FWB 124 low power, and seal questions

October 11 2017 at 8:41 AM
Steve D  (Login sd5782)
YC

I have a pristine San Rafael vintage 124 serial 38XXX that I bought from the original owner in 2010. The factory seal went right away, so I put in a JM Old School kit. This was in my earlier learning stages. The piston seal was very snug. I fitted a new breech seal at the time also.

I never got much velocity: 740 with Exacts and 770 with Express. I have maybe 1000-2000 shots through it now. Currently 730 with AA Fields. I checked the breech seal with tissue, and put the factory one back in with the same results.

After seeing all the posts of folks getting 800+, I opened it back up today. Actually, the tight piston seal wore in nicely, and is now just "snug", but no more so than most of my other guns.

OK, here is the question: When looking into the receiver tube, the face does not appear to be flat. There appears to be a raised center "plateau" that is perhaps dime size. It seems that the piston seal bottoms out on this center part and the outer lip of the seal never hits bottom. Indeed, my seal only shows signs of wear in the center part, and seems as if the lip never bottoms out.

I did get a long metal piece to feel along the face of the receiver, and it does seem that the center part is raised perhaps .010"-.015". Is this how this gun is made? No 'F" marks on gun, just standard Beeman marks. It would seem like to me that I am having lost air volume at this spot, and perhaps machining the center face of the piston seal down a bit would be the cure. I know that currently "cup" style seals do exactly that.

 
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