Valve mod - pcp pistol

What a relief, I was starting to hate stainless.

The main thing with drilling stainless is high feed and lower speed.

It is not the heat that hardens stainless. Regular 304 and 316 are non heat-hardenable.

They only become softer with heat. But they work-harden very readily (316 moreso).

So applying too little pressure to the drill causes it to skim along the surface

without starting a chip. This work-hardens the surface you're trying to drill.

The problem with heat is that it blunts the cutting edge of the drill

which leads to work-hardening of the stainless, accelerating the issue.

HSS with cobalt can handle higher temperature.

I had been struggling trying to find a leak. At first I thought it was a line on the inside of the tube from production, so I honed it with 300 grit on a dowel in the lathe. It wasn't this, so I took a serious look at my O ring grooves and I had left a small ridge on the sealing side of it. removing this  seems to have done the job.

I reassembled the pistol and fired a shot over the chrony, and very interestingly it only read about 4 fpe. I figured this was due to it being too close because the next shot, from further away was better than I expected at a healthy 19.77 fpe. I still have to make the lockup device for the bolt/probe, so I am holding the probe in to fire. On the next shot I got 20.98 fpe.

 I have learnt that making sure there are no leaks in the transfer port area has a big impact on the power output and you can loose a lot of energy through leaks.

I had cut a tapered lead into the barrel and I need to get a slightly thicker probe O ring too as it gets blown out of it's groove, so once I get that and the lock up sorted I am likely to see over 20 fpe for this .25 cal  puppy.

I don't know how accurate it will be, but I am very happy with the results so far.  26.23 grn pellet @ 600 fps