I would like to know from any AR scholars whether they have any actual info, studies, and or test links to indicate that chrome carriers substantially accelerate receiver wear?

My question is prompted by a recent topic on this question, and I would like to know whether anti-chrome bias is: urban legend or lay opinion or informed opinion or fact.

It would seem to me that since chrome is smoother, has higher lubricity (it's slicker) and a lower coefficient of friction, it would LESSEN wear on the interior sliding surfaces of the upper receiver.

Fact supporting the hypothesis that chrome is harmful:  chrome surface hardness is significantly higher than the other metal surfaces of an AR receiver.

My answer, So what?  The carrier does not bang into anything other than the buffer. Who cares if the buffer gets banged up?  The buffer  isn't going to break or cease functioning.  Otherwise, the carrier just slides back and forth in the upper.  What damage can be caused by a slicker carrier sliding back and forth?

Is there any REAL (not imagined) detriment to using chrome carriers?

I think it's more than "urban legend or lay opinion or informed opinion", otherwise the U. S. Army would still be using them.

Oh, LTC Santose, where are you

[nitpick]The carrier actually contacts the hammer, forward assist assembly, bolt and cam pin. [/nitpick]

I can't imagine a chrome-plated carrier significantly shortening the lifetime of any other part... this sounds like it might be a problem dreamed up by folks who don't sell chromed bolt carriers.

Quoted: [nitpick]The carrier actually contacts the hammer, forward assist assembly, bolt and cam pin. [/nitpick] I can't imagine a chrome-plated carrier significantly shortening the lifetime of any other part... this sounds like it might be a problem dreamed up by folks who don't sell chromed bolt carriers.

Hmm yeah its such a non-problem that chrome lined carries ARE NOT deployable as combat weapons by the US Army (the worlds largest and oldest user of these kinds of rifles).  Chrome lined carriers can only be used on training rifles.  

If it were not a problem (and it was 'just' as cost issue) then the chrome lined carriers would be deployable.

From TM 9-1005-319-23&P (1 May 1991), page 3-17

NOTE There are bolts and bolt carriers on fielded rifles, some with chrome-plated exterior surface finishes and some with phosphate coating Both finishes are acceptable under certain operational requirements and or restrictions Phosphate-coated bolt carriers are required for divisional combat units Chrome plated bolt carriers are acceptable for divisional noncombat units and training center units. Chrome-plated and phosphate-coated bolt assemblies, bolt carrier assemblies, and repair parts for these assemblies may be intermixed In any combination, with the following exception: Phosphate-coated bolt carriers are required for all deployable and deploying units Chrome-plated bolt carriers are acceptable for nondeployable and training center units.

The Crane SPR uses a chrome bolt carrier, along with all of the Knight rifles.

themao

IIRC, on early chromed bolt carriers the chrome would flake off and those flecks hanging around would make a mess of things.

Quoted: Hmm yeah its such a non-problem that chrome lined carries ARE NOT deployable as combat weapons by the US Army (the worlds largest and oldest user of these kinds of rifles).  Chrome lined carriers can only be used on training rifles.   If it were not a problem (and it was 'just' as cost issue) then the chrome lined carriers would be deployable. From TM 9-1005-319-23&P (1 May 1991), page 3-17 NOTE There are bolts and bolt carriers on fielded rifles, some with chrome-plated exterior surface finishes and some with phosphate coating Both finishes are acceptable under certain operational requirements and or restrictions Phosphate-coated bolt carriers are required for divisional combat units Chrome plated bolt carriers are acceptable for divisional noncombat units and training center units. Chrome-plated and phosphate-coated bolt assemblies, bolt carrier assemblies, and repair parts for these assemblies may be intermixed In any combination, with the following exception: Phosphate-coated bolt carriers are required for all deployable and deploying units Chrome-plated bolt carriers are acceptable for nondeployable and training center units.

