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Retcop

Chrome vs. Nitriding: Consensus Reached ?

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Is their a general consensus in the industry that there is not enough difference to matter between the durability and corrosion resistance between chrome lining a barrel and nitriding a 4150 chrome moly steel barrel  ?  I have not been able to find any published Military test results comparing the 2 methods. 

 

This also leaves us with chrome lining a bolt or chamber as compared to nitriding. I still see nitrided quality barrels being offered with chromed bolts and chambers.

Not sure why unless it is about saving money vs what is best, which is the entire crux of the biscuit.  

 

I know many who own an AR for possible social intercource will always reject nitriding because it is not mil-spec. I get that.However, when POF starts releasing rifles with nirided barells, it makes me take notice. But do we have enough data points testing both methods to make an informed decision regarding how nitriding compares to the performance of chrome lining the barrel for hard or "combat"  use  ?  Plus we should not ignore treatment of the bolt/BCG and chamber. 

 

Please discuss. 

Thanks.

John

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(I’ll let others who know more about AR’s talk about rifles.)

in shotguns, however, there is a lot of concern about moly/chrome barrels and steel shot. Steel, obviously, doesn’t deform like lead or bismuth. Steel shot “jams” up in the much harder moly/chrome barrels. Standard steel barrels tend to flex ever so slightly allowing steel shot to pass (sometimes ruining the barrel- but leaving the shooter’s face intact). Moly/chrome barrels don’t flex, causing a plugged barrel type situation including blown barrels, ruptured chambers, etc.

 

So, rigidity must also be part of the discussion for rifles?

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11 minutes ago, srjdsmith said:

(I’ll let others who know more about AR’s talk about rifles.)

in shotguns, however, there is a lot of concern about moly/chrome barrels and steel shot. Steel, obviously, doesn’t deform like lead or bismuth. Steel shot “jams” up in the much harder moly/chrome barrels. Standard steel barrels tend to flex ever so slightly allowing steel shot to pass (sometimes ruining the barrel- but leaving the shooter’s face intact). Moly/chrome barrels don’t flex, causing a plugged barrel type situation including blown barrels, ruptured chambers, etc.

 

So, rigidity must also be part of the discussion for rifles?

 

I have yet to see the issues of barrel harmonics, or brittleness or barrel rigidity brought up in the context of different barrel treatments on AR barrels. 

Steel shot and shotguns never entered my mind. 

 

The steel itself seems to make a difference, but I think we've long past using poor quality steel for bbls in the USA. Forming, machining, and rifling them is an entirely different matter. Correct me if you think I am wrong. I have no intention of buying subpar or foreign AR bbls from questionable sources.

Is the difference between 4140 CMV and 4150 CMV when chrome lined or nitride make a significant difference ? I'm thinking not, even though my man/gun brain 

tells me to buy 4150 for my "go to" rifles, if someone shows me it really counts.  My M1A has a SS barrel, and I am thinking about having it nitrided, although I did pick up on a single article that said nitriding does not always play well with stainless steel. I've seen manufacturers offer it left and right,  so who knows ? It's hard to find facts.  

 

I saw a 10.5 inch AR pistol BBL offered by RTBA for $ 32.50 ! !   WTH ? That takes more time and research than when there were less bbl makers,

and my reflex reaction is to pass right on by it because it is TOO cheap. That is part of the dilemma and extra dillegence needed as prices come down across the board

to avoid cheap crap .  IMO there is a difference between cheap and affordable. 

Cheap does not work right or is going to fail prematurely.

Affordable does the job at a more reasonable price.

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I try to not read the "experts" opinions on this and other matters. I have both. Waste anywhere between 300-600 rounds monthly. All is well. Too damn hot to "waste" any at the moment. :laugh:

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Posted (edited)

Nitriding isn't a coating. Chrome was in barrels for military weapons with the giggle switch to keep the wear down. Nitriding actually hardens the metal as it is a form of case hardening. Nitride will wear  slower. I remember reading an article where a guy had 11,000 rounds in his nitride barrel. He had some wear in the barrel at the lead-in from the chamber to the rifling but the rifling was still sharp when viewed through a borescope. I have no problem with regular non lined barrels as they are just semi-auto and are not fired every day.

Edited by gshayd
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Either will work for most usage. The nitride may shoot a tad better accuracy wise but not always. Pretty much you get the chamber with the coating or treatment. Either makes it hard on tooling if it needs clean up.  You'll never wear either one out period as a civilian . Even the hard charger hobbyists can't do it and I've met a few of those that as long as the goal is SD and not BR group shooting either will never have issues IMHO.

 

BCG's should be chrome LINED internally.  Externally it's what ever you like. Some guys have had poor quality chrome peel on the BCG exterior. I have a more than a couple that I have no issues with. Of course these are coming from people like Young currently. My first one was from OLY and it has never disappointed me in over 25 years of good usage.  I like the new boron stuff as it is easy to clean. 

 

Bullets going through a rifle barrel in slow mo make it look like a snake purging as they bulge out.  No rifle barrel suffers from the effects of it and they ALL do it. IIRC 4140 is cheaper than 4150 and a bit easier to machine.  Most upper tier tubes will be 4150 or 416R stainless.

 

Greg

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On 7/22/2019 at 1:39 PM, GLShooter said:

Either will work for most usage. The nitride may shoot a tad better accuracy wise but not always. Pretty much you get the chamber with the coating or treatment. Either makes it hard on tooling if it needs clean up.  You'll never wear either one out period as a civilian . Even the hard charger hobbyists can't do it and I've met a few of those that as long as the goal is SD and not BR group shooting either will never have issues IMHO.

