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Chrome lined barrel question

1109 Views 36 Replies 15 Participants Last post by  IRON WORKER
Looking on the Criterion website it shows that chrome lined barrels are fully chambered while non-chrome barrels are short chambered. Is this true for USGI barrels also. In other words if I was to find a NOS USGI barrel which was chrome lined would it be fully chambered or short chambered?
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Chrome is hard, so reaming it would be a job requiring very expensive tooling. PLUS, once you nick scour or gouge chrome, especially at the end, or beginning, where chrome starts, you could, or as the country boys here say, "you might could", get flaking of the chrome, thus ruining the chamber and negating the advantage of having it chrome lined in the first place.

Jarhead
 

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Now, it is a different story with black nitrided barrels, right? I mean, if you use a carbide reamer to ream out the chamber it would destroy the nitriding in that section, but you wouldn't have flaking, correct?
 

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Now, it is a different story with black nitrided barrels, right? I mean, if you use a carbide reamer to ream out the chamber it would destroy the nitriding in that section, but you wouldn't have flaking, correct?
Correct. Nitride isn't a coating, it's a treatment of the metal.
 

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Chrome is hard, so reaming it would be a job requiring very expensive tooling. PLUS, once you nick scour or gouge chrome, especially at the end, or beginning, where chrome starts, you could, or as the country boys here say, "you might could", get flaking of the chrome, thus ruining the chamber and negating the advantage of having it chrome lined in the first place.

Jarhead
When the Army first introduced chromium plated chambers and bores there was question of what would happen if they had to ream out a chrome plated chamber. So, they tested it.

A carbide reamer is needed and best results were obtained with a pull-through type set-up. No flaking was observed when the chromium was deposited properly.

"Surface roughness readings showed headspaced, chromium plated chambers of fully plated barrels to be as smooth as the chambers of barrels plated in the bore only. Proof firing results of the barrels having chromium plated chambers were satisfactory.

"The length of tool life proved satisfactory particularly when oil is used on the reamer. At least 50 barrels per grind should be obtainable when the adjustable M1 reamer with carbide pads is used."


"Investigation of Chromium Plating Caliber .30 Barrel Bores and Chambers and Headspacing Caliber .30 Barrels having Chromium Plated Bores and Chambers," Springfield Armory, Dec 1957.
 

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Now, it is a different story with black nitrided barrels, right? I mean, if you use a carbide reamer to ream out the chamber it would destroy the nitriding in that section, but you wouldn't have flaking, correct?
Nitriding is a form of surface hardening, similar to carburizing, only you are infusing nitrogen atoms into the steel not carbon atoms.

If properly done chromium plating will adhere very well to the substrate. Adhesion between a chromium layer and the substrate metal is achieved by a molecular bond. Bond strengths in excess of 35,000 psi are common. Flaking is only an issue if the surface was not adequately cleaned.
 

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Remember you are working with commercial receivers and chrome lined barrels will not always (make that usually) head space properly. The military allowed reaming so I purchased a carbide reamer from PTG that allows me to ream chrome lined barrels. I also have a GI pull through reamer that works well. There have been no problems related to reaming chromed lined barrels.
 

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When the Army first introduced chromium plated chambers and bores there was question of what would happen if they had to ream out a chrome plated chamber. So, they tested it.

A carbide reamer is needed . No flaking was observed when the chromium was deposited properly.

"Surface roughness readings showed headspaced, chromium plated chambers of fully plated barrels to be as smooth as the chambers of barrels plated in the bore only. Proof firing results of the barrels having chromium plated chambers were satisfactory.

At least 50 barrels per grind should be obtainable when the adjustable M1 reamer with carbide pads is used."
Good research Brother lysander. Special tools needed: Check 50 barrels per tool life: Check Noflaking noted when chrome was "deposited properly"? What about when it not "deposited properly"?

Proof firing results...were "satisfactory". Not by today's standard.

All this on Taxpayer dollars, so who cares? Ammirite?

I respect yall, but I do not want my chrome-lined chambers to be altered, no matter who made them. Gettng the bolt to fit properly is the preferred method. It's enough to make a blessed body switch everything to nitrided barrels!