I still don't see what the *problem* is.  Just because they do it this way doesn't necessarily mean there is a technical problem with the chome plating wearing out other parts in the gun.  It could be any number of other things.  I would be a trifle hesitant about quoting from an 11-year old technical manual at any rate.

In fact, I'd think the gun would get shot more in training than in combat, so using a chrome-plated carrier there really would accelerate wear & tear on the rifle.  

Thanks for the replies, gents.

Forest, the fact that Chrome carriers and/or bolts are not used in deployable weapons is interesting, but it doesn't give a reason for limiting use to training rifles.  I wish someone could give us an actual reason from the DoD or the armed services.  I think the reason Chrome is not used is because it is more expensive.  Why not save a few bucks for almost identical performance?

It seems (to me) that training rifles would see more use than the deployed weapons.  That might argue for the superiority of chrome regarding wear and tear.

Thanks, MSTN, for mentioning that chrome is MUCH, MUCH, easier to clean.  I have found that my chrome bolt and carrier are a cinch to clean.  IMO, ease of cleaning is a HUGE PLUS for chrome.

Quoted: bolts are not used in deployable weapons is interesting, but it doesn't give a reason for limiting use to training rifles.  I wish someone could give us an actual reason from the DoD or the armed services.  I think the reason Chrome is not used is because it is more expensive.  Why not save a few bucks for almost identical performance?

Then why replace them when deploying - doesn't that just ADD to the cost!?

It seems (to me) that training rifles would see more use than the deployed weapons.  That might argue for the superiority of chrome regarding wear and tear.

Training rifles are expected to be abused and if they fail - it doesn't matter.  I remmber being on the range at Ft Dix for Basic they had a 'van' with 2 civilian armorers to fix (i.e. replace parts) of the training rifles.  Training units don't get as much money or the new toys like the units that actually may go into combat.  So they have to make do.

I'll propose they actually allow the training units to keep the chrome carrier to save on the training budget. Replacing an Upper is FAR cheaper than buying a new rifle.

Quoted: I would be a trifle hesitant about quoting from an 11-year old technical manual at any rate.

Considering until THIS year the 11-year old manual WAS the MOST CURRENT.  Oh BTW they kept the warning in the Current version too.  Must be important as they haven't made chromed carriers for what, 30 years for the Military?

In fact, I'd think the gun would get shot more in training than in combat, so using a chrome-plated carrier there really would accelerate wear & tear on the rifle.

But in COMBAT the rifle NEEDS to function - if it fails or wears out in Basic Training nobody dies.  Remember this lesson with Chromed Carriers was learned the hard way - IN WAR.

NAVY SNIPER RIFLE, THE MARK 11 MOD 0, ALL USE HARD CHROMED BOLT CARRIERS. THE NAVY'S "PMOD" PROGRAM CALLED FOR THE

No offense, but going to the Navy for advice on the operational/Technical use of the M16 is like going to the Army and asking about Mk48 torpedos.  Yes I know the Navy includes SEALs and Marines - but they still have far less time & experience & personnel on the equipment than the Army.

Quoted: Quoted: I would be a trifle hesitant about quoting from an 11-year old technical manual at any rate. Considering until THIS year the 11-year old manual WAS the MOST CURRENT.  Oh BTW they kept the warning in the Current version too.  Must be important as they haven't made chromed carriers for what, 30 years for the Military? In fact, I'd think the gun would get shot more in training than in combat, so using a chrome-plated carrier there really would accelerate wear & tear on the rifle. But in COMBAT the rifle NEEDS to function - if it fails or wears out in Basic Training nobody dies.  Remember this lesson with Chromed Carriers was learned the hard way - IN WAR. NAVY SNIPER RIFLE, THE MARK 11 MOD 0, ALL USE HARD CHROMED BOLT CARRIERS. THE NAVY'S "PMOD" PROGRAM CALLED FOR THE [/qutoe] No offense, but going to the Navy for advice on the operational/Technical use of the M16 is like going to the Army and asking about Mk48 torpedos.  Yes I know the Navy includes SEALs and Marines - but they still have far less time & experience & personnel on the equipment than the Army.

