Steyr LP10 Suddenly Died...

[Gwhite]

Good to know! Thanks!

[argus]

Even if the O-ring is "new"....

Thank you, I'll give that a try.

.... I'm also going to assemble a pressure test gauge so I can verify the front screw setting if I need to take that section apart....

I'd be very Interested to follow your progress on this if you have the time to post about it. I have been thinking of doing the same thing and started to draw something up in Fusion 360. My original 15 year old regulator has a pretty wide spread so have ordered a new one, but I am planning to throw a seal kit at the old reg to keep it as a spare.

[argus]

I gave it back to the student, and it was shooting about 3 inches higher. That seemed odd, but that could be from fixing leakage at the breech seals, although that seemed like a very big elevation difference. He re-zeroed, and shot a nice group. He took a break, and it was suddenly shooting very low....

From what I have read about these regs, my guess is that high pressure air is leaking into the low pressure section of the regulator. When you are shooting at a reasonable rate things seem more or less normal but when you leave it for a while the low pressure chamber is basically approaching cylinder pressure. The hammer spring then does not have enough force to open the firing valve fully against the high pressure so you get a weak shot. I think the likely culprit may be the tiny 1.5 x 1mm o-ring on the adjuster stem, and/or the delrin seal in the top of the piston. You could take measurements of the position of the stem before taking it apart so you can screw it down to the same position when putting it back together but to set it properly you would need the test guage, especially if you also have to dress the top of delrin seal in the piston to get it flat again. Very interested to see what you actually find.

[Gwhite]

I've got the pressure gauge, aluminum & a shop to make the tester. All I need is time...

Speaking of the little plastic seal on the front end of the piston: I assume they get chewed up a bit over time. Are those replaceable, or do you need to get the entire piston assembly?

I haven't found any place that sells the internal parts.

Thanks!

[brent375hh]

I've got the pressure gauge, aluminum & a shop to make the tester. All I need is time...

Speaking of the little plastic seal on the front end of the piston: I assume they get chewed up a bit over time. Are those replaceable, or do you need to get the entire piston assembly?

I haven't found any place that sells the internal parts.

Thanks!

The plastic seal is not replacable. It should be reusable, perhaps a light polish on 2000 grit.

When you write that you haven't found a place that sells the internal parts, have you called Pilkington? They have always had everything I needed, including a new piston to have just in case I needed one, and I didn't.

If you do need to get the end cap off because the inlet screw o-ring went bad, a soak of those threads in acetone greatly helps the cap to come off. Blue loctite will hold it in place after that. Measuring the current height of the cap will ensure it opens the valve at the same spot as before, but just slightly proud of flush also works for me.
Remembering where your inlet screw was positioned before contacting the inlet seat with the regulator assembled should get you back to where you need to be if you don't try to dress up the inlet seat on the piston.

[Gwhite]

Thanks!

Are the screw threads that may need Loctite the ones on the little front cap, or the adjustment screw? I bought a couple two-pin security screwdriver bits to take the caps off, but haven't tried that yet.

The air gun forum in England mentioned earlier has some photos where someone lightly refaced the seal on the piston. They said they didn't even have to change the shims under the Belleville washer stack, but I don't recall if they had to tweak the adjustment screw.

I haven't tried buying parts from Pilkington. It's good to know that they will sell them. Lots of repair shops are leery of selling parts, because it depletes their supplies, and cuts into their repair business. I suspect Neal Stepp would be another possible option.

[brent375hh]

The little front cap. It just needs a little fixative to stay in place as it contacts the cylinder pin valve. The regulator inlet screw has enough tension from its o-ring to stay put.

[Gwhite]

Got it! Thanks again.