Air Arms Owners Club

Hi all. I'm tearing what little hair I have left out with this S410. It's a .22 carbine and very well used that my friend asked me to look at as it was leaking on the firing valve. I sorted that out but it was inconsistent so I gave it a full rebuild. It's now had a new firing valve and pin, both springs and all new o-rings. I just can't get the power back up to where it should be. It just won't go above 530fps with JSB's when it should be 580ish.

I phoned Julian last week and he said to clean everything which I've done. The hammer shaft is polished to a mirror finish and the hammer has almost zero friction but I'm lost for ldeas. Anyone got any suggestions please?

Jon

I'll have a look in a bit but I remember thinking that the hole in the back of the firing pot was too small. It's smaller than the transfer port so it's likely to be the problem.

Jon

What's the year ?

Ok, what did you set the firing valve at ?
Have you inadvertently blocked the transfer port when refitting the seal ?

Is the transfer o’ring still in place.

BBF

Leave the hole in the pot alone
And what pressure are you filling to when you chrono it ?

I took the hole in the pot out to 4.6mm and set it at 57mm protruding. Filled the reservoir to 150bar and still only making 530fps with JSB'S.

An update. I discovered that the hammer spring spacer (W263) was missing and I couldn't find it. I made one on the lathe and inserted it and it went up to 560ish. That's in the ball park but before I changed the firing valve it easily made the limit. The only simple thing that I can think of is that I don't have the correct transfer port o-ring and am using a set that I have which I think are too thick and may be covering the port when compressed.

Jon

S427 is the transfer port seal,
My S410 .22 is running at 565fps 11.36ftlb with AADF5.52 16gn
That's at about 130bar, well enough