I decided to do some experimenting with different tunes for my FWB 124. I bought the gun broken and it had a tune kit of some sort in it but the seal was trash, had a hole in it.
The gun also came with a new JM Pro Mac kit and I also just got in a Twister spring from JM to try. When I first rebuilt this gun I also deburred everything and installed delrin buttons on the rear skirt of the piston.
I used moly paste on the guides and a very light amount of tar. There is no twang with any of these kits As you can see in the pic there is quite a bit of difference in these spring kits.
On top is the original spring and spacer. The spring is 8.25” long with 27 coils of .125 wire and a 1.360” spacer. Oal of around 9.610.
With a tight seal it was very smooth shooting and pushing the JSB 8.4 at 750 fps for 10.5 fpe. I think this spring is slightly collapsed as it is 3/4" shorter than the Pro Mac spring but only has one less coil.
Next I installed the Pro Mac kit and it was shooting the 8.4 at 780 fps for 11.4 fps.
Spring is 9" long with 28 coils of .125 wire. It has a white plastic spacer about .900 long that goes in the piston and a metal one .200 long that goes on the rear spring guide. The gun was slightly harder to cock and is a little louder plus a little harsher. But not bad and I could live with it like this.
Next I decided to try the Twister spring. I followed JM's recommendation and lightly deburred the inside and end of the spring. Also tapered the outer edge of the rear spring guide. This spring twists on the rear guide very tightly and there are no spacers or top hats used. The spring measures 11.375 long and has 36 coils of .125 wire.
On this install I noticed how tight my seal was so I removed it and sanded a few thousands off in my lathe. It slides in much easier but is still fairly snug. This also could have and probably did help with the power increase. This spring jumped the power up to almost 13fpe with the 7.33 going 925 and the 8.4 going 835 fps. It is a little harder to cock but the shot cycle and noise are about like the Pro Mac kit.
I need to shoot it some more and put a couple hundred rounds thru it to see if I like it or if I’m going to put the JM kit back in.
I'm just a tinkerer and hopefully there is some info in here that someone can use to help them make a decision.
Thanks for reading.
You put together a very-nice review. Thanks for the good work, including some of the smaller details.
Some years back I used a different model 124/127 spring that JM used to sell. It also utilized no spacers of any kind, just like the Twister. I like the simplicity of that approach, although I know it may require you to deal with more spring pre-load. IIRC the ID of that older spring may have been just a TINY bit larger--i.e. not as hard to get on the guide--but still no twang.
It's been something like 4-5 years since I used that other spring the last time, and I can't remember what he called it. It definitely wasn't called a 'Twister'. I think it's very-interesting that with the right spring, the FWB 124 produces very-similar velocity and FPE as an R9 with a factory spring. It's a nice upgrade.
I imagine I'll be seeing another 124 here before too long now that I'm working on springers again. From what I saw before, there are A BUNCH of them still out there--most of them begging for at least a new piston seal and a simple application of better lubes if nothing else. (For some reason I never saw a single .22 caliber .127).
I've been waiting for someone to tell us what that Twister spring could do, let alone the other JM options, so once again thanks for the excellent review, including the photos!
Nice job Randy! Now you got me wondering how the Pro Mac kit would fair having turned down the piston seal. Your results with the Pro Mac kit is very similar to my results using this kit. I also have a twister spring awaiting install and interested in seeing what my results will be in comparison.
JM also suggests using a spacer on the rear guide with the twister spring to help prevent galling. I wonder if one would see an addition increase in velocity, though from your results it wouldn't be needed. Again I say nice job Randy.
Ps. How deep do you bore for the buttons?
Thanks for the compliments guys. I'm going to shoot this Twister spring for a while and see how I like it.
I think the ProMac kit would have been 20-30 fps more with the seal sanded down but that is only a guess. I may find out down the road if I decide to reinstall it.
As far as the holes go I went half the thickness of the skirt but don't recall what that measurement was.
Looks like I will be putting the ProMac kit back in. The Twister gives more power but at the expense of a harsher shot cycle that I don't like. It wasn't as noticeable until I shot it on target outside. It was still very accurate but the gun really jumped and it was louder and harsher. I just didn't think it was that bad when I chronied it but I wasn't shouldering it at that time.
So I feel the best compromise of power and smoothness is by using the ProMac kit. At least it is in my gun. Others may feel different and want to go for more power and the Twister will give it to you. I like smooth too.