I'm not arguing those points... I guess the big question is still, "WHY don't they used chromed carriers?"  

From the Bushmaster website FAQ:

"Q. Does Bushmaster sell chrome bolts or bolt carriers? Is there any performance difference between chrome and regular bolts and bolt carriers?

A. There are several technical reasons not to use chrome bolts and carriers. Mil. spec. in the Viet Nam era required chroming the bolts and carriers to guard against rust and corrosion, but it was found that chroming caused problems. The hydrogen present in the chroming process was sufficient to create a condition called hydrogen embrittlement wherein the hydrogen would react with the highly hardened steel of the bolt and/or carrier - and make it susceptible to catastrophic breakage if a final stress relieving process was not correctly followed. Additionally, if the chroming process was not done correctly, the chrome could “flake” up from bolt or carrier surfaces and effectively gouge or scrape off the receiver's baked lubricant coating and subsequently gall on the aluminum surfaces inside the receiver. This condition could very quickly stop the rifle's firing cycle - all good reasons why the Mil. Spec. does not now call for chromed carriers or bolts."

I'm curious as well - I just ordered an upper w/chromed bolt and carrier assembly . . .

I have also read what 300th posted before, that the original's (M16)were chrome plated and suffered catastrophic failures in the field.  Hence, the current military specs for the carrier.  Of note, the inside of the carrier, where the bolt is, as well as the chamber and bore are chromed.  
Besides, don't think you'd want a bright shiny chrome plated part of your gun showing in the field if there were other people looking to shoot at you!!

So what about TiN (Titanium Nitride) plated bolts/carriers?  Does anyone have info re: the pros and cons of TiN?

OK, so my original theory that Chrome does not increase wear is essentially correct.  It isn't wear, it's flaking from crappy chrome jobs.

So, the real answer as to why the Army doesn't use Chrome carriers is because of flaking of the chrome (Bad) which can cause galling and stoppage (in the mid 1960's).

That shouldn't be a problem if you check and clean your rifle regularly.  It also makes me wonder who chromed the original Vietnam Era M-16s and whether they did a good job (nope).  It would seem to me that flaking is a result of bad workmanship (according to the post by 300thMIBde, if a final stress relieving process was not followed, you could have catastrophic breakage). The early ARs also had other problems.  Aren't the chrome carriers produced today better than those produced in 1965?

Conclusion: A well made chrome carrier/bolt properly maintained and checked will function just fine with no increase in wear, and no decrease in reliability.

Quoted: Conclusion: A well made chrome carrier/bolt properly maintained and checked will function just fine with no increase in wear, and no decrease in reliability.

Nor would it have any advantages other than aesthetics. Carriers are steel and receivers are aluminum. I doubt the aluminum cares whether the carrier is plated or not - it's still harder than aluminum. I say, if you want one, get one. As for me, I have found enough ways to waste money. I don't need another!

"A fool and his money are soon parted." Call me a fool then. I have a chromed carrier and bolt. I have noticed neither advantages nor disadvantages to it (In operation or wear).
     I guess I'm part Crow. I'm attracted to shiny things. And NEW things I find are particularly shiny...LOL

Hey, I have one too! Complete bolt and carrier. Never been in a gun yet though (I got it in a package deal/trade years ago). I may use it one of these days if I ever build one of those fancy match rifles with no port cover. It definately is PRETTY!


Edited to add: in my previous post, when I said I don't need more ways to waste money, I meant that since the chromes have no advantages, I would not likely go out and buy them for ALL my rifles.

I was a small arms repairer in the Army for 4 years during the mid 1980's. During this time we were still in the process of weeding out chrome bolt carriers from the combat units we supported. I was always told that the reason we were taking them out was (like major duh) THEY WERE TOO DAMN SHINY. That was it, and not hard to believe after getting gigged for having a small shiny corner on your "subdued" rank insignia. News flash -- the Army doesn't like shiny stuff, guys.

