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Posted: 10/5/2015 3:12:27 PM EDT
I've done some online searches on this, no dice, thought I'd ask.

I was doing some research on Nitride BCG's. I had originally decided on a Nickel Teflon BCG because of the high lubricity and lubricity after wear. My understanding is that Nickel Boron will start out with a higher lubricity but eventually wear to the point where it is virtually identical to chrome.

I was doing some research on Nitriding (because I wanted to understand it a little better) and I found this link:
http://www.burlingtoneng.com/wear_resistance.html

My question is: I see a lot of companies advertise QPQ Nitriding, why doesn't anyone do a QP BCG? If you scroll in the link and look at the table, you are getting a hard (I want to say 70 rockwell hardness) coating with a coefficient of friction of .12 (ish?), and that lubricity is without lubrication. I have always thought that running AR's "wet" caused just as many problems as it solves because that oil just picks up carbon and turns into sludge. If you could achieve a friction coefficient of .12 dry, why hasn't someone tried that?

I am neither a metallurgist or an engineer, just trying to be as well educated on this as possible. . .
Link Posted: 10/5/2015 3:21:46 PM EDT
[#1]
I believe Adams Arms BCG are a QPQ process BCG, and I coulda swore just yesterday I saw another advertised as such.  Adams Arms/Voodoo Industries calls theirs lifecoat I believe, but it's a QPQ process, or rather another name for Melonite.
Link Posted: 10/5/2015 3:23:57 PM EDT
[#2]
Doesn't AIM Surplus have Nitrided BCGs?
 



Edit: they do.





Doesn't mention the QPQ process though.



Link Posted: 10/5/2015 4:36:10 PM EDT
[#4]
Quoted:
I've done some online searches on this, no dice, thought I'd ask.

I was doing some research on Nitride BCG's. I had originally decided on a Nickel Teflon BCG because of the high lubricity and lubricity after wear. My understanding is that Nickel Boron will start out with a higher lubricity but eventually wear to the point where it is virtually identical to chrome.

I was doing some research on Nitriding (because I wanted to understand it a little better) and I found this link:
http://www.burlingtoneng.com/wear_resistance.html

My question is: I see a lot of companies advertise QPQ Nitriding, why doesn't anyone do a QP BCG? If you scroll in the link and look at the table, you are getting a hard (I want to say 70 rockwell hardness) coating with a coefficient of friction of .12 (ish?), and that lubricity is without lubrication. I have always thought that running AR's "wet" caused just as many problems as it solves because that oil just picks up carbon and turns into sludge. If you could achieve a friction coefficient of .12 dry, why hasn't someone tried that?

I am neither a metallurgist or an engineer, just trying to be as well educated on this as possible. . .
View Quote


Anybody who has experience keeping a large number of AR-15s running will tell you, keep it wet and it will run.
Regardless of how slippery the coating on a BCG is when run dry, the inside of an AR upper needs lube.

In a addition to a bunch of phosphated BCGs, I run one Melonited and several NiB BCGs and they get lubed like my phosphated BCGs. They clean up much more easily, though, and the finishes may keep the rifles running when phosphate BCGs will not... but I still lube 'em.

Joe
Link Posted: 10/5/2015 8:01:21 PM EDT
[#5]
Phosphate absorbs oil and retains it better. Nitride and NiB, not so much (much slicker, nothing for the oil to "grab" onto). I still prefer nitride over any of them (almost as slick as Nib, but without the chance of chipping/flaking off). My trick is to use a VERY light coat of grease on only the critical areas (BCG rails, cam pin, bolt ridge, bolt lugs, and just a tad on the rings). I love this setup as it doesn't run off like oils do, yet remains extremely slick. YMMV.
Link Posted: 10/5/2015 9:04:48 PM EDT
[#6]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Phosphate absorbs oil and retains it better. Nitride and NiB, not so much (much slicker, nothing for the oil to "grab" onto). I still prefer nitride over any of them (almost as slick as Nib, but without the chance of chipping/flaking off). My trick is to use a VERY light coat of grease on only the critical areas (BCG rails, cam pin, bolt ridge, bolt lugs, and just a tad on the rings). I love this setup as it doesn't run off like oils do, yet remains extremely slick. YMMV.
View Quote



That's what I do.  I clean with CLP, wipe it off as much as possible, can't really call it dry with clp.  Use slip 2000 ewg on the contact surfaces of the BCG, bolt and lugs.  Doesn't gunk up with a bunch of blow back crude or dirt/dust.  If you clean a LOT, running wet is fine, but all that wetness attracts dirt
Link Posted: 10/5/2015 11:17:31 PM EDT
[#7]
I fairly sure RCA has Blacknitride.com do their BCG's and they go thru a QPQ process.
http://www.blacknitride.com/whatis.html
Link Posted: 10/5/2015 11:22:55 PM EDT
[#8]
How do you two feel about the bolt being nitrided and not just the carrier? I understand the QPQ heating process can cause problems with the metal conditioning for hardness.
Link Posted: 10/6/2015 10:06:28 AM EDT
[#9]
It doesn't get quite hot enough to damage the heat treatment.

