[metallicafatcat]

Slam firing is only really solvable with a 90 degree mech or a lighter spring, or some fancy metal work. It sounds like the spring in the KS mags are too powerful or there is a flaw with the feed lips in general, which wouldn't be surprising.

 

[metallicafatcat]

You'd need a 90 degree mech to rid it completely. Look for signs of wear on the piston and piston sear.

 

[metallicafatcat]

You can't buy a 90 degree sear set. Different mechanisms.