They are an oddball cross section. Not the common size of 1mm, rather 0.8mm instead. M0.8x8I could not find them on McMaster or Amazon. Theoringstore has a small selection of M0.8 in Buna-N 70D but not this particular size.I tried the M1x8 size and they would not fit. The way I remedied it was to load the O-ring onto a shank and insert it into my drill press, then use a Dremel with a rubber polishing wheel to carefully abrade down the OD.I know it sounds crazy but being able to shape an O-ring has gotten me out of a bind many, many times.
I just use a transfer punch as a shank to hold the O-ring. Or you can slip it onto the smooth end of a drill bit.To get a feel for it, my suggestion would be to experiment first with a thicker O-ring...one that will stretch and hug tight to the shank to help prevent it from slipping when the rotating polishing wheel touches it. Bring the wheel in slowly and give the O-ring a very light touch, otherwise it will try to squirt away. The smaller the O-ring's cross section, the lighter the touch required. Fortunately in this case you're only removing the tiniest bit of material so it won't take much. If you struggle with supporting the O-ring, use an emery wheel to grind a shallow groove in the shank.Oh and it may go without saying but don't just abrade a flat on the OD. You want to finish up by hitting the edges lightly to round them over so the O-ring won't snag as you push the barrel into the receiver.Lastly, I don't know how consistent SPA is with their machining tolerances over the long haul but on both my CR600W and CP1-M, the barrel was nearly a slip fit to the receiver. Meaning the O-ring is responsible for sealing only the slightest gap and the 0.8mm-thick OEM O-rings were a super tight fit. If you have to abrade yours down to 0.7mm or something like that in order to keep them from getting sheared off on installation, I wouldn't hesitate for a moment to go with it.
I bought a refurbished chaser kit from PA not long ago to tinker with and maybe mod it a bit as I'm still fairly new to the game. works fairly well in pistol form but after looking at the rifle barrel it seems the outer barrel o rings are fairly chewed up..Now I need a bit of help finding spares. I believe I got the measurements down to 1mmx8mm from the o ring store but not sure the material or hardness, is it possible for someone to confirm or correct me? Also I was wondering if anyone had any info on opening up the transfer port, I Googled around and didn't find much even with the other rebrands.
I just turned the barrel and opened the grooves slightly to fit the 8x1 oring, lube good and she fits tight.
Quote from: Firewalker on September 24, 2022, 12:28:33 AMI just turned the barrel and opened the grooves slightly to fit the 8x1 oring, lube good and she fits tight.That makes a lot more sense than chasing the odd sized rings.... the sad truth is that some of us don't have the ability to do that since we are lacking the tools.