Looks like I will be putting the ProMac kit back in. The Twister gives more power but at the expense of a harsher shot cycle that I don't like.
Sometimes you can soften or break in a mainspring with that kind of shot cycle by leaving the rifle cocked for a while. In the case of an R1 kit that ARH/ JM used to sell, he actually told me to leave it cocked overnight. That wire was pretty thick though. You might try leaving the .125" Twister spring cocked for 2 hours then shoot 5 pellets and see what it's like. If that's not good enough maybe another 2 hours and see what it shoots like. Then maybe another 2 hours, etc. You can check it on the chronograph when you're doing that test shooting to see that your velocity hasn't dropped much if any but it shouldn't. It may take 10-15 shots for it to level out. This may sound like heresy but it really isn't. I've done it before and not hurt anything. If you're thinking about scrapping the spring anyway you're not going to hurt anything that really matters. It's just a thought.
Hi Ed
thanks for that info. I figured there is something that can be done with that spring setup to lessen the harshness but if it lowers the power then the Promac kit would be a better option. I'll take your advice over the next several days and see what happens.
Hi Ed
thanks for that info. I figured there is something that can be done with that spring setup to lessen the harshness but if it lowers the power then the Promac kit would be a better option. I'll take your advice over the next several days and see what happens.
You're welcome. I can add a little more. I was in a rush to get to the store when I wrote my first reply.
The R1 kit I'm referring to had thicker, .150" wire (it might have been .148" wire, but that's really no difference). It was also wound to a pretty-small diameter. Those factors tend to result in harsher behavior at first when it comes to spring-piston air gun springs. The kit I'm referring to got great velocity, but also had that harsher-than-ideal firing behavior when you first installed it. Leaving it cocked overnight made a very-noticeable difference in softening the shot cycle (although it was still quite a powerhouse, it was no R7! ).
You're not going to hurt a spring gun mainspring by leaving it cocked in 2-hour increments. You're just hurrying-up the break-in process that normal shooting sessions would provide in one year's time or so.
Just so you'll no this isn't theory, I've used the method on many springs in the past. I must admit, I approached the whole 'leave-it-cocked' thing gingerly on kits other than the one I mentioned above with the thick spring wire. So, I'd usually try doing it for one hour and see if there was any difference in smoothness. If that wasn't better I'd leave it cocked for another hour and check again, etc. I never lost any appreciable velocity loss by doing so, but I could tell at least some difference in smoothness at some point.
As to the subject of velocity, keep in mind that after an instance of leaving the rifle cocked, your first few shots over a chronograph are going to be slower than they were before you started. There's a quick fix for that, though. Don't just shoot one pellet and expect to see where the velocity comes out in the way of a final number. Instead, shoot 20 pellets or and see what you have then. At that point, any difference you get compared to where you started should be very-small, if any.
You know, there's an old post around here somewhere about testing the effects of leaving a springer cocked as to velocity loss, even for one week or more at a time. The test was done years ago. The man doing the test did use the method where you shoot 20 or 30 shots before you tested again. But, anyway, IIRC the loss at 1 week was only 10% or so, the loss at 2 weeks like 15%, you get the picture. I think it went all the way out to at least 6 weeks of leaving the rifle cocked. The rifle would have still been usable, although I'm sure you'd have to do some adjustment of your scope elevation turret to account for the decrease in velocity and the associated drop in POI.
It's funny, but this very subject came up the day before yesterday concerning one of my own springers, a .22 caliber RWS 34 Panther with a Maccari .128" wire mainspring. I hadn't shot it for awhile, and wanted to do a little indoor testing, so I took it out of its case. I can't remember why I did it, but I cocked it and left the barrel in the open position (safety on), with the rifle laying on my couch. It remained that way for 15 or 20 minutes IIRC. (Edit: It might have been as long as an hour, because I really wasn't watching the clock. Something else distracted me. But, I don't think it was any more than 1 hour).
When I returned to shoot my first H&N FTT pellet over the chrony, I got a reading of 705 fps. I thought, "wait a minute, i know this gun shoots faster than that". So I immediately shot two more pellets, and both of them were right back at 740 fps, just like I remembered. It had recovered that fast.
I don't do the spring softening process on every rifle I tune. I only do it on the ones that strike me as being less than ideal when it comes to having a shot cycle smooth-enough to provide a good target hold-on when looking through a scope. That pays you back in better accuracy. (And, of course, the same thing applies to the use of open sights, if not more-so. The ballast provided by the weight of a scope tends to calm-down the springer shot cycle).
