AR-15 bolt carrier replacement

whatzhizname · Jul 2, 2010

Hi there,
Not much of an AR-15 guy, but I'm trying to help a friend who has one. He needs to get a replacement Bolt Carrier Group, and we've found some online (like here: <broken link removed> ) but don't know exactly what to look for. Any and all advice would be appreciated.
Thanks!

whatzhizname · Jul 2, 2010

Maxfield said:
The LMT you linked to you linked to is a great choice. Personally I would consider BCM's bcg (10 bucks more on the same site), but they are both top of the line and either will be a very good quality part.

Thanks. That helps a lot, since we're newbies at this.
I do notice some say "auto" and some "semi", but I'm guessing you can't use the "auto" BCGs in a semi AR?

Ding · Jul 2, 2010

ideally you want a MP marked,correctly hardened bolt group.pretty much any of the top sellers will have this.This will insure you have quality parts that have been done right.about 120-150 for a BCG is about average but some can be had for a few bucks cheaper.I wouldn't worry about a FA carrier set unless you want one,it is still semi either way.good luck.

ob1 · Jul 2, 2010

whatzhizname said:
Thanks. That helps a lot, since we're newbies at this.
I do notice some say "auto" and some "semi", but I'm guessing you can't use the "auto" BCGs in a semi AR?

Sometimes you can find a f/a carrier at a lower price than a semi, especially if you look around at gun shows.
You didn't mention the brand of your friends AR, but I assume it was purchased new and fully assembled as a semi. If not, you might want to verify that it is not a "parts gun" which has been assembled from surplus parts, some of which could also be f/a. If so, you could run into legal problems if too many of those parts are already in that gun, when you add a f/a carrier to the mix. (some of these could include the hammer, selector, disconnector, and trigger) If in doubt, have someone take a look at it or pass on the f/a carrier.

TonsOfOregonBrass · Jul 3, 2010

ob1 said:
Sometimes you can find a f/a carrier at a lower price than a semi, especially if you look around at gun shows.
You didn't mention the brand of your friends AR, but I assume it was purchased new and fully assembled as a semi. If not, you might want to verify that it is not a "parts gun" which has been assembled from surplus parts, some of which could also be f/a. If so, you could run into legal problems if too many of those parts are already in that gun, when you add a f/a carrier to the mix. (some of these could include the hammer, selector, disconnector, and trigger) If in doubt, have someone take a look at it or pass on the f/a carrier.

Unless the receiver has the third naughty hole for the auto sear a full auto BCG will not do anything. Even if all other full auto trigger parts are installed. And if there is a third hole then the gun is a machinegun even without the autosear installed so you are up S creek anyway. the Full auto BCG just weighs a little more. but there is no reason not to run one.

ob1 · Jul 3, 2010

TonsOfOregonBrass said:
Unless the receiver has the third naughty hole for the auto sear a full auto BCG will not do anything. Even if all other full auto trigger parts are installed. And if there is a third hole then the gun is a machinegun even without the autosear installed so you are up S creek anyway. the Full auto BCG just weighs a little more. but there is no reason not to run one.

You didn't mention the ATF habit of considering a weapon a machinegun if it has too many Full auto parts installed (regardless of whether it is capable of firing in full or not) The drop in auto-sear made it possible to.. " turn one on " without drilling the receiver.
My point remains, if you have just under the maximum allowed number of f/a parts installed, the introduction of a f/a carrier would put you into the felony violation category whether you are talking AR-15, M-1 carbine etc.

TonsOfOregonBrass · Jul 3, 2010

A standard AR15 will have to be milled out to accept the auto sear. a drop in auto sear can be a registered part on its own. so then you have a host. If you do not have a DIAS then the parts will not do anything. AR 15 Full auto parts are really not any different then the semi parts. the hammer and selector are the only things that are different. other then that eveything else is the same. the hammer without the auto sear will not do anything. the selector without the auto sear will not do anything. combined they will not do anything. you have to have an autosear whether it be drop in or installed. either way if you have either of those on an unregistered gun you are up S creek. if you dont have them, they you do not have a machine gun.

Lots of manufacturers sell guns with auto parts installed because they are not really any different then standard parts.

If you are not doing anything to make the gun go full auto then the ATF has no reason to look at you. if you are stiring the hornets nest then yes having the parts in there would be bad times. but as long as the gun only fires one round when you pull the trigger, and you are not modifying it. It would be damn near impossible to prove constructive intent. Now if you have a DIAS and the parts then yes you are going to be in trouble. But just an M16 bolt and a couple other parts cannot do anything.

Also what is the number of installed parts the ATF has determined to be too many. when i talk to them i havent been told anything about a magic number. also i cannot find any letters from the ATF or in the laws that mention anything about X number of parts = machine gun.

do you have any documents to back up the claim that you cannot have x number of parts. Cases i have seen, the people in trouble were trying to modify the guns to fire full auto. There are certain full auto parts you cannot have in the gun. like the auto sear from the AR, or the Auto Sear in an AK, or a slotted rail, or the third holes drilled. Not just a full auto bolt.

ob1 · Jul 3, 2010

Well, this seems to have the potential of a tennis match in another forum, which, if I had the time right now I would be pleased to oblige....for now, I'll leave you with these few. I will make an attempt to find you some of that data in my storage, could take a while.

1. An AR receiver must be milled to accept a drop-in. Yes and no, but mostly no...
Colt did voluntarily make a small change in their large hole receivers (H-bars) to make it necessary to file out the walls to accept a drop-in. but this is not true with many other models such as can be seen in the SP-1 AR models and many after market receivers,.... hence "drop-in". You must be dealing with an over-sized drop-in if you need to file, .....been there, seen it done with a registered drop-in (JCB auto sear) without any mods to the receiver whatsoever.

2. Hammer and selector the only different parts ?..NO WAY...You might want to lay an M-16 and an AR disconnector and trigger side by side, there is indeed a difference.

3. ATF regs. citations. Sorry but I dont go around collecting and saving these, for the chance that I might need to quote one for a thread. This being said, I am sure that with you being in the business you can agree that if there is an agency of the Federal Government that operates in the "gray zone" it is the ATF, this local jurisdiction most certainly included. The written ATF regs are vague in many places for their latitude, not for our benefit.
If, as you say we are talking about a "hornets nest", the hornets are out there and do consider "constructive possesion" prosecutable.
The fact is, you rarely see one of these cases go to trial due to the existence of other pending charges on the defendant. There is also the enormous legal expense to fight the charge compared to taking a plea bargain or probation and confiscation.

Off to scrub the grill........I'll jump back in later