump up rod with such as a tack hammer or short length of metal bar. Also you will need a little bit of lead, old pellets will do, and a way to melt and pour them accurately.

I’d recommend doing at least a couple practice barrels before you attack your favorite gun. Find a beater .22 rimfire at a gun show or perhaps buy a .22 and a .177 barrel from Crosman, pick up a Cummins Chinese gun or whatever. I suggest doing a .22 first, because for practice purposes its lots easier to get a good cast in the bigger bore than in .177.

Push a few pellets thru the bore, feeling for tight spots, and mark those spots. If the last inch of muzzle is much looser than most other spots, there’s relay not much you can do. A lap has to be cast near the muzzle, and will jam before you get very far. Cutting off the loose spot is about your only option. You can try to fire lap, but you’ll have to remove so much from the rest of the bore that you run the risk of damage.

Some way to securely hold the barrel is very important as you are going to push and pull pretty hard on it. One good way is to take a couple 8” lengths of 1x2, clamp them together with a piece of manila folder between them. Now drill a hole the size of your barrel, or a slightly smaller down the joint. Cross drill for wallboard screws in about 6 spots, and unclamp. Pull out the paper, dust the grooves with rosin (weight lifters rosin bag) and screw one block at about hip high to a solid workbench or doorframe, groove level. Put the barrel in the groove, screw down the other block.

For the handle, you can try a store bought swivel, or “ball bearing” cleaning rods, but I find they don’t rotate easily and often fail. I use bike quick release hubs (any bike shop will have a few laying around and they’ll sell them to you cheap) from which I’ve cut away the flanges and then ground smooth. I rebuild the bearings, set them up just a bit loose and lube with a light grease or heavy oil. I assemble them with the hub near one end of the axle to leave a longer stub at one end. I thread on a standard nut (sometimes called a “city nut” or “anti-theft nut”, LocTite it, then drill and tap it for the setscrew used to grab the lapping rod.

 

 

 

The rod needs to be rigid and straight, and stay that way. The best solution I’ve found is piano wire in larger sizes, far more rigid than most cleaning rods.

To prep the rod to receive the lap, you need to grind or turn it down to about ½ bore diameter and groove it to help it retain the lap. Reduce and groove about 1” of rod (or a long set screw if using CF rod)

Your ladle can be a rough spoon hammered out of some sheet steel, an old serving spoon with a notch filed in one edge, something that will hold about 10 pellets worth of lead. You’ll need a propane torch to melt the lead, a dab of beeswax or soldering flux (rosin type) to clean the lead. It would be best to melt and pour outdoors, but at least get good air circulation, and move anything burnable away.

Disassemble the gun enough to allow easy access to the breach. With barrel cockers, remove the barrel from the gun, with side and under levers, pump and co2 guns, you’ll have to work through the receiver. (Make sure your rod is long enough) Cut your bump up rod to just a couple inches longer than your bore, and square the end. If you are doing a Benji or similar, cut a few lengths of plastic straw and split them down one side, these will protect your receiver. Clamp the barrel at about 80deg; you want to pour the molten lead at a bit of an angle. Wrap the rod with several turns of Teflon pipe tape or glide dental floss, about an inch below the reduced and grooved section at the tip. Get an easy slip fit in the bore, just tight enough to hold the rod where you put it (no handle yet).

 

 

 

 

 

To cast in a .177 bore you will probably have to heat the muzzle some. I find a crayon mark melts at about the right temp. In .22 you probably can cast in a cold or just warm bore. Once the barrel is warm/hot, with the tip of the rod just showing, melt the lead (while keeping the muzzle warm, a helper is nice) When lead is ready, pull the rod down about ½”-1” and pour. (careful of your feet and anything else on the floor or bench top) Fill the bore to the muzzle. Give the lead a minute or so to set, and tap the other end of your rod to bring the lap about ½” out the muzzle. You should see a perfect cast of the bore, rifling sharp and clean. If not try again.

When you get a good cast, trim the end square just below the flare left by the crown, and file a couple shallow grooves around the lap with a triangle file. Put a couple drops of oil on the lap, and attach your handle. CAREFULLY pull the rod back until you see the Teflon on the rod. (You should see the rod rotate as you do so). Arrange some sort of back stop or lanyard to help keep you from pulling the lap fully out of the bore. If the lap ever leaves the bore completely, you need to cast a new one. Run the lap back out the muzzle ‘till the grooves show, and rub a dab of lapping compound into the grooves. Pull it back into the bore about 1”, then reset your handle against the breach or receiver end as a forward stop. A faucet washer slipped on the rod makes a good bumper. (by not working in the last inch of bore, you end up with a slight choke)

