Hey Arfcom,

So I'm doing the KNS piston install on a PSA GF3. The factory pin which retains the piston is not welded, appears to just be an extremely tight press fit.

Here's the issue: I was able to get it to drift about 1/6 of the way out with a center punch, no drilling needed to get it started. But it's become immovable from there, no amount of strikes from a dead blow hammer + punch will move it any further.

Should I (carefully) just drill it out bit by bit to see if removing material will make it easier to drive loose? This is the most stubborn pin I've ever dealt with.

Get it in or on a solid fixture and use a heavier hammer before you start drilling.

I had it chucked up in a vice with nylon jaws squeezing the carrier and a nylon block supporting the piston stem. Dead blow is 24oz.

How heavy a hammer are we talking? I'm game to try whatever.

To close this out/in case it's helpful to anyone else down the road. I used a 3/32 cobalt bit and carefully removed material from the pin. Once about half of the pin was drilled out, the rest broke free with a punch and heavy ball peen hammer.

No damage to the carrier or factory piston and the KNS piston threaded in without resistance. Quite a bit of slop with the KNS roll pin but it's well undersized vs the factory pin and doesn't take any force, so I'm not worried about that.

Glad you got it fixed. I thought we were supposed to drill out existing pin about 1/4-1/2 way from both sides?  

I've only done one KNS install (M92 pistol) and the video I watched said to do this to give metal some place to move to as you hammer it out.

With the caveat that my AK knowledge is elementary, I think it falls under "it depends".

Some people have been able to just drive the sucker out like a normal roll pin on an AR. Others have to drill out a little bit. Others have to drill out the whole thing. Some are welded in place, some are peened over a bit then ground flush, etc.

Mine was not budging without being drilled out. A hydraulic press would have motivated it but I don't have one sitting around