Got a question for some of you. When tuning a certain projectile are you only searching for a certain speed/FPS reading that gives you the best group? Reason I'm asking is on my avenger I am planning on leaving the regulator set at it's max 2900psi and only using the hammer spring to tune with. My question is say I have 2900 psi and hammer spring a couple turns in and reach 900 FPS and I can reach the same FPS with the pressure at say 2400 psi with hammer spring all the way out. Any debate on which one is more accurate? I don't care about air usage or efficiency.
Pressure vs hammer spring at same FPS
- Thread starter revenger
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how about extreme spread, do you care about that? I tune for JUST under max velocity for the reg pressure, if it is to fast, I lower the reg pressure and re-adj the hammer spring to the new, just under max vel.
I find if you just lessen the hammer spring and leave the reg pressure high, you create an unbalanced condition that yields a higher velocity spread which can lead to poorer accuracy
just my two cents worth, do what makes you smile and works for you
I am not a person who wants to tune for this pellet and then want to tune for that slug and jump back and forth, just because the gun has those features, I set it and leave it. I have several guns and several tack/nail/sledge hammers, different power level guns and different hammer sizes, each has a range of usefulness.
I find if you just lessen the hammer spring and leave the reg pressure high, you create an unbalanced condition that yields a higher velocity spread which can lead to poorer accuracy
just my two cents worth, do what makes you smile and works for you
I am not a person who wants to tune for this pellet and then want to tune for that slug and jump back and forth, just because the gun has those features, I set it and leave it. I have several guns and several tack/nail/sledge hammers, different power level guns and different hammer sizes, each has a range of usefulness.
jarmstrong is right. If the regulator pressure is set high and you back off the hammer spring tension well below the plateau, you will get a poor extreme spread. At short range it may not be very noticeable but it will negatively affect groups at a distance.
For best results, gradually increase hammer spring tension until the velocity no longer increases, then back it off to about 95 - 97% of that maximum. If the resulting velocity is higher or lower than you wanted, adjust the pressure accordingly and repeat.
For best results, gradually increase hammer spring tension until the velocity no longer increases, then back it off to about 95 - 97% of that maximum. If the resulting velocity is higher or lower than you wanted, adjust the pressure accordingly and repeat.
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Yep, good advice above. In initial tuning, speed is speed, and the pellet doesn't know how it is generated. Once I find the velocity I want, based on accuracy or fpe, or whatever, then I tune for the proper balance, adjusting the reg set point as described.
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As Vetmx confirms, generally yes. I’d just like to add since there is usually vastly more bore friction with slugs, a high regulator setpoint with a light hammer strike (short dwell) is likely to produce an even worse impact on the ES with slugs than it does with pellets. So in the course of testing if the speed fluctuations seem objectionably high, try a little more dwell. Lubrication may also help.
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All good points. Right now i got the psi maxed out and hammer spring all the way in so max speed and my fps spread has been really good actually. Running the jsb 33.95 mk2's about 73 FPE and holding a good group at 30 yards. Now I'm trying to find the slug the gun likes most. I don't mind having multiple tunes for my favorite projectiles but I really just want to leave the regulator maxed out and find best hammer spring settings . I just didn't know if there was a pressure thing vs time of valve being open that was better or not.
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You can always do what you want with your airgun. But getting the regulator setting matched up with the hammer spring setting seems to really help the gun shoot much better. I am not an adherent to the "95-97%" rule but I do look for the hammer spring setting that gives me maximum velocity for the regulator setting but I then try settings a little more and a little less than that setting. On my Avenger going a little over the max hammer spring setting for velocity significantly reduced group size. On at least my last two P35s it did not seem to make a difference. I think the 95-97% is to maximize efficiency.
I first test a variety of pellets to find the ones my gun likes best. I use a reasonable velocity for this, not over 900 fps and at least 700 fps, but not necessarily where I want to end up. I've consistently found that the pellets that shoot best continue to shoot best when I raise or lower the velocity a little. Bad is Bad and Good is Good. Slowing them up or driving them harder doesn't change things - when you stay at reasonable speed for the projectile. Then I adjust the regulator to give me 800-900 fps and get the hammer spring adjusted to support that regulator setting. My Avenger regulator is set to about 2000 psi and I'm shooting FX 25.4s at 930 fps. I think that's a bit fast for pellets and my limited testing at longer range supports that but I rarely shoot the gun and need to do more testing. I'll probably adjust the regulator to drop velocity to more like 875 or I'll switch to using 33.95s. But it shoots very well at 25-35 yards. So I've left it alone.
