I have a custom HFT-500.
This rifle was tuned by Will Piatt to 17.5 fpe, Shooting 10.3 gr pellets at 870 fps. I developed a leak and replaced all the O rings in the gun. I put it all together and have been shooting it to make sure the repair is complete. And no more leaks.
The next thing I did was chronograph the pellet speed. And found it to be 850 fps. I took the rifle to the range and the rifle is amazing. Gives me the giggles putting together one hole groups at 40 yards with 20 mph wind. It is really good.
The regulator is set to 100 bar.
I had to replace the valve block and valve. The transfer port was enlarged by Will among other things. And I did the same modifications with the new valve block.
it uses a Lane regulator and i set it the settings included with the gun.
I can adjust the regulator up and see if that increases the power.
I can also adjust the hammer and valve springs but I believe I have done that and now I need to adjust the regulator.
My question is Should I do that?
the HFT-500 shoots 12 ft lb all over the world. I am at 16 rather than 18 ft lb. With standard deviation of 2 and even shot strings of 50 shots it is never more than a SD of 4
i like the 10.3 gr pellets. Do I need the extra 20 fps?
I want to set it and then do the scope work
I THINK that only you have the answer.
NEVER tune a gun to a speed (unless you are making it "legal" within a country or a rule.
In GENERAL terms, the power output is adjusted via the regulator within broad bands. The hammer is there to assist you in the SMALL changes required to make the gun shoot ACCURATELY and CONSISTENTLY (PRECISELY in metrological terms).
In an ideal world, that should be the same point, but the world is seldom ideal, so you need to decide what is more important.
For ME (in FT), consistency is more important. If you can achieve true consistency (high precision), then accuracy is a matter of re-setting the sights.
What you need to do is head to the range with a chrono and targets in hand, plenty of air in the tank.
Set a target at 45 yards minimum, 55 would be better.
Shoot 3 X 10 shot groups and document that target (that means add to the target a note about MV's stats and average group size).
Now move the speed up a little using the hammer spring (document, how much of a rotation you put into the hammer spring).
Repeat the 10 X 3 groups and compare.
It MAY happen that you can do this exercise and for every "nudge" of the hammer spring, the MV's will go up at a more or less uniform pace. As long as this is true you can continue adding MV IF the results at the targets are improving. If the results at the target (average group size) is not improving, then you're going in the wrong direction, and you need to BACK OUT in the MV/hammer spring.
IF for every nudge of the hammer spring, the MV's start increasing less OR start going haywire, then you have overshot the natural balance point of the mechanism (more on this further down) and need to back out on the hammer spring a little and increase the regulated pressure.
On the other hand, IF groups improve as you LOWER the MV/hammer spring, then you need to decide at which point it is acceptable to you. It may be that you end up shooting at 12 ft-lbs and then the wind may prove too challenging.
So, only YOU can decide what "tune" you need in your gun.
In GENERAL, adjusting the regulator requires degassing, so it is not easy to test different regulator settings. Even in those guns that have externally adjustable regulators, to REDUCE the regulator pressure requires degassing. You can increase without degassing, but you cannot decrease without it.
According to Lane's documents the regulator was set from factory at 105 BAR's, do you have TWO manometers to measure the regulated side?
Because of the way poppet valves act, there is a "NATURAL" balance point where the opening and closing of the valve happens in harmony between the hammer blow (and continued force on it) and the valve closing forces (mostly the air pressure backing the valve), so it is always "smart" to try to get to that "natural balance" point. But not all guns/barrels perform their best at that point, so, IMHO, the accuracy/precision tests need to take precedence over the mechanical balance.
Good luck and keep us posted!
HM
Thank you
i am shooting in a class that allows sub 20 ft lb of energy.
The accuracy and consistency was extremely good at 870 fps.
the adjustments to the regulator are easy. I just need to remove the regulator and turn the screw and measure the gap.
the balance between the springs is pretty close now and the consistency is also good at 850 fps.
I guess what I’m asking is do Diablo pellets fly better at 16 ft lb or at 19 ft lb?
I have the original gauge on the bottom to measure regulated pressure and a 300cc Air Venturi air tube with a gauge and fill probe at the tip. As I said this gun is highly modified and very adjustable. So I can set it to any level I want.
I am just about to do all the scope work. But want to make the gun adjustments first. If that makes sense?
I'm not saying it is complicated to adjust the regulator. I am saying that it's a process:
Degas, adjust, fill, check, and maybe repeat.
I knew Will P. well, we liked each other, exchanged gunsmithing bits and tips, and shot together a few times. I was probably the first one to insist that he had won enough in Open PCP and he should move to WFTF PCP, LOL!
