Colt LE6920 Bolts and Bolt Carriers

jaycee

jaycee

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I haven't owned an AR for about 10-12 years, and had to do something about it. Last month I purchased a low mileage (500 rds) Colt LE6920 in the 8### range. I couldn't pass up a very reasonable deal on another one NIB in the 12### range. I've noticed a few differences in both bolts and carriers that I hope someone can enlighten me about:

1. Is there any "standard" method of marking that the bolt was MP tested? The bolt on 8### has a "C" marked on it by what appears to be an electric engraving pencil (lots of tiny dots). No "MP" - I thought all LE6920's came with MP tested bolts. Just for the nay-sayer's, I have no reason to believe that the original owner may have switched bolts. The bolt on 12### has a "MPC" marked on it, again with what appears to be an electic engraver. I did a web search of AR15 Bolts, and saw one that had "MPC" marked on it with what appeared to be a stamping. Make sense to anyone?

2. Both bolts are both void of any "underlug" for lack of a better description (the part that trips the full-auto sear as the bolt carrier comes forward). The Colt HB Sporter I owned years ago had the underlug, albeit shortened somewhat so it couldn't be used in a F/A. When did they start cuttimg up bolt carriers?

3. The bolt carrier on 12### has the area under the rear of the firing pin machined out of the hammer ramp (I believe that's what it's called), whereas 8### in intact. What gives here? Any reason for this?

4. Just out of curiosity, are AR bolts and bolt carriers all interchangeable?
ie. do the bolts have to be headspaced for each individual rifle, or are they all "within spec"?

Sorry if this got a little long winded.

jc
 
The "C" indicates that it is for commerical sale. MP and MPC mean magnetic particle inspected and proof tested. These are mil-spec bolts.

In 1993 Colt recieved a patent for their semi-auto bolt which has the entire auto sear trip area removed to prevent aftermarket conversion to automatic fire. This bolt is used in all semi-auto match series and semi-auto Law Enforcement Only rifles. It's basically to make the ATF and the anti-gun groups happy.
 
LE and recent civilain sale bolts carrier groups are just a cut M16 bolt carrier these days - you should notice that the lower rear is rough and not machined as nicely. BUT they ALL have the firing pin area shrowded. ALL Colt factory Bolts are MP'd - they should be marked MPC - It is engraved on to them not staped. The Bolt Carrier should have the Colt C stamp.

- IMHO as a Colt Factory cert'd Armorer -- you DO NOT have a LE6920 bolt carrier group in your most recent gun.
 
All new LE6920 in the US started to ship with a M-16 FA bolt for a number of months now , it just means your gun is in the contry for longer then that
 
Hindsite being 20/20, I probably should have waited until Monday to call Colt, but dammit, I couldn't wait!

I just got off the phone this morning with Colt's LE department; Colt didn't always mark it's MP'd bolts with "MPC". Many MP'd bolts were merely marked "C" - if it was a Mil-Spec gun, ie. a LE6920, it had an MP'd bolt, whether the bolt was marked with a "C" or an "MPC". Many 6920's were provided with bolts only marked with a "C", but as already mentioned, they are a "Mil Spec" firearm and the bolts were indeed MP'd. It wasn't until some of Colt's competitors started claiming that their non-MP'd bolts were Mil-Spec (which they weren't, because over and above the dimentions specified, the MP test was also required as per the original Mil-Spec), that Colt started engraving all their Mil-Spec bolts with "MPC". My 8### 6920 has a "C" marked bolt. My 12### 6920 has an "MPC" marked bolt.

As for the shrouding around the firing pin, Colt informed me that a year or two after the new millenium, there was a State Act (over and above the now defunct Assault Weapons Ban - probably Kalifornia) come into force that required that the firing pin shroud had to be milled out to differentiate the bolt carrier even further (in addition to the milled-off full-auto lug) from that of an M16. Apparently this Act was subsequently repealed, and this requirement "went away". The rep I spoke with couldn't remember which year they started shipping the "shrouded" bolt carriers again, but my 6920 ser.# 12### was from 2003 manufacture and definitely was from that time frame. My 8### 6920 was made prior to the above noted Act coming into force. Both of my bolt carriers are marked "C" by the way, and the gas keys are properly staked.

I have since received a PM from a fellow CGN member, who also happens to be the original owner of two 6920's - one in the 5### range, and another in the 10### range. Both of his bolts are marked "MPC", however, he has one of each bolt carrier as described above: the 5### has the full shroud under the firing pin and 10### has it milled away as on my 12###. Our friend also pointed out a very similar thread from ar15.com as a reference:

http:/www.ar15.com/forums/topic.html?b=3&f=118&t=258022

I hope this may clear things up a little.

If any other owner's of 6920's or 6921's read this post, please take a couple of minutes and look at your bolts and bolt carriers - I would really be interested to know how the bolt is marked and the carrier is machined, as would others, I believe.

jc
 
While we're on the subject on bolt carriers, does anybody here have any pictures on the differences between an M-16 carrier and a civilian AR carrier?
 
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