Worn sear + short on/off pin = shootdown?

[Hobbez]

ok, so, a quick run-down on the situation first. I built the wife a nice minimag and it was good, except..... It had horrible shootdown. You can shoot 1 bps all day with no problems, but soon as you tried to pop off a couple rapid fire, the second bloops out and the third drops at your feet. So, I did the usual: New o-rings all around, new bolt spring, good cleaning. no help. I got a little deeper: replaced the spring pack, valve pin, reg piston. no help. Noticed her new 45/45 had a low pressure reg, replaced it. no help. Finally, I replaced the pin in her on/off with the one out of my mag that I had put a RT on/off into. Now her gun works perfect. Shoots just as good as mine.

After all of that, my question is: Can a worn sear and a shortened on/off pin cause shootdown like I've experienced? Or can just a short pin have been the cause? I mean, my problem is solved, so it doesnt really matter. I'm just curious. Also, why would someone grind the end off of the on/off pin in a classic valve? Thanks in advance.

[athomas]

A worn sear and/or shortened pin should have caused rapid firing if anything. The only thing I can think of how a shortened pin would cause shootdown, is if the ground end had a burr that was slowing it down or if the pin was bent.

People would grind down the lower end of the pin to shorten it and alter the timing of the mag. If done correctly, it reduced the distance the pin needed to travel into the on-off oring before the sear tripped.