I now understand that you can actually measure the regulated pressure. That was not clear in your initial post.
Ballistically speaking, MOST diablo waisted pellets have a maximum dynamic stability at around 730-770 fps. BUT that does not mean that you have to shoot, or that they shoot best, at this speed. This just means that the flight will tolerate external disturbances better. It's the reason why MANY top shooters in WFTF shoot at 10 ft-lbs.
It is something I discovered when shooting the H&N BFT. It will shoot VERY well at 734 fps. and the added weight gives it a bit more wind resistance. Same goes for the QYS in 9.56 weight.
When you go to the "Semi-Slugs", that point moves a bit further down the MV line. The JSB's 10.3 seems to have a maximum stability speed of around 875 fps that is about 17½ ft-lbs.
The new "re-designed" Monster (13.4's) seem to like higher speeds, like 900 to 920, and the Beasts, go back to the "semi-slug" region of 875. These impressions come from some testing that has NOT been as thorough as I would like for lack of time, but I would place an 85-95% range of confidence in these results.
BUT, the 20 ft-lbs that are the limit to AAFTA Hunter and Open PCP classes dictates that you CANNOT use the Monsters or the Beasts within the rules at their maximum stability speed.
Having said that, and I hope it is understood that these are general concepts on the ballistics side, not specific recommendations, I would add that I have seen rifles that have great accuracy and precision at 950 fps with the 10.3's. Granted they were FX's special barrels, but it does show that it is possible for some barrels to be accurate AND precise a those MV's.
The ONLY way to know if your barrel will do that is to test it.
IF I was in your shoes, I would set the Reg to 110 BAR's, and then tune for the speed that gives me the best consistency and repeatability at home with the chrono at hand and the compressor close by, then go to the range and tune for accuracy and precision.
About the "scope work", and this is MY way of doing things; more than one has told my I am "cookie", so take it with a grain of salt:
1.- NEVER mix the rangeing of the sidewheel with the trajectory. It MAY work for a while, but if ANYTHING changes a bit, you're done for.
2.- Do the scope work in three different "segments":
a) Get the ranging tape done and check it at different temperatures and lighting conditions.
b) Check the clicks and the verticality of the scope to the bore by testing at different ranges with different hold-offs and/or click setting, this testing does not have to be at the "bestest" power level, it can be made at lower power levels.
c) Then develop the trajectory of the pellet for competition trying to optimize the precision first.
As you can see, you can do some of the scope work now, while the other parts of the process are still being "hashed out".
ALWAYS test in groups of 10 shots and a minimum of 3 groups per setting then average and obtain the sample standard deviation. Do NOT get tricked by the "best group" always look and evaluate using the averages and the sSd's.
At some point in time, you WILL need to get out and shoot in the wind to test if your setting is wind sensitive. If it is, what is happening, MOST PROBABLY, is that your pellets are going out too fast and you need to throttle them back a little. This is easily doable with the hammer spring.
Just in case you are worried because you are shooting AAFTA Hunter PCP, and the ranging at 16X is not as easy as at 35X, (or 80X for that matter)., there is NOT a ton of difference in the trajectory between 850 and 870 fps for the 10.3's assuming they are stable out of the barrel. IF you find there is a big difference, then most probably your pellets are not flying in a stable manner and you need to reduce the speed. But I would doubt that is the case, as Will set the benchmark at that MV.
IF going to 870 means that your CURRENT lot of pellets goes unstable, then your BC will suffer much more than the gain in velocity can compensate.
I HAVE seen MV differences of this range when changing batches of pellet, so I am not sure the difference in your current velocity is a question of the re-seal/work in the gun, or it comes from a different batch of pellets.
-Note to self: proofreading this has made me realize why airgunsmithing is so complicated, ROFL!
Keep well, keep us posted, and shoot straight!
HM
Thank you
I guess my concern is it was set to 870 and now it’s not.
I will raise the reg pressure as suggested.
I am just learning this gun and I have the scope range part done. And I did in cold and have those settings all recorded for reference when the temperature rises.
I will raise the reg pressure and adjust the hammer spring if necessary.
Thank you for the help.
I found this document regarding tuning the Lane regulator. Everything was done but I had a lot of wear on on the seat and a new valve would not seal. I replaced the block and opened up the transfer port to the same size as the original.
but now with this document I am going to go through and check everything. And adjust the regulator to 2.75 mm.
Thanks for reminding me why I deeply dislike AA. ROFL!
As a side comment:
The BEST way to control the power of a simple PCP (non-electronic and decently designed poppet valve), is to RESTRICT the TP.
