Valve mod - pcp pistol

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

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.

What a relief, I was starting to hate stainless.

I got RTD metal cutting compound. Its a paste that sticks to the bit as opposed to flooding it.