I doubt you are getting more velocity at 2900 than you would at 2500, maybe 2400 psi. I've tested mine up to 2500 and the benefit of more pressure was rapidly decreasing. I never found a slug my gun likes, I hope you have better luck. Maybe it was the way I was tuning it.
I first test a variety of pellets to find the ones my gun likes best. I use a reasonable velocity for this, not over 900 fps and at least 700 fps, but not necessarily where I want to end up. I've consistently found that the pellets that shoot best continue to shoot best when I raise or lower the velocity a little. Bad is Bad and Good is Good. Slowing them up or driving them harder doesn't change things - when you stay at reasonable speed for the projectile. Then I adjust the regulator to give me 800-900 fps and get the hammer spring adjusted to support that regulator setting. My Avenger regulator is set to about 2000 psi and I'm shooting FX 25.4s at 930 fps. I think that's a bit fast for pellets and my limited testing at longer range supports that but I rarely shoot the gun and need to do more testing. I'll probably adjust the regulator to drop velocity to more like 875 or I'll switch to using 33.95s. But it shoots very well at 25-35 yards. So I've left it alone.
I doubt you are getting more velocity at 2900 than you would at 2500, maybe 2400 psi. I've tested mine up to 2500 and the benefit of more pressure was rapidly decreasing. I never found a slug my gun likes, I hope you have better luck. Maybe it was the way I was tuning it.
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I have my gun opened up alot so it will breathe! Mine will keep getting faster all the way up to max regulator pressure now. In stock form I found the 2400 psi it seemed to stall out. Now with the gun ported and all the work done I think the air flow is good enough to utilize the higher pressure now. The jsb 33.95's shoot really well out of the gun. I originally thought it they would do best around 870 fps but they are doing great over 970 fps too. Some of the lighter slugs have the ability to break sound barrier and I know that is bad for accuracy. My goal is to shoot everything at max power to find best groups and tune from there. So far a couple of NSA slugs and Zan slugs are shooting well too.
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You will find on that avenger you can turn the reg down from 2900 psi and still achieve the guns maximum capability. I mean if you don’t care about shot count maybe it doesn’t matter? To me durability could play a role as well? Why make the gun work any harder by running at any higher of a pressure than necessary? You should check out AEAC on YouTube about the avenger. Great tuning advice there.
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I will run another test on it but my gun is not stock and can produce over 80 FPE. When I kept raising it the other day the speed kept going up especially with heavier slugs. Air usage I don't really care about as I just switched over to a 700cc bottle. I also just got a Benjamin recharge compressor that can take the gun from 2900 psi to 4500 psi in just a few minutes.
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Maybe so. I don't intend on any 100 yard shots at game right now but maybe in the future. 50 yards and under is my target range.
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Another thing to check is accuracy in windy conditions. That is where I think my Avenger may have an issue with FX 25.4s at 930 fps. Ted of Ted's Holdover channel reported slowing 33.95 down into mid 800s for 100 yard benchrest competition. Knowing your gun is ported makes the ability to get something out of higher reg pressure make more sense to me.
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I have seen that there is window for speed that bucks the wind better. I also just watched a video of Ted's Holdover where his BC kept getting higher and better accuracy with some slugs at around 1100 fps. The avenger in my opinion is definitely a "pellet" gun but I am going to test like 20 different slugs to see what it likes.
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Did you ever end up getting a database of results from your 20 different slugs you tested? I've got NSA 20.2 gr and now 17.5 gr in .216 , .2165, and .217. I tried the 20.2 out but didn't have mine shooting fast enough (was testing other 18 gr pellets at the 850 fps range so slugs were way slow) but that weight was all over my target, except for 3 .216 that randomly got a decent group at 30 yards, but they shot way off (2 o'clock like 8" high) where I was zeroed. .217 was tight but from what I read that's what it should be to engage the rifling.
Anyway, just wondering if you found slugs that work since I have yet to really try mine.
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One thing I would also consider is the shot cycle. When you have a really high regulator pressure you need a really strong hammer spring setting. This in turn makes cocking harder and also produces a rougher shot cycle. This IMO would negatively effect accuracy and it's holder to hold the gun steady when you shoot.
Listen to what's been said regarding the 95% rule. It will give you smoothest shot cycle and best accuracy. But you may not have to go there right away. Find out what speeds and projectiles you want to shoot and then start tuning down the reg for that projectile and speed.
Listen to what's been said regarding the 95% rule. It will give you smoothest shot cycle and best accuracy. But you may not have to go there right away. Find out what speeds and projectiles you want to shoot and then start tuning down the reg for that projectile and speed.
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