Now the work starts...As you run the lap back and forth thru the bore, you feel areas of resistance, probably in the areas you noticed with your pushed pellets. Concentrate on these spots until they loosen up. When the lap runs pretty easily, find a loose spot, slide your bump up rod down the bore to touch the end of the lap, and tap the end of the bump rod once. The lap should feel tight in the bore again. Repeat this process, adding a drop of oil at the muzzle on occasion, until the rod feels the same in all parts of the bore. Early in this process at times when the lap has loosened and just before bumping up, let it run out to the muzzle, and out to the throat of the breech. Don’t let the lap come out of the bore, ever. Don’t let the rod rub in the bore or receiver; wipe off any compound you see on the rod. NOTE: If you haven’t got a bore that feels good by about 100 strokes, it’s a good idea to cast a new lap. The old one will be worn, and you risk rounding the edges of the lands.

When you have a bore that feels even, (or you just run out of patience) stop. Remember, you don’t have to get it perfect this time, you can repeat the process at another time. Clean the bore, breach, etc carefully; you don’t want lapping compound in the guts of your gun. Reassemble the gun, and test. I’d recommend using lubed pellets from the first, or treating the bore, it’s as clean as it’s ever going to be.

I’ve found that lapped bores tend to be less pellet fussy (if not oversize to start with) more accurate, and need less cleaning. Try a few and let me know how it works for you...

Scot Laughlin

 

 


ReplyQuote
RedFeather
(@redfeather)
Joined: 2 years ago
Posts: 72
2018-02-22 13:11:03  

Sounds like you are getting things sorted out but I'm surprised that there was no discussion of one of the major buggaboos in springer inaccuracy, namely, scopes. You can have the finest gun in the world but, if the scope breaks, you might as well be throwing pellets. I'm guessing you have a decent scope, since you are getting better groups. But you might want to revisit your mounts to be sure they don't creep and the forend screws for tightness. You may already have done all this but thought I'd just toss it into the mix of variables, which are legion. Have fun!


ReplyQuote
Alan12013
(@alan12013)
Joined: 2 years ago
Posts: 52
2018-02-22 23:30:08  

I don't think I could have gotten any better information.  I now have some serious homework.  I figure I will start with lapping the barrel, I am undecided which method to use until I can push some pellets through and see what it feels like and looks like.  I checked LBT's website and couldn't find their lapping compound on there so perhaps I can order it elsewhere or they sell it at Coastal here in town (they have a ton of barrel lubes, paste, polishing compound, etc...  I like the idea of the quick release bike thing as a starting point in making a well turning rod, I have been haunted trying to think of a solution for pushing pellets down the barrel that will rotate smooth as possible with the rifiling, even made several trips to goodwill (did make my own spring compressor though).  I never even thought about casting my own rounds btw... that will be a rabbit hole for another time though.  I will certainly always look to the power to weight ratio when working on this gun and whatever others I decide to mess with, that was good info to look for.  I know that a barrel crown is really important and common sense tells me that it's crucial but I just don't have the tools for that so as a last resort if I am dead set on willing this gun to shoot I am not above taking a budget springer to a barrel worker if doable.  I will spend some more time thinking and researching ways to smooth out the firing cycle, now that I've taken it apart to clean and apply air venture lube, I know what it looks like and can let the brain storming begin (no needle bearings lol).  Trigger will obviously need addressed but right now I've shot it enough times with good form and follow through that I don't think the trigger is one of the main fundamental accuracy problems I'm having (although it will be addressed since tuning can be about the "culmination of a lot of small things"). 

and for the last point...  I'm pretty sure it's not the scope, I've mildly trouble shot the situation and think that it's something else. 

Plus its not that bad, reasonable groupings I think for a power-over-accuracy mass-produced gun that may as well have been designed by the marketing department lol  I do like shooting it but 1 inch groups at 10 yards with most pellets and 2 different scopes, seems like primarily a barrel issue to me.  I know I'm not going to be able to recreate an R9 breakbarrel with this gun but I can hope to decrease pellet fussiness and get sub half inch groups at 10 yards and sub 1 inch at 25...  Thank you all again, that was awesome info.


ReplyQuote
classicalgas
(@classicalgas)
Joined: 2 years ago
Posts: 70
2018-02-23 19:06:19  

Keep in touch, tell us what you find, and how it works out.

If you add some weight and tune the gun down a bit, five shot single hole groups  at 33 feet/10 meters aren't an unreasonable goal. I had a couple  (much cheaper  than the NP2)Chinese sidelever guns achieve that level of accuracy.


ReplyQuote

Please Login or Register