Geissele SSA pins are 0.1550" dia 0.0001. Holes in the trigger can be 5 tenths over Geissele pin size. Kns pins are either .154 or .1555. So they are either too loose or just about a metal to metal fit in Geissele triggers

Geissele pins are chrome-moly steel that is rough turned, rough ground, heat treated and then centerless finish ground. They are a quality pin.

Why do we not recommend KNS pins? One is that they are the wrong size. Can the smaller diameter pins work? Yes, but they are not the intended size and there can be a 'softer" break to the 2nd stage with them.

But the biggest reason is that the KNS pins are soft. Sometimes when they are installed they pull up a burr that causes havoc with trigger operation. I get calls from frustrated customers where they are totally disappointed in their SSA because it either feels terrible or it hangs up. I spend all kinds of time on the phone wracking my brain trying to figure out what is going on and trying to work the customer through the problem. Finally, I ask the customer to send the trigger in (which I hate to inconvenience the customer with) and the issue is that the KNS pins are jamming the trigger up.

A hammer or trigger pin that rotates maybe 1/8 of a turn with each shot, *might* wear through the hard anodizing after a million rounds.

Let it rotate, it doesn't matter, its nothing to worry about. More FCG holes are damaged by people swapping the pins out every other week in an attempt to fix something that isnt broke, to get them to stop rotating.

Steve