So to begin, I had a P2000SK which would not run suppressed with my Gemtech GM-45 no matter what grain. Failure to feed, stove piping etc. The usual litany of issues when suppressing a pistol.

I tried the GM-45 on my Glock 17 Gen 5 with various ammo. It wouldn't cycle etc with lighter ammo. With the 147 it did pretty well, better with some brands than others.  Meanwhile, my Osprey works with everything. I was beginning to be SURE the can was to blame. It was at this point I was thinking the GM-45 just didn't do well with weaker rounds, ie 9mm (I have a 10mm)

Gemtech said it could be the Lone/alpha wolf barrel I had.  I got a Glock FACTORY barrel.  Same results, if not even more picky with the 147 grain.

One day I went to the range with my HK P30SK, Glock 17L, Osprey 40 and GM-45. Here's the kicker, both guns functioned flawlessly with BOTH CANS!  I had ONE F2F with one of the two pistols on the GM-45 then, between the two guns I put over 150 rounds down range while swapping cans trying to create a malfunction. Never happened.  Basically, I created a situation I THOUGHT I WAS GUARANTEED TO RESULT IN FAILURE and yet my pistol functioned. Obviously the G17 has a poorly chosen recoil spring and that needs to be addressed.  Obviously I could just replace the recoil spring but my dilemma is, will it run as well unsuppressed?  I'd rather not alter a gun if I don't have to.

Considering you are altering the gun with replacement of a major component ( the barrel) I cannot see why tuning the springs for optimal function should be an issue at all.

My only issue is that, having altered the barrel, the gun functions without the can just fine with the threaded barrel.  When I change the spring, I fear making the gun without a can less reliable.  If my gun is only going to function well one way, I'd rather it work as advertised unsuppressed than suppressed VS tune the gun for a can then have it choke on weak ammo where a normal 17 will run no matter what.

Piston issue?