Wow, thanks again for all this info. You are a wealth of knowledge and I appreciate it very much as I'm sure others do that read your posts.
I've been tuning my own guns for about ten years plus some for friends including lots of pcp's. I love taking something broken like this gun and bringing it back to life. I've also learned a lot from other peoples posts like yours and then doing things myself. Sometimes it works out and sometimes it don't.
Thanks again for all you do.
Hi Ed
thanks for that info. I figured there is something that can be done with that spring setup to lessen the harshness but if it lowers the power then the Promac kit would be a better option. I'll take your advice over the next several days and see what happens.
Hey randy,
I guess if you're going to keep us updated about the POSSIBLE 'softening' of the ARH Twister spring (by leaving it cocked). If so, hopefully you can do it soon if anyone else here might benefit. I just checked the ARH site and it says the springs are being "closed out".
Now, I don't want to raise a false alarm here. Sometimes his "closeout" items remain on his site a little while before they're actually gone. On the other hand, the meaning of the word is pretty-clear, so we can't complain if we try to buy one and find that it's simply too late.
I'm not needing or wanting one myself right now or I'd buy it. But, others may be waiting to hear how it all turns out. And, actually, I am too. It's not like you 'owe' it to any of us, it's just that it may prove to be some very-helpful information. I'll be watching this thread. Thanks.
http://www.airrifleheadquarters.com/catalog/item/251483/10335554.htm
Hey you're the Jeep avatar guy right?
Some "way wipers" will extend the ways' lifespan of that lathe, chunks of felt are almost free compared to new ways.
Not "might" but WILL, keep you from running chips under the carriage, and act as a oil reservoir.
This style might work for you, L shaped plate and some felt, I see no need for the trim bit.
Gratewhitehuntr, thanks for the tip about my lathe. I'll look into something like that.
Ed,
I had some time today and I tried the leaving it cocked for an hour then shooting a few. Can't say there was much difference but I only did it twice. However my curiosity got the best of me and I wanted to see what the PM kit would do since I sanded down the seal. It wasn't really a fair comparison before since I sanded the seal down after taking the PM kit out . Well guess what!
With the PM kit back in it and the seal sanded down it is shooting the 8.4 JSB at the exact same velocity as the Twister spring. And with a much nicer shot cycle. I hit 845 fps with the PM kit and 8.4 JSB. I hit 842 fps max with the Twister spring and same pellet. So it looks like my tight seal was holding the fps back quite a bit as it went from 780 to 845. I shot about 25 shots over the chrony just to double check and they were all from 835 to 845 and the variance was probably me not placing the gun exact every time.
I'm a happy happy man.?
My advice, which isn't worth much, would be to put the promac kit in and be done with it. If you're on a tight budget then the Twister spring would be a good option for a lot less money, but a harsher shot cycle. There may be other tuning things to do with the Twister to help with the shot cycle but since it is so long and fits tight there isn't a lot of room to play with.
My opinion only.
Gratewhitehuntr, thanks for the tip about my lathe. I'll look into something like that.
Ed,
I had some time today and I tried the leaving it cocked for an hour then shooting a few. Can't say there was much difference but I only did it twice. However my curiosity got the best of me and I wanted to see what the PM kit would do since I sanded down the seal. It wasn't really a fair comparison before since I sanded the seal down after taking the PM kit out . Well guess what!
With the PM kit back in it and the seal sanded down it is shooting the 8.4 JSB at the exact same velocity as the Twister spring. And with a much nicer shot cycle. I hit 845 fps with the PM kit and 8.4 JSB. I hit 842 fps max with the Twister spring and same pellet. So it looks like my tight seal was holding the fps back quite a bit as it went from 780 to 845. I shot about 25 shots over the chrony just to double check and they were all from 835 to 845 and the variance was probably me not placing the gun exact every time.
I'm a happy happy man.?
My advice, which isn't worth much, would be to put the promac kit in and be done with it. If you're on a tight budget then the Twister spring would be a good option for a lot less money, but a harsher shot cycle. There may be other tuning things to do with the Twister to help with the shot cycle but since it is so long and fits tight there isn't a lot of room to play with.
My opinion only.
You scored! You won!
I may still try the Twister spring and leaving it cocked longer for the simplicity of a 1-piece installation and a lower price.
I'm not afraid to leave it cocked in 4 hour increments, so I'll probably try that. That's assuming he still has any when the time comes that I want one, since he says he has them on "closeout".
Thanks!!
