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WTK · New Member

Have a new Stoeger .177 X20 and I have now passed the 1K shot mark. Yesterday, I happened to look up the barrel (pointed at the sky) before inserting the next pellet, and was hardly able to see thru it until I blew thru it. This cleared it and all looked clean and shiny. After firing again, checked and found it full of smoke again??? A bit of smoke/fumes could be seen coming out of the chamber, but not obvious unless looking for it!
I was shooting JSB Staton 8.3 gr. pellets and clocked 4 at 877 - 889 FPS. Do I have a problem?

AirGunEric · Site Admin

Put some silicone oil through the transfer port to get in the chamber/on the piston seal- it will speed up getting rid of detonation immensely.

WTK · New Member

Thanks for quick response. Are you saying that this is still dieseling from the start? Will try the silicon oil.
After reading my message 3 times before posting, I still messed up on the pellet speeds - they should have been 777 - 789 fps, seems a bit slow.

AirGunEric · Site Admin

That output is low- should be closer to 900fps ('1200' is a marketing fabrication using 5gr pellets you can't buy anywhere).

robert w · Senior Member

probably done burnt the piston seal

WTK · New Member

Eric, are you thinking I might still be dieseling from the get go after this many rounds - would this be common (or not unheard of)?
Robert, yeah, it would seem that dieseling would cause higher rather than lower velocity, wouldn't it? Ya'll keep in mind that I am pretty new at this. For what it is worth, the accuracy seems to be about the same as before, not great but not all over the place - or getting worse. Piston seal - good excuse to try my hand at tuning. Will try some silicon oil first. Thanks guys.

WTK · New Member

P. S.
If this a piston seal problem, am I causing more damage by shooting? Should I try a bit of chamber oil first, or something else, or tear it down (or send it to someone qualified) and check it out?

Alstone · Moderator & Site Supporter

It look to me like a piston seal problem, and some lube is getting past the seal from the spring chamber, plus this would cause a low fpe as the seal would not be reaching it's full potential.

Al

AirGunEric · Site Admin

Lubing it with silicone oil to see what occurs won't hurt anything- even if the seal is damaged. It is possible a rifle would still be dieselling from the factory after 1000 shots- the amount of oil I've seen in some Chinese-made products is actually scary. However, this doesn't explain the lower power- so you probably do have a boogered seal at this point.

I don't know what the Stoeger cross-references to- they are all Chinese models. Based on the regular wood-stock X20, it's looking like the same builder as the Umarex/Ruger branded guns- i.e. BAM- but which models cross one another I can't say.

WTK · New Member

Thanks for the feedback guys. Shot another 3 rounds for speed late this afternoon (just before the sun quit on me), and still got 770 to 793 fps so I guess it didn't heal itself overnight. Guess I'll keep it together (shootable) till I get the Chamber Oil to try, then take her down to see what's inside. Meantime, I'll keep surfing to see which parts are available and where.
I'll be back!

Dukemeister · Member

Stoeger X20 is a fancied up Bam B18/19, so the stock piston seal from a Quest/Phantom/Trail/Optimus/Vantage/Summit will fit.

WTK · New Member

Haven't checked in in a couple of days, so Duke, thanks for the seal info.

WTK · New Member

Update for what it is worth. Tried the silicon oil (I think, it's hard to see what goes into the transfer port), didn't see any change. Went to the ARH site and ordered the Small Apex seal (for B19 and such). When I got it and took the gun apart, I found the seal measured about 1.020" OD while the cylinder measured about .985" ID (and the original seal was .990"). Didn't get any conformation that the new seal was REALLY too big, but I thought it must be so, I ordered another seal at .995" (for Gamo?).

I have now de-burred, cleaned, slicked up with Moly, Tarred the spring, reassembled, tweaked, scoped, and finally started shooting again.

Conclusion: It cocks much smoother and easier, the trigger is now at 13 oz and stable, barrel breaks easier, safety is smoother, and otherwise it shoots about the same? Got pretty good consistancy on velocity at 790fps and the accuracy is about the same (if slightly worse) as before. But it was a fun experience, and I'm sure I will do it again (also got a new Merlin spring while I was at it). Testing pellets again. After all settles down, I will test velocities again, then put the new spring in and do it again.

Bill

shawnhu · Member

Perhaps the problem is not in the seal, but the spring?

Basher · New Member

My stoeger x20 still smokes sometimes after ~2500 shots.

BTW I dont like my X20, its to inaccurate for hunting