Steyr LP 10 Velocity Variations

[Gwhite]

One of the students I help coach complained that her Steyr was using up a lot of air. I checked the cylinders & the pistol for leaks overnight, and everything was fine. The cylinder gauges both read a bit low (10 to 20 bar out of 200), so part of it was that it looks like they are lower on air than they really are.

The pistol was bought used, and I figured maybe somebody cranked up the velocity. I got out my Combro chronograph, and the averaged velocity was a bit high, ~ 535 fps, but I also noticed a lot of variation.

I adjusted it down about 1/16th of a turn, and the average velocity dropped, but the variation was even worse. I got velocities ranging from 506 fps to 534. I've tested my own Steyr, and the maximum variation I've seen was maybe +/- 5 fps.

I'm guessing it needs a good overhaul, but I figured I'd check the forum for thoughts & opinions before I box it up & ship it off for service.

[Ramon OP]

When I got my Evo 10 repaired the gunsmith said it was a problem of the pressure regulator and that he was seeing more of these issues than with other brands.

[Gwhite]

I'll look into getting it serviced.

I did a little digging into the original concern, which was too few shots on a fill. Steyr claims you should get 170 shots off a full (200 bar) fill.

In the process of test firing, I fired 44 shots and used ~ 35 bar of pressure. I'm not convinced it's perfectly linear, but if it was, then 170 shots would be ~ 135 bar, so that all sort of hangs together. The velocity was set slightly high, and that could account for the difference.

I think the student's concern was partially because her cylinder pressure gauges read low, and she was also worried about shooting much below 100 bar on the gauge.

What I can't find in the manual is how low the pressure in the cylinder can go before you lose pressure regulation. The older cylinder gauges used to have a yellow section that looks like it starts at around 60 to 70 bar. The new cylinders have a green region that basically goes down to zero, with markings down to 60 bar.

Steyr Cylinder Old & New Gauges (sm).jpg (45.04 KiB) Viewed 5294 times

Does anyone know at what pressure the Steyr regulator loses consistency?

[David M]

According to Steyr...
"The air for actual shooting is drawn from the compressed-air storage cylinder and reduced by a reduction valve to the steyr pistols working pressure of about 55 bar. According to Steyr air pistol their compressed-air cylinders have a storage capacity for about 180 shots."

[Gwhite]

Thanks! That's way lower than a Morini will go before it locks out...

[David M]

The Morini regulator is approx. 80 bar, so the lockout should also set at 80 bar.
After lockout if you override performance will drop off in 10-20 shots.
You can still finish a final if locked out mid way.
The regulator pressure depends on the size of the pre charge chamber, Walther is different again.

[Gwhite]

At the risk of derailing my own thread, can the lockout on a Morini be easily adjusted? Mine kicks out at close to 100 bar.

[David M]

yes, but difficult.

[Gwhite]

Well, the regulator is messed up anyway, so I guess I'll send that off for service as well. Even with the velocity screw back out all the way, it shoots at 520 fps & uses a lot more air than it should. That combined with the high lockout pressure, and I can't get anywhere near 200 shots per cylinder.

[wasatch]

Another possible cause of velocity variation could be some dirt in the area of the hammer and hammer spring. Its pretty easy to open that up and clean.

Are the breech and transfer port seals looking good?

Regarding air consumption, is this LP10 by chance a compact?

Long time ago I took apart my Alpha Proj regulator, cleaned it up and replaced an o-ring which helped its consistency. Probably wouldn't need to completely disassemble it (the belleville stack) in order to inspect the plunger o-ring and clean/re-lube. After removing the reg by removing the 4 mounting bolts, open the reg block by removing the 2 remaining bolts and the plunger assembly can be inspected/cleaned.

This post has some good pics of an LG reg which looks similar based on LP exploded diagram:
https://shooting-the-breeze.com/threads ... ase.26163/

This Steyr pdf lists LP & LG reg settings and belleville stack configs.
http://airgunnationforum.s3.us-east-2.a ... 202016.pdf

[Gwhite]

While adjusting a different LP10, I discovered that the results and velocity stability depend heavily on the locking screw. The Steyr video makes it look like you just unlock it, adjust, and lock it again. Unlocking the screw on this pistol dropped the velocity by about 30 FPS. Once I had it adjusted to the middle of the nominal range, the velocity went up over 50 FPS. Tightening the locking screw so that I had some resistance only helped a little bit. I eventually had to unlock and re-lock the screw after every adjustment to get any sort of control. I also noticed that the velocity variations depended on how tight the locking screw was set. When I was done and tightened the screw as much as I dared, I got velocity readings of 520, 522, 519, 523, and 518 FPS.

For future reference, I saw about 60 FPS change for a quarter turn of the velocity screw.

