M-16: When did chrome lining become standard?

[natedog]

When was chrome lining added to the chambers, bolts, bolt carriers, and barrels of M-16s? What commercial AR-15s have chrome lining? When was it added to commercial SP-1s?

 

[ny32182]

Chrome bores and chambers became standard on mil-spec rifles sometime after the start of the Vietnam war. On the early vietnam guns, the chrome was eliminated as a cost cutting measure, but was added back in when a combination of bad powder and intense humidity in the jungle resulted in fouling problems in the non-chromed weapons, and has been standard ever since. At least, that the internet rumor.

It is almost universally accepted that chrome carriers and bolts cause more problems than they fix, and I don't believe they were ever military-spec for any signifigant amount of time. They are brittle if not made correctly, and accellerate wear on the upper reciever.

As far as current production rifles go:

Bushmaster uses 4150 mil-spec steel and chrome lining in almost all their rifles (unless otherwise indicated).

RRA uses slightly weaker 4140 steel and offers one chromed model, to my knowledge.

Colt uses 4150 steel, but only chrome lines their MT6400 model, at the moment, afaik.

Other brands, I don't know about.

If I've given any incorrect info, someone make a note of it.

 

[rock jock]

It is almost universally accepted that chrome carriers and bolts cause more problems than they fix

Oh, I don't know about that. The newer hard chromed BCG's are supposedly much, much better and actually increase reliability.

 

[DMK]

Chrome bores and chambers became standard on mil-spec rifles sometime after the start of the Vietnam war.

Are you sure about that? It's my understanding that the barrels with chrome lined chambers were initially used to fix the problems, but barrels with chrome lined bores weren't used until later.

ttbadboy:
It is almost universally accepted that chrome carriers and bolts cause more problems than they fix, and I don't believe they were ever military-spec for any signifigant amount of time. They are brittle if not made correctly, and accellerate wear on the upper reciever

Rock Jock:
Oh, I don't know about that. The newer hard chromed BCG's are supposedly much, much better and actually increase reliability.

If I may add something here: Hard chroming of the outside of the carriers is not recommended due to hydrogen embrittlement issues. However, chrome *lined* carriers do not have such problems since so little area is actually hard chromed. I believe the chrome lining of carriers is current milspec, and is certainly used today by all the big names in ARs, but I don't know when it started. I think it was around the time that chrome chambers and bores were added, but don't know for sure.

 

[rock jock]

DMK,

I really am not familiar with the technical issues on chromed BCG's. I just know what I have read over at Ar-15.com about Young Manufacturing and Les Baer chromed BCg's and it is mostly very positive.

 

[DMK]

OK, here we go:

(May, 1967)
A chrome-plated chamber is approved for the M16 rifle family. A fully chromed bore will not be approved until later.

http://www.thegunzone.com/556dw-2.html

I really am not familiar with the technical issues on chromed BCG's. I just know what I have read over at Ar-15.com about Young Manufacturing and Les Baer chromed BCg's and it is mostly very positive.

You may indeed be correct. They may have fixed the problems and they may work OK. Either way, I believe Mr. Natedog is looking for info on standard equipment and aside from lower quantity makers such as Les Baer, I don't think that any of the major manufacturers use one and they aren't currently milspec.

 

[ny32182]

Are you sure about that? It's my understanding that the barrels with chrome lined chambers were initially used to fix the problems, but barrels with chrome lined bores weren't used until later.

No, I am not sure of the timing. I'm not sure if they added a chome chamber first, or a chrome bore first, or both at the same time... but I'm pretty sure that both were added after the start of the war, in one order or the other.

If I may add something here: Hard chroming of the outside of the carriers is not recommended due to hydrogen embrittlement issues. However, chrome *lined* carriers do not have such problems since so little area is actually hard chromed. I believe the chrome lining of carriers is current milspec, and is certainly used today by all the big names in ARs, but I don't know when it started. I think it was around the time that chrome chambers and bores were added, but don't know for sure.

This is what I was thinking. Yes, the INSIDE of the carriers are chromed, but when people say "chromed carrier", I think of a carrier that is chromed on the outside as well.

Chroming the outside of the carrier is something that has been available for a long time and is not mil-spec, so I have my own reservations about how much chroming the outside of the carrier really helps reliability... even if it is done right.

My next AR (mostly LMT) will have the LMT M16 carrier and LMT enhanced bolt. I doubt there is much out there that would be more reliable.

 

[Badger Arms]

Chrome Lined Bores were a Requirement of the TCC, IIRC, however they had already been implimented. I believe there was a transition period where the chambers and then bores were lined. Problem was, nobody knew how to do it effectively on such a small bore and the technology curve was a sharp one. Bolt carriers on Air Force AR-15's were Chrome Lined and replaced through attrition. There is no real need for chrome lining on the OUTSIDE of the carrier, but it does help cleaning up the inside of the bolt. It certainly helps with reliability to have a chrome lined chamber, and a chrome bore has certain advantages and disadvantages I won't go into. Don't have "The Black Rifle" in front of me, but it says in there about the time when it was adopted. I'm thinking 1966-1967, but I might be wrong.

 

[Daniel Watters]

As DMK noted, chromed lined chambers for the M16/M16A1 were approved in 1967. M16/M16A1 barrels with fully chromed bores entered production in 1971.