I have a Remmy 700 in .270 WSM that I had almost every part, including the barrel, QPQ'd.  It has had close to 1K rounds through it.  It will shoot clover leaves until you're bored with them.  Cleans up with a few passes of the bore brush as stuff just doesn't stick to it.  Chamber and throat still look almost new.  That WSM round is making some 10000 more psi in pressure than the .223 is rated at.

There really is no downside to it.
Link Posted: 10/6/2015 10:56:31 PM EDT
[#10]
I am not a big fan of salt bath nitriding. Gas nitriding is far more closely controlled. You can polish the part and gas nitride and it will come out hard and  have a polished finish. I prefer a satin finish to hold lube. Maybe not as easy to clean but will last longer. I quit nitriding my carriers. The hardcoat anodized surface in the upper tunnel is in the c scale 65 range. Maybe a little more or a little less. Depends on the type of seal used after color . A standard carrier is in the c scale range of 50-52. I have seen a few at 55. When you nitride them, they are 60 plus. Your carrier is now about as hard as the upper. You may see a slight acceleration in upper wear, I did. In 1993, I bought a 5 gallon bucket of well used 1970's vintage military carriers. No telling how many rounds have been through them. Every one is 100 percent usable with the exception of a few that have some chrome flaking in the bores. Craig
Link Posted: 10/7/2015 8:32:40 AM EDT
[#11]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
I am not a big fan of salt bath nitriding. Gas nitriding is far more closely controlled. You can polish the part and gas nitride and it will come out hard and  have a polished finish. I prefer a satin finish to hold lube. Maybe not as easy to clean but will last longer. I quit nitriding my carriers. The hardcoat anodized surface in the upper tunnel is in the c scale 65 range. Maybe a little more or a little less. Depends on the type of seal used after color . A standard carrier is in the c scale range of 50-52. I have seen a few at 55. When you nitride them, they are 60 plus. Your carrier is now about as hard as the upper. You may see a slight acceleration in upper wear, I did. In 1993, I bought a 5 gallon bucket of well used 1970's vintage military carriers. No telling how many rounds have been through them. Every one is 100 percent usable with the exception of a few that have some chrome flaking in the bores. Craig
View Quote


I have a high round count through a JP QPQ carrier and have run into this situation exactly. The upper has significant wear in it for this reason.
Link Posted: 10/7/2015 10:43:21 PM EDT
[#12]
I suppose chrome and nib will have the same issues? They are both harder than nitride.
Link Posted: 10/7/2015 11:07:10 PM EDT
[#13]
How hard nitride is actually depends on the type of material being nitrided. 4140 will be c scale 60-65. When you test for hardness, how hard the base metal is to begin with will affect the reading. a standard nitride surface is .003-.005 in depth. You can ask for more but it is a waste. Nitride is basically like the crust on a pie. If the underlying surface is soft, it will not support the hard surface well and will have great wear properties but not so good impact qualities. Chrome, NiBor, nitride all have their strong points. I like nitride because it will do everything the others will do and I do not have to make allowances for dimensional changes like with plating. Cosmetically and for clean up, the plating is a little nicer. Craig
Link Posted: 10/7/2015 11:15:21 PM EDT
[#14]
Link Posted: 10/8/2015 12:06:07 PM EDT
[#15]
You guys are all awesome. I've been searching on this topic for weeks and have only found older posts from (2005-2011?) where all the information was pure speculation. Glad you guys with experience are sharing the info. Glad I registered, this thread alone was worth the price of admission. My second question is what about a nitrided Upper? I've been taking a long hard look at the WMD stuff, but the upper is triple what I can get one for at my LGS. Am I wrong in thinking I a 6065 lower will get the job done, but the upper should be 7075? A nitrided or even NiBo upper would let the BCG run smoother with less oil? Also, is there a not $150 option for such a part? Enlighten me, or light me up, I can take it, I'm from the internet.
Link Posted: 10/8/2015 12:52:54 PM EDT
[#16]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
You guys are all awesome. I've been searching on this topic for weeks and have only found older posts from (2005-2011?) where all the information was pure speculation. Glad you guys with experience are sharing the info. Glad I registered, this thread alone was worth the price of admission. My second question is what about a nitrided Upper? I've been taking a long hard look at the WMD stuff, but the upper is triple what I can get one for at my LGS. Am I wrong in thinking I a 6065 lower will get the job done, but the upper should be 7075? A nitrided or even NiBo upper would let the BCG run smoother with less oil? Also, is there a not $150 option for such a part? Enlighten me, or light me up, I can take it, I'm from the internet.
View Quote


You will not be able to nitride the upper as it is aluminum, not steel. WMD makes a NiB upper, but you've already found that.

Personally I would stick to 7075, they don't cost much more than 6061 lowers.
Link Posted: 10/8/2015 1:17:42 PM EDT
[#17]
Question for those who are much more familiar with metallurgy than I am.

Would the increased hardness of the BC compared to the aluminum upper be a consideration for causing excessive wear? Would the aluminum upper then become the sacrificial part? Or would the increased lubricity of the Melonited BC outweigh the difference in hardness?

