Hot first shot... but it's not the regulator seat?

[kemikos]

OK, I have a classic 'Mag here. The first of every string of shots is seriously hot - for example, the first shot might be in the 320-350 fps range, and subsequent shots are around 240. The longer I wait between strings, the hotter the first shot is.

Classic symptoms of a bad reg seat, yes? Except that I've changed the seat twice, following the instructions in the classic reg seat thread at the top of the forum. I'm pretty well convinced that the seat isn't the problem.

So what else could it be? Any ideas?

Thanks for any advice you can pass on...

[BlackVCG]

Your reg. valve pin, the stainless piece attached to the spring might have a nick in it that isn't allowing it to seal properly. Also, make sure you're putting the reg. seat in the right way. It should snap in to the reg. housing. Also, pull out the brass piston and clean off the o-ring and the o-ring groove. Put some oil on it and test it out. Make sure th put some oil in your ASA to get all the internal components oiled first and then go test it at the chrono.