I never heard squat about or saw any evidence of embrittlement, catastrophic failures, or flaking. In fact, we used to crush the "unserviceable" chromed bolt carriers in a vise, hammer them up good, and toss them into the dumpster and I can tell you they were plenty tough. The only thing I saw was that the chrome would be worn at the ends of the "rails" from sliding back and forth on the harder anodizing.

Quoted: I was a small arms repairer in the Army for 4 years during the mid 1980's. During this time we were still in the process of weeding out chrome bolt carriers from the combat units we supported. I was always told that the reason we were taking them out was (like major duh) THEY WERE TOO DAMN SHINY. That was it, and not hard to believe after getting gigged for having a small shiny corner on your "subdued" rank insignia. News flash -- the Army doesn't like shiny stuff, guys. I never heard squat about or saw any evidence of embrittlement, catastrophic failures, or flaking. In fact, we used to crush the "unserviceable" chromed bolt carriers in a vise, hammer them up good, and toss them into the dumpster and I can tell you they were plenty tough. The only thing I saw was that the chrome would be worn at the ends of the "rails" from sliding back and forth on the harder anodizing.

I can't help but to agree. I was also thinking that if there is a functional reason to make a change to a TM the change normally states the nature of the reason for the change. You defiantly hit the nail on the head about the Armys distaste for things shiny (with the exception of things made from leather!!), if any body doesn't believe this just ask a buddy who was in about "cook whites", metal insignia that hasn't been "Em'nued", or even about what happens if you miss a single eye on your LBE while "Emnuing", Hell I once had to do fifty push-ups for not subduing the drain holes on my jungle boots.

Thanks Fuzzbean,

What you say makes a whole lotta sense.  It is good to hear from someone who has actual experience with the chrome carriers (and their robustness and quality).

I can see why grunts would not want shiny and reflective materials that would attract the enemy's attention.  However, I won't be engaging in combat any time soon, so I will continue to enjoy my shiny, easy cleaning carrier.

Quoted: I was always told that the reason we were taking them out was (like major duh) THEY WERE TOO DAMN SHINY. That was it,

Uhh I hate to point out if Shiney were the reason - they wouldn't have bought them in the first place.

People seem to forget the lessons of war too quickly.  There were problems in Vietnam with them that did cause galling and problems.

Now I'll bet alot of it was due to "mass production for war" and poor quality control.  If that is the case then a properly chromed carrier (w/o hydrogen embrittlement) might be a good thing.

However I'd like to point out one AR15.COMer, who was posting last year he had cracked 2 of the DPMS chromed bolts in his AR and was buying a 3rd.  It would seem DPMS isn't doing it right and hydrogen embrittlement is a problem with them, even w/o mass war time production.

Quoted: Uhh I hate to point out if Shiney were the reason - they wouldn't have bought them in the first place.

I don't claim to be a big AR-15 historian, but it seems to me the gist of the story was that the Army as a whole did not want to buy the M16 AT ALL and it was shoved down their throats largely "as is" by President Kennedy's nerdy Secretary of Defense. In other words, it was never developed by the Army or to meet exact Army specifications, but was presented to them as a more-or-less "perfected" design. I suspect it took the Army some time to weed out a few features that ArmaLite or Colt or Kennedy's pocket protector boys thought a military rifle should have, and replace them with features that the Army thought a military rifle should have. Especially during the urgency and confusion of war.

I'm surprised to hear of the DPMS carriers failing, since the bolt carrier is not all that highly stressed. Except for around the cam pin slot and maybe the thinner areas under the bolt hole, most of it is just "there." Any failures that did or do happen might have more to do with excessive casehardening depth than with chrome plating.

If chrome was a significant problem when done correctly or a significant problem to do correctly, I would not think Uncle Sam would have been buying chrome lined M1911A1 barrels at the exact same time chrome bolt carriers where being phased out. Those barrels look mighty thin-walled to contain 20,000+ PSI in any case, not to mention the banging around they get externally as the weapon functions.