TargetTalk

I just tested my EVO-10 (Compact) through the chrony and was surprised to find a much larger extreme spread between velocities than I'd expected. Especially with a regulated gun.

I did 80 shots and started from full about 190 bar down to 60 bar.

Results were average velocity of 491 fps, with a low of 466 and high of 509. Extreme spread of 36.10 and standard deviation of 10.7.

After the 80 shots, velocity started dropping really rapidly, and by shot 89 it was only 396.2 fps.

Would you consider this normal? Shouldn't a regulated match quality gun like this give much more consistent velocities with a lower extreme spread?

What weight of pellet are you using ? I believe (from the Steyr agent in the UK), that Steyr uses JSB Match green tin at 7.72 grn to test and produce the shot card.
Using RWS R10 7 grn I get the following after 90 shots from a full (200 bar) compact cylinder(LP10 Compact pistol)

91 161.7 530 fps
92 162.2 532
93 161.3 529
94 159.5 523 fps
95 158.2 519 fps
96 155 508
97 154.6 507
98
99 151.4
100 150.1 492 fps

You should get 94 safe shots from a compact cylinder.

Silvershooter wrote:What weight of pellet are you using ? I believe (from the Steyr agent in the UK), that Steyr uses JSB Match green tin at 7.72 grn to test and produce the shot card.
Using RWS R10 7 grn I get the following after 90 shots from a full (200 bar) compact cylinder(LP10 Compact pistol)

91 161.7 530 fps
92 162.2 532
93 161.3 529
94 159.5 523 fps
95 158.2 519 fps
96 155 508
97 154.6 507
98
99 151.4
100 150.1 492 fps

You should get 94 safe shots from a compact cylinder.

I'm using JSB Match Pistol pellets, 7.33gr.

You're really getting higher velocity than I am. And you say yours is a Compact also? By shot 80, the velocity on my pistol is already down to 466 fps. By shot 89 it's under 400 at 396.2 fps. For yours, even by shot 100 your pistol is considerably faster than mine. I don't get it.

And if I were to tune up the velocity a bit, then it would use even more air (wouldn't it?) and thus I'd get an even lower shot count?

It sounds like it might be a regulator problem.

If you must have uniform velocity, a SSP is the ONLY way to go.

Rover wrote:It sounds like it might be a regulator problem.

If you must have uniform velocity, a SSP is the ONLY way to go.

I don't know if I need uniform velocity! As you're aware, I'm a newcomer to this and the EVO-10 is my first match pistol. So what I'm really asking is does the extreme spread of velocity across 80 shots sound normal for this model (high-end, regulated) gun? And is my shot count of about 80 good shots normal?

If so, I won't worry at all about this. I just don't know.

I believe that at least LP10(E) has its regulator set to 70bar. I'm not certain at which cylinder pressure regulator starts to cause pellet velocity to drop, but I tend to change cylinder at about 80-100bar.
I have not bothered to do any velocity or pellet tests since it is me causing those bad shots.

My CM162EI needed to be dry fired with air 1-2 times before sessions to "seal correctly". Might be the case but I never had spreads like those on my newer LP10 (didn't chrony my older one but I never saw a POI shift). The SD isn't that high but the extremes seem to indicate a problem, especially if it's before getting a lower pressure from the cylinder. Are you certain there are no leaks? All o-rings properly lubed, etc? It's definitely not the regulator, as you got a new one this summer, right? Barrel well adjusted? At this point it seems you've got way too many issues with this gun, so, I'd simply send it back to Steyr or Krale. Or Cibles Canada if you're in Montreal. They do great work.

EDIT: Misread the part about shooting down to 60 bar. Of course you'll see a drop in fps. Steyr should've the lockout like Morini to indicate low pressure. But doesn't Steyr say you should get 100 shots out of a short cylinder? Otherwise, seems like you have a perfectly fine pistol. Enjoy!

And you say yours is a Compact also?

Yes a compact. My 91 - 100 shot has a difference of 38 fps , 91 - 96 22 fps.

Did you not have to change your regulator once already ?

Silvershooter wrote:What weight of pellet are you using ? I believe (from the Steyr agent in the UK), that Steyr uses JSB Match green tin at 7.72 grn to test and produce the shot card.
Using RWS R10 7 grn I get the following after 90 shots from a full (200 bar) compact cylinder(LP10 Compact pistol)

91 161.7 530 fps
92 162.2 532
93 161.3 529
94 159.5 523 fps
95 158.2 519 fps
96 155 508
97 154.6 507
98
99 151.4
100 150.1 492 fps

You should get 94 safe shots from a compact cylinder.

I think these figures are m/sec not feet.
150 m/s = 492 f/s
For velocity 450 f/s is too slow , 550 f/s is too fast.
An average between 480-520 is fine with a SD or MAD of 10 f/s.
The pressure regulator will only work if the tank pressure is above about 80 bar,
so if the tank falls below that the velocity will also drop quickly.

Lower the tank gets, the longer it will take the regulator to create the required pressure for the next shot.

And it's obvious that the last shots are at a tank pressure that is inadequate to generate the desired velocity.

An aside: My paintball days have me wondering if someone should contact Tom Kaye at Airgun Designs to see if he ever considered using his regulator and on/off design in pellet pistols.

I think one ought to put things into perspective and not get too worried about chrony data.

1. The number of shots one would normally take in a match would rarely exceed 80. That's 20 sighters and 60 scoring shots. It's not going to happen in a match that you will have to squeeze out as many shots as possible from the tank, unless you have nothing to refill your tank from.

2. The relation between the variation in muzzle velocity and the drop of a pellet at 10 m is relatively small.
e.g. Using a simple ballistic calculator (B.C. = 0.05)
m.v. = 152 m/s (500 fps) : drop at 10m is 21.1 mm
149 m/s (490 fps) : drop at 10m is 22.0 mm

The difference in pellet drop is 0.9 mm. Roughly speaking, for every 5 fps change in m.v., the difference in pellet drop is between .3 and .5 mm, for m.v. between 460-540 fps (140-165 m/s).

Such a variation is not going to change your scores by much.

I think that it's more likely that one would experience optical/visual effects during a match that will require sight adjustments over and above those necessitated by variations in muzzle velocity.

3. Finally, some caution is advisable when gathering and interpreting chronograph results. The m.v. spread one "measured" may not be 100% due to the equipment. It's already been mentioned that too-rapid shooting will affect the pressure and resulting m.v. If the gun is not solidly clamped, chronograph readings can change by quite a bit due to the shooter's own movement. Even if you think you are holding the gun exactly the same way every shot, there is a variation in gun movement that might be reflected in the chronograph reading. This effect is probably small with airguns, but I wouldn't discount it unless someone has data that shows otherwise. If I had time I'd test it with my own equipment.

From my records of a few years ago: ten shots from my own LP-10 averaged 446 fps, std dev of 5.5 fps and extreme spread 19 fps. I didn't have the gun clamped when I was testing it. I was using 8.2gr match rifle pellets, the gun hadn't been cleaned; the compensator assembly is tuned to 7.7gr pellets and may have had a bit of dust or grit in it. All those factors could easily account for the variation in muzzle velocity.

I've tested one of my rifles that fired 10 shots into a ragged 1-inch hole at 100 yards. The chronograph indicated an average 1426 fps, sdev 22 and extreme spread 69 fps! The reason I tested with the chrony was to check my reloads against the tabulated reloading data, not to convince me of the accuracy, which was determined from the target.