P17/22 transfer port o-ring falling out, how do you fix this?

[WobblyHand]

So I was shooting my P22 and I heard a muffled pop.  I looked at the muzzle and the pellet was just being held by the skirt!  When I looked for the o-ring, it was gone.  Eventually I found it (on the ground) and put it back in.  Yeah, I know, I should have gone back inside to get one.  A second try resulted in another pop.  This time the pellet stayed in the barrel and the o-ring was found on the exterior of the breech of the barrel!  Ok, time for another o-ring.  Put the o-ring back in, and shot the pellet out.  Back inside.

Found an 009.  It's a little thinner than the o-ring that was there before.  Stuck it in the end.  Tried a dry fire inside.  Upon cracking open the P22, the o-ring fell out.  Is there something I can use to keep the o-ring in there?

I was having fun with the P22.   It was shooting Excite Plinker Wadcutters fine (11.2gr).  A little high though, but I really hadn't sighted it in for 8m.  I then tried using the Daisy's 15.9gr, since I have a bunch of them.  Things were ok for maybe 10 shots.  Brought the pellets right in the bullseye zone.  After those 10 rounds, the o-ring trouble started.  It is quite hot here today, maybe 90F in the shade. 

[Earl]

Use a different 009 o-ring.
The note below is for the .177 but I assume the 009 will fit the .22 also.
Someone correct me if I am wrong.

"BREECH SEAL - The seal on the P17 breech is not the same size as the HW40 breech seal. They are very close but not the same. The P17 breech seal is slightly smaller. Thankfully the 009 works fine and actually gives me another 4 fps average velocity. The Chinese breech seal and valve plug seal seem to be the same size (both slightly smaller than 009). There is a Metric seal that measures M1.78x4.76mmID as compared to the Standard 009 that measures 1.78x5.28mmID (.208"IDx.070"CS)."

[WobblyHand]

Thanks, Earl.  It was a comedy of errors, actually. 

Apparently, the barrel moved away from the transfer port.  When I machined the barrel, I made a tiny trim ring that was sized for the correct spacing.  I placed the trim ring at the barrel/muzzle interface.  My barrel was made according to one of Wyoman's description.  In anycase, I could see there was a gap.  The barrel had shifted.  Fixed that.  Tightened down the little "wood screws" that hold down the barrel.  Also tightened the setscrew at the muzzle that I had put in.  My barrel was flopping about at the muzzle.  Much easier to group now!

Harbor Freight o-rings are undersized.  They are less than 1/16" in diameter.  Standard o-rings (at least what I found at McMaster) are 0.070" in diameter.  Doesn't matter, I found the o-ring set you had sent me (for a $5 donation to the GTA) and installed it.  Think I'll buy some spare o-rings.  009's are only $2.29/100 at McMaster Buna-N 70. 

So after I fixed everything, went back outside again.  Fired off some of the Daisy's.  They now smack the target, and the POI is higher than before.  It helps if you get rid of the gap!  The gap accounts for blowing the o-ring out and around the barrel.  My goodness, this P22 is fun!

BTW, I made the P22 based on a thread on GTA by Wyoman.  I used a 1322 barrel, rather than a 1377.  It's pretty easy to do.  Might dare to do a .177 with an LW barrel now.