I decided to go back and double check the pistol that I had originally posted about. The velocities I measured after adjusting it were 526, 514, 520, 528, 528, 517, 525, 506, 507, 529, 519, 530, 534 FPS. That's an extreme spread of almost 30 FPS over the last 6 shots. What I don't recall is how tight the locking screw was (if I had it tight at all). My suspicion was that it wasn't very tight, which would explain the variations.

I took 15 readings without touching anything, and got:

Minimum 509
Maximum 528
Spread 19
Average 518.5
Std Dev 5.2

That's a good bit better than it did before. Then I popped the grip off, and checked the locking screw, which was actually pretty tight. I may have tightened it when I gave up on the pistol earlier. In any event, I tightened the locking screw a bit more until it was good and tight and took another 15 readings:

Minimum 513
Maximum 528
Spread 15
Average 521.7
Std Dev 4.5

Although it still varies quite a bit more than the other pistol I adjusted recently, it's a LOT better than I originally thought. The velocity spread is half of what I had earlier, over considerably more samples.

So, the lesson is: Lock the screw down good & tight before taking any final data, and to un-lock & re-lock it between adjustments. Otherwise, you just end up chasing your tail.

What I don't know is:

A) What is the typical velocity variation one should expect from an LP10 in good condition?

B) How much vertical spread does a variation from 513 to 528 FPS actually produce?

[wasatch]

B) How much vertical spread does a variation from 513 to 528 FPS actually produce?

Using time of flight from Chairgun, about 1.3mm.

[Gwhite]

Wow! That's a lot more than I expected. Thanks!

I'm not sure most collegiate shooters would notice any impact on their scores, but that's certainly not going to produce the sort of test targets the pistols ship with.

[seamaster]

1/4 of a pellet head difference might make a slightly larger hole compared to factory pellet target testing.

It was certainly not a "single" hole from factory. So most factory velocity variation is about 5-10? So a difference now of 15 FPS drop of 1.4mm is still very acceptable to most people. Number looks amazing large, but still very, very small drop in height.

[Gwhite]

The holes in the test targets I've seen are typically not that much larger than a pellet. Then again, I had roughly twice the sample size of the groups on the test targets. so maybe they are comparable.

The team I coach has 26 new Hammerli AP20's. A couple other coaches using these have reported problems with the velocity locking screw not being tight enough, and over time, the velocity drops. To get a baseline for comparison, I measured the velocity of 6 shots on 13 of the pistols last night. I'll post when I get data on all 26, but so far, the best of them are as good as the Steyr's, and the worst aren't that much worse.

[Gwhite]

Another data point:

I just bought a used LP10. It appeared externally to be in mint condition, but it seemed unusually load. When I measured the velocity, it was running around 165 m/s (540 fps). I started to adjust it down to the nominal range of 155 to 160 m/s, but noticed that every time I fired it, I could feel a puff of air on my trigger finger. I replaced the firing port seal (the horizontal one just behind the breech), and the breeze went away. I couldn't really tell that it made that much different in the velocity.

In any event, I had to back off the velocity screw by a little over 1/8th of a turn to get the velocity down from 165 m/s to to 157 m/s (514 fps). Earlier, the pistol I worked on changed velocity 60 fps for 1/4 of a turn. This one changed about 50 fps for 1/4 of a turn, or about 15 m/s.

[Rover]

In my pellet accuracy testing using Bill Poole's Morini, I found that accuracy noticeably deteriorated as it approached lockout. I refilled and continued testing with excellent results.

I don't know if this applies to any other Morini's.

Shots per fill on my (then) Steyr LP1 was about 140 at around 525 fps with light pellets. CO2 guns would get well over 200 easily.

Of course, if you want to bypass all these problems and yet have the smallest shot to shot variation, go with a SSP.

[6string]

It's disheartening to read about this problem persisting with the LP10.
Twenty years ago, I ran into the same problem with a few LP1s and an LP5.
On a couple occasions the issue was a cheesy part in the regulator. It was a valve piece consisting of a short length of music wire fitted to a green plastic valve plug. The plastic part cracked on both occasions.
Seems that the introduction of a newer (and more expensive) model would warrant an engineering change.
At least getting access to, and replacing, the part was easy enough.

[brent375hh]

You may possibly had the same issue I had. See my post under a similar title.

[spektr]

I do not understand why people allow the regulators and orings to dry out. I do not directly oil the gun, but I periodically apply a touch of silicone based oil to the tank threads, it makes it far easier to put the tank on and odd AND the oil slowly migrates into my regulator and it shoots very consistantly....... The issues I see you describe along with my previous crusty tank valve problem reinforces 2 things in mind. First, we must gently lube these creatures.
Second, Extended periods of storage, like a few weeks or longer, should have the tank unscrewed to unload the regulator and drainiing the tank is probably a great idea. Unscrewing the tank also means unseperaring the threads completely to protect the threads from excessive cam out forces if its case is bumped or dropped...