 

BCG's should be chrome LINED internally.  Externally it's what ever you like. Some guys have had poor quality chrome peel on the BCG exterior. I have a more than a couple that I have no issues with. Of course these are coming from people like Young currently. My first one was from OLY and it has never disappointed me in over 25 years of good usage.  I like the new boron stuff as it is easy to clean. 

 

Bullets going through a rifle barrel in slow mo make it look like a snake purging as they bulge out.  No rifle barrel suffers from the effects of it and they ALL do it. IIRC 4140 is cheaper than 4150 and a bit easier to machine.  Most upper tier tubes will be 4150 or 416R stainless.

 

Greg

 

Please tell me why chrome lined BCGs are preferable to a BCG nitride inside and out ?  

Is it lubricity ?

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4 hours ago, Retcop said:

 

Please tell me why chrome lined BCGs are preferable to a BCG nitride inside and out ?  

Is it lubricity ?

 

 

Cleaning????

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5 hours ago, Retcop said:

 

Please tell me why chrome lined BCGs are preferable to a BCG nitride inside and out ?  

Is it lubricity ?

 

Milpec is chrome LINED. I suspect it gives a better seal and might be a tad slicker when you oil it up.  On the outside I figure cleaning is about the same. I only buy the chrome lined BCG's personally. 

 

Greg

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On 8/15/2019 at 2:08 PM, Retcop said:

 

Please tell me why chrome lined BCGs are preferable to a BCG nitride inside and out ?  

Is it lubricity ?

I'll take a stab at this one.  In the tooling industry, specifically injection molding, if you have two sliding members that you don't want to gall or wear, you need at least 7 points of hardness difference on the Rockwell C scale.  I'm sure there are other recommendations for different types of materials, but for the hardness we are working with here, I would assume this would be the case.  The hardness of the nitriding is dependent somewhat on the base material.  

If I remember correctly, hard chrome is around 62 Rc.  I expect that the gas rings are a bit softer than that and they just wear better when in contact with chrome.  It does wear in a little as the gun cycles.

 

You can take two really hard pieces of steel that are nearly the same hardness and if they are sliding against each other, they too will wear prematurely.  It doesn't really matter how hard they are, they just need to be different.  

Nitriding may work fine but chrome is time tested and well proven.  

I know that doesn't really answer the question, but it is something to consider.  

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1 hour ago, Winkel said:

I'll take a stab at this one.  In the tooling industry, specifically injection molding, if you have two sliding members that you don't want to gall or wear, you need at least 7 points of hardness difference on the Rockwell C scale.  I'm sure there are other recommendations for different types of materials, but for the hardness we are working with here, I would assume this would be the case.  The hardness of the nitriding is dependent somewhat on the base material.  

If I remember correctly, hard chrome is around 62 Rc.  I expect that the gas rings are a bit softer than that and they just wear better when in contact with chrome.  It does wear in a little as the gun cycles.

 

You can take two really hard pieces of steel that are nearly the same hardness and if they are sliding against each other, they too will wear prematurely.  It doesn't really matter how hard they are, they just need to be different.  

Nitriding may work fine but chrome is time tested and well proven.  

I know that doesn't really answer the question, but it is something to consider.  

 

That makes perfect sense.  Thank you.

What a brain trust we have here !   

The more I learn the more I realize what I don't know about metallurgy and the mechanical engineering factors that go into weapon design and materials.

John

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Only thing is, the M16A1, M16A2, M4 and all military issues variants are not chrome lined, they stopped using chrome BCG's and chromed lined BCG in the 60's if I remember right and just the chamber and barrels are chrome lined to prolong barrel life......

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5 hours ago, Rampy said:

Only thing is, the M16A1, M16A2, M4 and all military issues variants are not chrome lined, they stopped using chrome BCG's and chromed lined BCG in the 60's if I remember right and just the chamber and barrels are chrome lined to prolong barrel life......

 

That is interesting. I'd never heard that. Every mil spec BCG I've seen and all that I can find on the internet that  claim mil spec are all chrome lined. Could you find me a source on that one Rampy? It would be appreciated.

 

Greg

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2 hours ago, GLShooter said:

 

That is interesting. I'd never heard that. Every mil spec BCG I've seen and all that I can find on the internet that  claim mil spec are all chrome lined. Could you find me a source on that one Rampy? It would be appreciated.

 

Greg


 

Don’t have a source, was in the Armory in 84 or 85 and we had a handful of chrome lined BCG & was told by CATM that they no longer were chrome lines and I never saw a chrome one in  M16A2 or M4 

 

Now I could be totally wrong, it’s been known to happen before. 

 

 I’ve never seen what the exact  “mil spec” is and it’s very closely held info last I knew, but I’m sure it’s got to be out there somewhere.

 

Was scheduled to take a class from Will Larson and build one, but his untimely passing.......

 

Now I’m really wondering how far off base I am and where I got my wires crossed...

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I've looked all over the net and everything comes up  as chromed. The last true COLT M16 carrier I had was chromed but who know when it was made. I can't find a US govenment spec sheet but this is an interesting thing. I'll invest some time this afternoon and see if I can run it down. From the FN Military collectors page:

 

The bolt carrier group is, again, Mil-Spec, which means the bolt is properly marked with HPT-MPI indicating it was high-pressure tested and magnetic particle inspected. It and the bolt carrier are phosphate-finished, and the carrier is chrome lined.

 

 

 

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