Wednesday, January 18, 2017

FWB 124 Replacement Piston Seal Quickie.

My friend Guy, who traded his FWB 124 to me years ago, managed to convince me to trade it back to him a while back. Recently he found it had no power and wasn’t pushing the pellet out of the barrel. We’ve covered FWB 124 disassembly already on the blog, but I thought the pictures of the damage and the replacement Maccari piston seal and spring warranted a quick post.
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At first I thought Guy had gotten sand in the gun, but it turned out that the piston seal had completely crumbled, so that even before I got the piston out little chunks were coming out with the spring.
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That’s a decomposed seal…glad it stopped shooting before it completely disintegrated.
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Had to chew up the old seal to get it out, compare it to the new Maccari seal.
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The new spring with spacers, compared to the old bent one. Good to replace it anyway. I didn’t do anything special, the piston seal was a little snug, but not tight so I didn’t machine or sand it. Lubed everything and put it back together. Fired 4 shots before it started to rain (Oregon winter), first one dieseled, but the last three were all 846 fps, which is amazingly steady. I’m sure it will continue to change over time as it all wears in.

8 comments:

Anonymous said...

Welcome back, Nick. We missed you!

Anonymous said...

Glad to see you back in action :-)
John-India.

Anonymous said...

So many of the sproingers from that time period had the piston seals disintegrate. A spring compressor is a must if you are to own these old gals, or at least have a friend who does.

RidgeRunner

69 Indian said...

Huge difference in the length of the old spring v.s. new. The surprising part is that the new spring is much shorter.

Anonymous said...

How is the cocking effort of the new spring compared to the old one??

Nick Carter said...

Way easier.

cubanfrog said...

Can someone please offer suggestions on how to remove the impacted piston seal material at the distal end of receiver (cylinder) ??
It's hard to comprehend how such a crumbled mess can adhere to metal so tenaciously!
Was tempted to use a long screwdriver to scrape it out but fear damaging the finish of the cylinder.
Any help on this would be greatly appreciated!

Nick Carter said...

I use aluminum or brass rod with the end cut at an angle to chip it out, then I use some steel wool held on the end of a rod (I use one of those drill flap sander holders, but there are a lot of ways to do it. And rotate it a bit with a hand drill. Basically whatever works. a little oil/WD helps loosen it. That stuff ends up being baked on from the high pressure/temp.