Jarhead
 

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Remember you are working with commercial receivers and chrome lined barrels will not always (make that usually) head space properly
Ted, in your experience, are the headspace values of USGI chrome lined barrels too short or too long - on average? Just curious if you have seen any patterns re this and commercial receivers?
 

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What about when it not "deposited properly"?
Depends on what the nature of the improper deposition. But, improper chrome plating should be cause for rejection, so it's a moot point.

Proof firing results...were "satisfactory". Not by today's standard.
On what evidence is this based on? How are today's standards different from the standards used back in 1957?

All this on Taxpayer dollars, so who cares? Ammirite?
Yes, it was done at public expense, as to who cares, anybody that needs to cut in to a chromium plated bore, be it a chamber to headspace it, or a hydraulic cylinder to repair it.

I respect yall, but I do not want my chrome-lined chambers to be altered, no matter who made them. Gettng the bolt to fit properly is the preferred method. It's enough to make a blessed body switch everything to nitrided barrels!

Jarhead
That's fine. But there are some receivers that are just to short . . .
 

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Depends on what the nature of the improper deposition. But, improper chrome plating should be cause for rejection, so it's a moot point.


On what evidence is this based on? How are today's standards different from the standards used back in 1957?


Yes, it was done at public expense, as to who cares, anybody that needs to cut in to a chromium plated bore, be it a chamber to headspace it, or a hydraulic cylinder to repair it.

That's fine. But there are some receivers that are just to short . . .
I thought the same thing, but the way it's stated, implies there is still some flaking of the chrome goin' on, my original comment/question.

Today's "standards", from what I see on the netwebs is, if you military-styled semi-auto ain't shootin' one hole groups, it aint' diddley.

Obviously the military does not need to worry about "taxpayer money" but J. Q Publik USUALLY does not have the funds for multiple barrel experiments. Also, I don't know what the proper tooling costs would be to grind the chamber, but you know the price has to be added to each job if a tool only last for (50) uses.

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It is curious to me... I have heard it said that "with today's standards you don't have to worry about finished barrels" and have heard "with modern commercial parts, you can expect that you'll need to do some reaming/take some barrel shoulder off, etc".

Who knows what to make of it; I certainly don't.
 

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Most of the chrome lined barrels I've installed on commercial receivers have exhibited short head space, Some were OK and a few have been too long. My preference is non-chromed barrels that are short chambered. Perfect head space and accuracy are always the goal. However, I have installed some chrome lined Criterion barrels that had accuracy as good as most of the Krieger barrels I've installed.
 

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Ted. Thanks for the follow-up info. I have a nice August 1968 SA USGI M14 barrel that I want to use on an SAI M1A receiver, but not sure if my local gunsmith buddy has a carbide reamer that would be required if the headspace is a little short…
 

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Most of the chrome lined barrels I've installed on commercial receivers have exhibited short head space, Some were OK and a few have been too long. My preference is non-chromed barrels that are short chambered. Perfect head space and accuracy are always the goal. However, I have installed some chrome lined Criterion barrels that had accuracy as good as most of the Krieger barrels I've installed.
Thanks. I assume this regarding short headspace is true both of chrome lines GI and commercial (e.g. criterion) barrels just the same?
 

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Most of the chrome lined barrels I've installed on commercial receivers have exhibited short head space, Some were OK and a few have been too long. My preference is non-chromed barrels that are short chambered. Perfect head space and accuracy are always the goal. However, I have installed some chrome lined Criterion barrels that had accuracy as good as most of the Krieger barrels I've installed.

My LRB came with a Criterion medium-weight chrome-lined barrel. 100 yds with Lithuanian ball. It's bedded and the gas cylinder is shimmed, but some of this is definitely the barrel. I will never sell it, and my nephew is on notice that I will come back and haunt him if he does...


Rectangle Circle Astronomical object Space Pattern
 

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This one reason I prefer stainless barrels that can be reamed and will be durable enough for the way I as a civilian with use them. I like stainless because of it resistance to rusting in my humid florida climate. One can also grind a bolt face if the chamber is not too far short chamber, but of course this is not ideal.
 
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