Different reg setting, same FPS, wildly different results?

[carlos_hathcock]

Had my Impact M3 shooting Nielsen 24.8 OK and Zan 25.5 really well at 110 bar 2nd reg. Changed reg to 120 bar, adjusted hammer for same FPS and Zan’s were terrible and Nielsen’s better. Slugs that were good at 995 FPS now wanted 950 FPS with the higher reg.

So the upshot of all this is it seems that it’s not just one velocity per projectile for your rifle. It’s one velocity per projectile per reg setting, and any particular projectile might not perform at your current reg setting no matter the FPS.

Have others experienced this or have thoughts on it? If the above is true then this all got a lot more complex.

 

[Airgunmann]

Barrel harmonics could change with higher reg pressure and stuff so yeah it's not really just plug and play

 

[Airgunmann]

Each gun is a little bit different to as to what it likes

 

[NAProf]

This is just a possible explanation. When you raise the pressure and adjust the hammer spring tension you may be moving yourself into the region where you are blowing too much air down the barrel. There is a point at which the pellet doesn't go any faster when you raise the pressure and up the spring tension. The max speed of the pellet or slug is ultimately determined by the barrel length. Having lots of air coming out of the barrel after the projectile leaves it will cause disturbed air flow and will affect your projectiles accuracy. May I suggest looking at some tuning videos that talk about this effect. Sub 12 Airgunners is a You Tube Channel from the UK which is very good for the way the guy (Jeff) shows hands on how to do things. His tuning video (for a Crown MkI and for Sub 12 FPE) is good for showing how to find the "sweet spot" when tuning for velocity. I am attaching a link to it.
Cheers,
Greg

 

[Vetmx]

You have taken a legit step forward in understanding things. You always understood speed can be important. Now you are learning how important air delivery is. If you are fortunate enough and don’t run out of money or patience, you will discover quite a few more pieces to the puzzle.

 

[Trucker3573]

Agree with what others have said. I think it’s a combo of barrel harmonics and how long the valve stays open/how much air is behind the pellet. Exactly why tuning is so interesting and fun to me.

 

[Stubbers]

Pressure has various effects at different settings, as others have note, harmonics. Add to that the force on the back of the pellet which may form your skirt to the barrels groves better.

 

[DBlue]

I just got a new MK3 a week ago and I have been trying different methods for tuning it. There are several different ways to tune it and just about everyone has their own method....some say start at these #'s others say no, start at these....it's quite evident that there are more ways than just one to get these rifles tuned and every gun is not going to be the same. I can only say about my own experience in the short time I've had this rifle and I have tried several of the most popular methods that everyone is talking about. The one method that has worked the best for me came from the guy at Michigan Air gunners... he has a youtube video explaining how he tunes.....first you have to decide which speed you are wanting to tune to and instead of starting with low settings and working your way up, you start out with a lower 2cd reg setting with all the other settings maxed out and start with adjusting just your 2cd reg up until you reach your determined speed and then start adjusting the other settings down one at a time to reach the point to maintain your original set speed. With my rifle this method has worked the best for me and my gun shoots with the best accuracy that I have got out of it doing it this way. Check out that youtube video and try it exactly as he explains it....I think anyone that's trying to get their gun tuned will be pleasantly surprised tuning it this way.

 

[Chukar60]

It has been my experience that I start low and work up to the speed I want. When I say low, I mean the lowest reg pressure I can use to drive a projectile at a desired speed. I have tried the high reg pressure lower hammer weight method and all I got for my troubles were higher standard deviation, shot strings that look more like a pattern than a group.
The culprit? Too much air. Back the reg down and fiddle with the reg until balance is achieved. The gun is quieter, delivers a smoother shot cycle and accuracy improves dramatically. You will also optimize your shot count.
You will enjoy your gun more if you aren’t beating the crap out of it by hammering the valve too hard trying to fight over pressurization of the plenum.

 

[DBlue]

The method I described is, set the hammer wheel to 16, turn the micro adjuster as far towards 5 until the gun will not cock, then start turning the micro adjuster wheel back until the rifle will cock and leave it there.....then set the 2cd reg to about 90 and turn the front valve all the way out past four.... (where line 6 would be ,if there was a line 6). If the speed you are wanting is say, 920 fps., start shooting with the 2cd reg at 90, if the speed is low, turn the 2cd reg up to 95, keep shooting and bumping up the second reg by 5 bar until you reach the speed range you are looking for, once you reach your speed, leave the reg set there. Start shooting again and move just the power wheel one click down at a time until you find the point that your set speed starts to drop and then click it back one click to where your speed was the same. Start shooting again with only moving the micro adjuster about 4 clicks at a time between shots, back towards 1 until you see your speed change and leave it set where your speed stays the same. The last thing is, start shooting groups while turning the front valve back a half turn at a time between shots until you see a change in your speed....you will actually start seeing your groups tighten up between shots while adjusting the front valve. By tuning my MK3 just like this, I'm shooting one hole groups at 50 yards with JSB MK2's 33.95 pellets at 915fps. I'm getting over 60 shots per fill , the gun is no where near being over pressurized. My final settings after tuning like I just stated is: 1st reg= 150 bar 2cd reg=100bar Hammer wheel= 8 micro wheel= 3 1/2 Front valve= in the middle of the 3rd & 4th line

 

[Stone02]

If you are fortunate enough to stumble upon a good tune. Stop, leave well alone.

 

[Vetmx]

If you are fortunate enough to stumble upon a good tune. Stop, leave well alone.

I agree with this 100%. But this is what it says above door #2 in slug land. Behind door #1 you learned how to find good groups. Once you enter door #2, you have to learn how to find consistency. How do you make or keep your gun on that fine line long term so you can trust the gun every time you grab it. Some guns will do it with just a perfect regimen of bore maintenance. More complicated guns can require more scrutiny or are just never able to do it until you figure some things out. The number one mistake guys make with bullet shooting is putting any faith in what someone says or they see in a video that doesn’t come from a long term owner of that particular gun. Anyone with half a brain can find a setting good enough to make it seem like they know what they’re doing. The big question is how is that tune and gun performing months from now. You almost will never know that. The reason? Because YouTube Willy already moved on to his next toy or the average forum Joe‘s gun just won’t shoot that slug and tune good anymore. Those are the things that go unsaid and keep the wheels of the industry spinning round and round with money spent chasing.

 

[Stone02]

I've had numerous guns of one type or another. And the non-consistency of airguns is about as frustrating as with rimfire. My guess is it's a lot to do with ammo' non consistency.

 

[Headshots]

Different length barrels are going to perform best with different air deliveries. Short barrel, a quick burst , longer barrels like more dwell times. Longer barrels are usually more efficient and can achieve the same fpe at lower pressures.

 

[weevil]

Two comments from me. First, be aware that too much hammer at low reg pressures can result in reduced speed. It’s always a good idea to check each time with the power wheel a few notches lower.

Second, I see very little patience with tuning these days. Too many people think they can take their new gun, set up a canned tune and immediately get the same accuracy or ES as some YouTuber. It fine to have a suboptimal tune for a while. Instead of fiddling endlessly, put a few hundred shot cycles through to allow the barrel to get leaded in and the reg to settle. Then find the sweet spots after it’s all bedded in.