Quoted:
Doing my 1st (but not last) AR build. My only real problem has been getting the roll pins (Bolt Catch, Trigger Guard, and Forward Assist) fully seated without marring.
I'm using a roll pin starter to get it in, a brass punch to drive it the length, and then a small punch (1/32) to finish it with masking tape applied to the area around the roll pin hole.
The issue comes in getting it flush/slightly recessed without marring the receiver. Even with the tape, it's getting (very slightly) dinged up. Putting tape completely over the pin protects the area better but makes it hard to ensure that I hit the pin with the small punch and not the area beside it.
Any tips on how best to finish seating the roll pins?
Thanks.
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Ursus: In addition to the other suggestions about polishing, tapering and oiling the roll pins, the key to solving your problem is to use the right tools. There are two kinds of steel roll pin punches, and only two diameters specific to the AR-15's pins (see link below).
First you need starter punches, those with a little orfice in the end that the pin fits into. These hold the pin while you bang on it with your brass mallet. Second you need driver punches. These are not the same as ordinary drift punches, instead they have a little tit on the end to keep them centered on the roll pin. These make it much easier to put a layer of masking tape over the almost finished pin, then put the little tit into the hole in the pin and drive it that last millimeter past flush without marring the adjoining metal surface.
That's about it, a total of 4 punches for the AR, available from Brownells. BTW, the pin that affixes the trigger guard is special, you need to take care not to break off the fingers on the lower that the pin fits into. The c-clamp method described above is ideal since is doesn't place any undue impact stress on those little fingers. Good luck - CW
pin sizes