New Seals For the Slavia 618, Part 2

With the Slavia disassembled, I took some measurements and tried my hand at making a piston seal. Those of you who read the blog know of my failures making a seal out of both Delrin and Teflon for the Predom Lucznik, this time I decided to try using some 80 durometer urethane rubber. 80 durometer is a little soft, I suspect, for a piston seal, but it's what I had on hand for my hydraulic die forming. I used a hole saw with the pilot removed to cut a plug from some sheet that was about 5/8" thick.

I chucked the plug up, drilled a hole through, then bored the recess.

I found this internal grooving tool in my drawer of misc. toolbits.

And I made the recess. The rubber didn't cut particularly well, but it did cut. If I had had some dry ice on hand I probably would have frozen the rubber first to make it easier to machine. But I didn't.

Hey, it snapped right on!

I mounted the plug on a mandrel and turned down the OD, finishing the last few thousandths with some 180 grit sandpaper.

I then parted it off to length.

I put the face groove in with an extremely sharp little tool I keep working on...

I then put the detent back in the barrel, and reassembled in reverse order. I lightly oiled the breech seal, which was somewhat rough.

I test fired the rifle. Before doing all the work it was shooting Crosman Premier Light pellets (7.9 grain) at 360 fps, although it was not a thorough test (I only shot a few through). After all this work it was spitting them out at an average of 312 fps. Not so good. I noticed that there was a light spray of oil on top of the breech. That hints at the fact that the breech seal may not be in the best shape.

So I found some leather and cut the OD for a new breech seal.

Then I carefully lined up a smaller punch for the OD. Then I made another one because the hole on the first one was off center.

I trimmed all the fuzz out of the center with an xacto knife.

The new seal in place, and oiled. I tested the rifle again and it was now shooting the CPL's at 394 fps. I was able to wring out better performance! Yay me!


I think I'll look for more Slavia airguns in the future. I have a 624 that was in very rough shape which I let the kids shoot, and the 631 I bought years ago at the flea market.