Properly restricted with self-blocking valves, the "inverted bathtub curve" flattens notoriously, the efficiency goes up and the noise (meaning less wasted energy) goes down.
If you couple that with a regulator, you're almost at the point where you can do whatever you want, just changing the TP's.
IF you add a Free Flight Hammer (FFH), you increase the efficiency and the shot count.
The statement that the regulator does not increase the power output is as big a fallacy as I have seen in printed form.
I do prefer Altaros regulators BTW.
In any case, good luck and keep us posted!
HM
I followed the instructions and checked everything I could. Everything was set correctly. The hammer is cut to 42.3 grams it has a stock hammer spring with two hand made steel washers shimming the hammer spring. Brining the hammer mass back to the 44.5 grams it was originally.
the transfer port is at just under 3.80mm.
I have a new firing valve and valve body. I adjusted the valve spring adjuster screw to 7.25mm in height and about 11.4 lb on the scale. That was the recommended force to lift the valve 2mm
I adjusted the regulator length out to 2.75 mm. I did this by measuring the entire length of the regulator. 2.25 is 1 bar so I added .50 to the total height and now have 1.25 bar.
After double checking everything I test fired about six shots and it was running 855 up about 10 fps and actually acceptable. But I decided to reduce the valve spring pressure one full turn. I did this because at 7.25 mm it was screwed in a lot more than I had it.
I then reassembled the gun and fired ten more shots. All between 878 to 880 fps. Perfectly in the range I wanted it and the way it was tuned when I got it from Miguel.
Now I can put it all back together and start proofing my scope. Building a dope chart.
Round one of testing was pretty good.
the rifle is amazing. Just shooting consistent shots at 50 yards. It’s amazing to me seeing the pellet fly into the target. But I think the regulator pressure is turned up too high.
The regulated gauge reads 100 bar before and now it is reading 125 bar.
I am getting 40 good consistent shots and about 50 before the pressure drops off. And the rifle has a bit of a bark now. I think turning down the regulator is more just a bit would improve the shot count.
I would test with a TP at 3.7 or 3.65 and see where that takes you.
I do not know how you adjust your TP in that rifle. The diagram at : https://www.pyramydair.com/airgun-resources/manuals/air-arms-hft-500-air-rifle-owners-manual.pdf
is not very clear.
In most other PCP's I have worked on, there is a metal element between the valve body and the bolt housing, this metal piece has two Orings and a hole. That hole is the TP and you can make those pieces to suit your power needs.
It is also the part that can become a self-closing valve to increase efficiency and flatten the curve, even without a regulator.
BUT, your HFT500 does not seem to have a part there, so any change would mean altering the valve body and the bolt housing.
Just be aware that at this region of pressures and flow speeds, the SHAPE of the hole is as important as the diameter.
😉
Keep well and shoot straight!
HM
There is a small screw in the right side of the rifles action. I thought it was a bleed screw but it leads into the transfer port. I read that you can make a screw just a bit longer and use washers to then adjust the restriction.
I am going to try reducing the reg pressure first because I think I have it set too high and it’s wasting air.
I reduced the opening .20mm and I will retest tonight.
Hmmmm, interesting!
Not what I would have done, but I have seen it before in other brands (DIANA included when they were building the P-1000).
Thanks and keep us posted!
HM
After a lot of trial and error I cannot get the valve to seal with more than 9 mm of threads exposed. And at 8.9mm I can fill the gun up with no issues. At 9mm it will not fill. It leaks into the transfer port. The instructions say 7.5 mm. But at that setting it is shooting 800 fps.
at 8.5 mm it’s shooting 830+fps and at 8.9 it is 850 fps. All of that is at a regulator pressure about 115 bar.
if I turn the regulator up to 130 bar it is about 870 fps. But I loose a couple shots and my extreme spread goes up.
So I’m going to leave it at 850 fps with 10.3 gr pellets. And dial it all in from that.
850 fps seems to be the speed this gun wants to shoot. I have tried everything including replacing the new parts with the old parts. They leak over night . But with all new parts I can’t get the valve pressure high enough to seal and fill the gun. AND shoot faster than 850.
I think it might be my compressor. It is small and inexpensive. It will fill to any pressure but it starts from nothing.
if I set the adjustment at 9.5mm and can fill the gun everything is fine.
I think if I had a bottle filled to 4500 and could get the air in fast enough the valve would seal. And fill the gun.
What I ment to say is IF I could set the spring pressure at 9.5 mm and get the gun to fill. Then it would shoot 870 fps.
But at 8.5mm and 850 fps it really does shoot well. I was shooting quarter size groups Sunday in 18 mph crosswind. The Gun is amazing.
I am going to get a tank next.
