I am installing a Geissele Match 2 stage adjustable trigger and am finding the trigger pin rotates.  The hammer pin seems to stay put, despite both pins being loose fits in the receiver (including the oversize pin included with the trigger).  The Geissele pins are proprietary and it is highly recommended to stick with these.  Bill Geissele sent me some extra large pins, but these are so large, they actually will not fit through the disconnector, although they are barely snug in the receiver.  Will the rotation hurt anything, or are the receiver holes just so big, I will have to get another receiver, or continue one other thing I tried.  I placed a ball bearing against the inside of the trigger pin hole, placed a spare pin through the opposite side hole, and then give the pin a firm hit.  The pin pushes the ball bearing into the hole, swelling the inside diameter in a concentric fashion.  Did this on both sides.  This helped, but do not want to hit it anymore.  

Ideas?

- Phil

Trigger pins rotate - don't worry about it.

Get a set of the KNS anti rotation pins.

KNS pins are specifically NOT recommended by Geissele, according to various sources.  The pin grooves are not in the same location as standard or KNS pins.  

I spoke to Bill Geissele and learned some interesting things.

1)  Oversize pins are identified by a thin barely seen groove adjacent to the two larger grooves at one end of the pin.  These are oversize HAMMER pins only, and are not to be used as trigger pins.  See #2.  They probably will not fit through the disconnector.  Mine would not.
3)  It is OK for the trigger pin to rotate in the receiver.  The pins are hardened steel with a micro finish, and will not abrade the receiver.  Some burnishing may take place, but once that happens, little more will happen.  Parkerized pins can be a problem (typical in LPKs), as their surface finish can hold abrasive material and abrade away at the receiver surface.
4)  As above, it is also OK for the hammer pin to rotate, for the reasons stated above.  But, due to load, better if that pin did not rotate.  This is why there are oversize pins just for the hammer only.  Still, rotation is not a big deal.
5)  The trigger and hammer pins both have two grooves each, at one end, although the trigger and hammer each use only one of those two grooves.  The trigger pin outside groove is where a leg of the hammer spring rests, thereby preventing the trigger pin from walking sideways.  The hammer pin bore has a circlip on the left side, which snaps into the inside groove of the pin, thereby preventing the hammer pin from walking sideways.  This is why the pin must have the grooves on left side (bolt release side).  
6)  The dual grooves for each pin were done for manufacturing expediency.  Manufacturing one pin that can do double duty is less costly than manufacturing two dedicated pins, one for the trigger, and one for the hammer.  

- Phil

Phil3
  I know the over sized pins are tight but it seems you'll have to step up to them.  They must be driven in.  Are these larger the the extra over size pin that came with the FCG?  Contact GSA again

 Ideally the pins should not rotate,  the trigger and hammer should rotate around them.   Any rotation will cause wear.

 Most of mine will rotate the hammer pin, non of the trigger pins do.
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I am using the oversize hammer pin for the hammer...I have no problem with that.  That oversize pin is still a somewhat loose fit in the receiver, but thankfully, it does not seem to turn when the hammer moves.  Bill Geissele specifically told me the oversize pins will not fit through the disconnector.  I tried, he's right, they won't.  Even if you could cram it through there, it would be so tight, the pin would surely turn in the receiver and not the disconnector.  Mr. Geissele also said these pins will not cause receiver wear.  They ARE very slick, and nothing like the pins out of a LPK.  It is interesting that my trigger pin turns, but not the hammer pin, the opposite of what you have going on.  

The additional hammer pins I got are somewhat larger than the one oversize one that came with the FCG.  It is still loose in the receiver.  The receiver holes are apparently relatively huge.  You should see how loose the LPK pins are.  

- Phil

Well, you got the info from the man.

 Don't worry about it and enjoy.  Some pins rotate, some don't.  
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