PMI-I repair

[TarntKarntington]

I picked up a PMI-I (educated guess based on the helpful ID thread here) on ebay recently that needs some work. It seems to pressurize fine, but as soon as I pull the trigger it starts to leak and can't even get off the first shot.


Is this seal kit a good place to start? https://palmerspursuit.com/products/seal-kit-12-gram. Any upgrades I should look at picking up while I'm at it?


Thanks in advance! I'm still drinking from the firehose on this site but it's heartening to see so many people doing cool stuff with brass, I've been out of the loop for a long time...

[BrickHaus]

When it leaks, is it down the barrel, or near the 12ie itself? Sheridans pierce the 12ie on the first shot, so it sounds like yours isn't really holding pressure at this point. The 12 gram face seal is likely toast, but it may be the valve stem too.

Pps is a great place to start, for seals, and that IS the kit you want for a full rebuild short of bolt o rings. Be warned members have gotten bad seals from them out of the gate recently. So you you may have a similar expierence.

You should be fine to do so though.

Sheridans can have 2 valve types. Cartridge, and component. Pmi 1 is most likely component, which the kit you posted is the right kit for.

you can confirm by getting the back cap off and looking down the lower tube from the back. If you see a squared nut insert. Its a component valve.

You will need a valve tool to get the valve out.

You can easily make one if you have the tools, but you can likely order one with that seal kit to be sure you can get at those bad seals.

[TarntKarntington]

This is super helpful, thank you! Based on your description it does sound like it's not holding pressure, I only tried it once but I recall the leak being closer to the frame itself. I'll go ahead with that kit then and pick up a valve tool as well.

Dumb question: is 12ie just the cartridge?

[JeeperCreeper]

Yes 12ie, 12g cartridge, cart. They are called many things.

[XEMON]

Keep in mind the 12g face seal and valve cup seals are the same for components and cartridge valve.

[AnarchicArctic]

Best bet when acquiring used brass is assume it’s broken and do a full rebuild. Go through it, clean the valve, replace the seal and orings. Lightly oil and reassemble. Most of the time it should work fine after that. If not you can rule those out and look at the valve pin or the springs.

[TarntKarntington]

Good call! Somehow I've gotten lucky up to this point, before this I was 4/4 on used Sheridans. It helps that three of those were purchased 20 years ago I suppose.

[jeramiej]

If on first assembly, it is still leaking a little, try a second go with a 12ie. Sometimes just needs to settle in.

The o-rings nowadays are all over the place with thickness. I have tons, PPS, o-ring Monkey, Bacci, JCAirguns, Airsmith Airgun kits, Buma full kit and Nitrile full kit. The good news, is they are handy elsewhere, ATV carb rebuild, for example.


pierce pins are suspect when new as well. MCB fix of red Loctite was excellent.


The good news is these guns are easy to take apart and fairly simple to assemble. Some older ones a bit more of a pain, where lacking quick strip and threaded rods to bolt come into play.

[TarntKarntington]

Thanks everyone for your feedback and insight! I'll get some parts ordered and take a crack at it.

[TarntKarntington]

Got the valve rebuilt with the Palmer's kit (well, mostly a generic paintball o-ring kit) and it's shooting great now. Thanks again everyone!

The seal and o-rings on the valve had basically disintegrated, guess it was older than I thought.