I was talking with the local gunsmith and was told that not only does the back of the carrier have to be modified so that it does not trip an auto sear, but the metal around the firing pin must also be removed. He says that the purpose of the metal being cut away is to expose the firing pin collar to prevent full auto fire. He also told me that a notch must also be made on the hammer itself to engage the exposed collar on the firing pin. He said I was misinformed about just removing the bottom back of the carrier to prevent tripping an auto sear and that if the full modification is not done, the carrier is illegal. I told him I thought the only reason the collar was exposed on the AR carrier is to prevent a run away weapon if the diconnector failed. He still insists unless the full modification is done the carrier is illegal. Can anyone help clear this up?

While your local gunsmith is correct that those modifications are what Colt [b]chose[/b] to do to the M16 parts for their semi-auto commercial offerings, he's incorrect that modified M16 parts are illegal unless they conform to the semi-auto specs.

All that is necessary to do to M16 parts [b]legally[/b] for converting them to semi configuration is to make them incapable of working in the full auto firing cycle.

This involves grinding the sear hook off the hammer, the tail off the disconnector, closing the back of the trigger, and grinding the sear trip surface of the semi carrier back enough that it won't trip an auto sear.

The selector is usually just replaced, but could be welded up so that the 'auto' position is just another 'semi' position.

The auto sear is not used and can't be installed in a semi receiver, of course.

luckdogonfire...The gunsmith you sited has some knowledge but it ain't gonna doo him no good until he addresses his ignorance problem. You were discussing putting a modified BC into an AR15...correct? Sounds like he was fixing to turn an orange into a watermelon...how the hell did ya graduate to full-auto demill from a simple BC question? As Circuits pointed-out...what sear would you be trippin' in an AR? There's the sear on the trigger for the hammer...but thats it, eh :o) Take a bolt carrier that was made for an M16 or variant, grind 5/8"-3/4" off of the butt-end...guaranteed, it will no longer function as a full tilt carrier. Put in an AR15 and you're set...legal too. Removing the metal shroud around the firing pin well isn't necessary, it just depends on what FP you have and the manf'r of your fire control group. get yourself a BC, hogg some metal out of it, put it in your rifle and see if it goes..click, clunk or BOOM :o) All Good...Bud

I put this question here because I had mentioned to the guy about the TAPCO kit I got last year. I told him that I used the M16 carrier, which is when he got into the legality of having it in the weapon. I told him that the rear of the carrier was modified and thats when he told me that it was still not legal. He had me worried about the legality of the weapon and I just wanted to make sure that all I needed to do was just the rear. I do not want to have any legal problems. I thank you for your answers  

ldof...You are welcome. Bigger considerations with the kits from Tapco, FAC, Sarco & Century are headspace & throat errosion. Sell the TriBurst parts and use the money for a new lower parts kit. Cut your BC and/or trade it for a semi-auto BC. Put it together & whammo...you're done. If you have a postban rifle you're going to have more work to do but if you're preban...grrrreat, go get'm. That gunsmith sounds like an anxious man...bet he's got an ulcer or two, probably drives his wife nutz! Thx...Bud