TargetTalk

Hi everyone!
This is my first post here and after hours of browsing and gaining through various topics from time to time,I finally decided its about time I joined.
So anyway-here goes.As an air/free pistol shooter,I have played a few internationals and a couple of W.Champ.'s(mostly as a junior :P) however I'm still clueless with regards to the inner workings of a Steyr LP10e,specifically in relation to velocity variations as I have almost never encountered this problem before,(just once--going back to the LP-1 days and our junior coach had taken care of that at the time)
So here is the issue-while training(LP10e) I noticed a significant change in the sound(like a low pressure sound) and barrel vibration freq. after about 30 shots on a full cylinder and sure enough about 10 shots later I had a nice 'dropped group' at the edge of 7th ring.Took out the cylinder,grip and circuit to have a look and after deciding not to tamper with the velocity screw, reassembled it.Fired a couple of more,they still dropped.And then---the 3rd shot--NORMAL! in sound and on target.And 10 shots later a 97 with a couple of early nines,which was pretty much the same avg.as before the dropped shots happened.I dont get it!Why would something this drastic occur for only a few shots then suddenly correct on its own..??(Reassembly didnt have anything to do with it,..I think..)..Will appreciate any answer attempting to shed a light here..thanks!.--Varun

I hear about this problem last 5 years. It is not mass problem but I hear about it from time to time.

In most of the cases - cause is the part No. 18 (valve complete). Surface roughness and burrs.

[quote="ruig"]I hear about this problem last 5 years. It is not mass problem but I hear about it from time to time.

In most of the cases - cause is the part No. 18 (valve complete). Surface roughness and burrs.[/quote]

Thanks for that man!Helps to focus on what to check for now.Right now I am in process of conducting a 100 shot test on a velocimeter to see if it happens again.Will post if a breakthrough is made.

Sounds like a regulator /valve issue. Do you have a chronometer?

UPDATE: So in the speed tests,the velocity changed from about 360 fps avg. for 1st 15 shots and sharply dropped to vary between 338 to 360 fps from then on.
After about another 50 shots it is now firmly stuck at a low 350 fps avg = 106 m/s. And now its sounding the same all the time i.e a low pressure sound.So whatever was causing the variation seems to have given way.
At the steyr site,the speed specified is 155m/s.From what I gather from the forums it seems for some people it varies a bit from that and some people have a different adjustment as well.
Now the question is- Should I go about getting the valve repaired ? Or try to change the velocity through the screw? (Will need directions for the velocity change as I have never done it before!).Thanks a lot.

106m/s is extremely low.
I would first try to adjust the velocity

Here are steyr's instructions on how to do it.

http://www.youtube.com/watch?v=EknIAlut_hE

If it does not work you could have a problem in either the regulator or the hammer.

My old tests (10 Euro pellets VS 2 Euro pellets) measured by cb-625 (Mk 4):

Wow, I never thought the cheap pellets would have such a dispersion.
Although I use H&N Final Match Rifle pellets I was under the impression that the difference was negligible. It seems that this is not the case, at least for your pistol.

@taz: Thanks a bunch.Range is closed now anyway,so I will try to adjust it while checking speed tomorrow.Though the screw is not turning more than 1.5 turns right now,but the sound is significantly different.Will add tommorow if resolved.
@ruig: Amazing!Thanks for that--i mean i knew pellets factor in as well but thats some variation,anyhow I use H&N only so thats that.
P.S-Those speed variations make mine look gigantic in comparision!!

What is interesting with Igor's chronograph tests is that there is no correlation between pressure and velocity in the 4.49mm pellet test from 200 bar down to 170 bar and in the 4.50mm pellet test from 170 bar down to 140 bar!

It would be interesting to have continued each of these tests to find when the correlation occurs (ie. at what pressure does the velocity begin to drop and what is the correlation between the reduction of velocity and the point of impact on the target (and if the group size gets bigger as the point of impact becomes lower - but this is an academic exercise because no one should allow the pressure to fall this low.)

If these two 30-shot tests were done from the same air cylinder (and I assume they were because of the stated pressure readings at the beginning and end of each test), this represents a 60-shot match (without sighters). How many more shots can be fired from this cylinder before the velocity, point of impact and group size begin to change?

Obviously this depends on a number of factors, including the velocity/pressure adjustment setting. It is something that we all should know about our air pistols. I seem to remember reading somewhere that the Steyr can fire about 200 accurate shots from a fully charged (200 bar) cylinder. I top mine up after each 60-shot match/training so I have no idea what the critical pressure is.

So, another job for when I'm next at the range is to find out at what cylinder pressure I can start blaming the pistol for the poor shots!

jliston48 wrote:What is interesting with Igor's chronograph tests is that there is no correlation between pressure and velocity in the 4.49mm pellet test from 200 bar down to 170 bar and in the 4.50mm pellet test from 170 bar down to 140 bar!...

...So, another job for when I'm next at the range is to find out at what cylinder pressure I can start blaming the pistol for the poor shots!

The regulator reduces the pressure to somewhere in 50bar range, so until the cylinder drops to that or below you shouldn't see any change in velocity or accuracy. Sorry can't blame the pistol just yet!

Also, those groups that Ruig shows are not that good, I wonder how the pistol was held?

For comparison here is a test with a Morini Airpistol in feet/second.
1/ 499.2
2/ 494.2
3/ 492.2
4/ 496.0
5/ 492.6
6/ 499.0
7/ 493.1
8/ 498.4
9/ 491.4
10/ 495.6

Max 499.2 fps
Min 491.4 fps
Extreme Spread 7.8 fps
Average 495.1 fps 150.9 m/s
Std. Deviation 2.6 fps
Mean Avg. Dev. 2.4 fps 0.731 m/s

A good airpistol should not vary more than about 2 m/s, max 3 m/s.

With pellet testing I found that the group was nodal and that by small velocity changes the group size can be altered. There was a best group at about 145 m/s and again at about 157 m/s.
I reduced to 146 m/s and my pistol will hold a one hole group 1.25-1.5 pellet dia. Minor group changes between pellet brands.

Interesting!

I remember a test the NRA published in their "American Rifleman" magazine some years back. They were testing a SSP air pistol. I don't remember which, but I suspect it was a FAS 604. The extreme spread was two FEET per second (not meters), or less than one third what "a good air pistol" should clock.

I agree that accuracy is nodal, but extreme spread (unless gross) has little effect on accuracy.

Many years ago the FWB 100 over a chronograph gave the best Ext. Spread of any pistol I have ever tested.
The pump gun's may well be better than the pre compressed guns with regulators for consistancy, but rule changes, reduced match times and old age take those pistols out of the game these days.

Shortly after getting my LP10 years ago I talked to Scott P. about velocity and accuracy. This was at a match so when I was done shooting he set my velocity at 550 fps (167 m/s) and then I took it home and put it in a vice and started testing and adjusting the velocity from there.

550 fps is a good starting point for velocity to start looking for a good group. I am sure there are other nodes out there you could find. At 550 fps you are not going to shoot 200 accurate shots if this is important for you. You need to also try out different pellet sizes at different velocities.