Or should I just keep the BC as is and properly lubed and not worry about it?
Link Posted: 10/8/2015 8:26:37 PM EDT
[#18]
Over the last 30 years, I have tried about every metal heat treatment, plating and coating there is to the AR. The engine building business has been using nitriding, chrome plating and anti-scuff coatings for ever. I always thought I was way ahead of everyone , being able to see these methods in extremely harsh enviroments and temperatures. Fact is, all I was doing was splitting a gnats ass and making myself feel good. Fact is your basic bolt carrier and upper will go 50,000 rounds if you half way take care of it. I have seen plating fail way to often. Spray on coatings work and will definitely give extra life but  eventually wear off also. I have seen hundreds and hundreds of times ex. valves with nitrided stems, have over 300,000 miles on them and everything in the engines is worn out except the stems on the valves. I know this is not a rifle but that valve runs at 700 degrees plus with very little lube. No bolt carrier even comes close to that abuse. I would take a nitrided barrel over chrome any day. Plenty will not agree and that is fine. If you like bling, plating is the way to go. You can not convince me there is anything better or more durable than a nitrided carrier and it is the shit when it comes to the bolt itself. The bolt is under a high load type friction. If you look at almost every type tool steel there is, once you get over rockwell  C scale  50-55, you start to loose  toughness or impact resistance.With nitriding you can retain a core hardness of 50-55 for toughness and have a surface hardness of 60-65 for wear and abrasion. This is just my opinion based on what I have seen over 36 years. Craig
Link Posted: 10/9/2015 11:30:01 AM EDT
[#19]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Question for those who are much more familiar with metallurgy than I am.

Would the increased hardness of the BC compared to the aluminum upper be a consideration for causing excessive wear? Would the aluminum upper then become the sacrificial part? Or would the increased lubricity of the Melonited BC outweigh the difference in hardness?

Or should I just keep the BC as is and properly lubed and not worry about it?
View Quote


Without lube, you'd probably increase wear on the upper, even with lube it will probably increase wear on the upper.

My situation is slightly different as my upper is Cerakoted. I do understand that the cerakote will eventually wear off (how many rounds, no idea). The cerakote finish itself adds some lubricity to the upper so it is, in effect, 2 surfaces with enhanced lubricity rubbing on each other.

I will probably look into a QPQ nitride BCG and try a light coat of grease. I have plenty left over and I expect the grease will last a lot longer than using motor oil. Maybe I'll try both.
Link Posted: 10/9/2015 11:32:29 AM EDT
[#20]
Discussion ForumsJump to Quoted PostQuote History
Quoted:
Over the last 30 years, I have tried about every metal heat treatment, plating and coating there is to the AR. The engine building business has been using nitriding, chrome plating and anti-scuff coatings for ever. I always thought I was way ahead of everyone , being able to see these methods in extremely harsh enviroments and temperatures. Fact is, all I was doing was splitting a gnats ass and making myself feel good. Fact is your basic bolt carrier and upper will go 50,000 rounds if you half way take care of it. I have seen plating fail way to often. Spray on coatings work and will definitely give extra life but  eventually wear off also. I have seen hundreds and hundreds of times ex. valves with nitrided stems, have over 300,000 miles on them and everything in the engines is worn out except the stems on the valves. I know this is not a rifle but that valve runs at 700 degrees plus with very little lube. No bolt carrier even comes close to that abuse. I would take a nitrided barrel over chrome any day. Plenty will not agree and that is fine. If you like bling, plating is the way to go. You can not convince me there is anything better or more durable than a nitrided carrier and it is the shit when it comes to the bolt itself. The bolt is under a high load type friction. If you look at almost every type tool steel there is, once you get over rockwell  C scale  50-55, you start to loose  toughness or impact resistance.With nitriding you can retain a core hardness of 50-55 for toughness and have a surface hardness of 60-65 for wear and abrasion. This is just my opinion based on what I have seen over 36 years. Craig
View Quote


Thanks. I was really looking for information like this.
Link Posted: 10/10/2015 2:46:22 AM EDT
[#21]
Also how smooth the part is machined will affect how it wears in with other parts. If it is rough and has tool marks then it's going to be rougher on the on the parts that it wears against.
Link Posted: 10/10/2015 12:57:59 PM EDT
[#22]
The ideal surface for a sliding type friction is a plateau finish on one of the parts. Two polished surfaces rubbing together is bad news. First you have a large amount of surface area making contact, and  second ,no way to retain lubrication. I am going to relate to engine building again. Take a flat tappet camshaft. After the lobes are ground precision smooth, the cam goes through a parkerizing process to etch the surface. This allows oil retention between the lobe and the face of the lifter.The same goes for the cylinders and rings in the engine. How many of you have worked on engines with a 100,000 plus miles on them. You take off the heads and still see the cross hatch. What you are really looking at is the deeper valleys created to retain microscopic lubrication so the ring does not prematurely wear out. The peaks of the plateau are very smooth where the part rides. In a properly prepared plateau(or a satin type blasted ) finish, you will only have 30- 50 percent actual contact . Don't mean to rant on, just my college instructor days kicking in. Craig
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