Okay I know this has been brought up before but I never really got a clear answer that satisfied my curiosity.  I have been building a DPMS style .308 for some time now and my want for a Melonite treated barrel is holding up the show  The specs on the Rainier Arms Select 16" SS .308 Barrel are what I'm looking for minus the Melonite of course  I have looked into WMD Guns and they offer treatments for Melonite and their reputation seems good but I have heard that you never want to Melonite an AR style barrel after assembly because the heat involved in the process will cause the barrel and the extension to expand and contract at a different rate and will effect the torque of the extension causing it to loosen.  Can the extension be removed allowing it and the barrel to be treated separately and then retorque the extension to the barrel?  Should I forget about the Melonite and move on or is this treatment possible on an assembled barrel?  I appreciate any insight you can offer

AR Performance.com

I have had three AR barrels done by WMD with no issues so far.  I have seen increased velocity in my 18" BHW barrel - the only one I could compare against an untreated barrel.

There is always the chance that something could go wrong, and I did ask them about it.  They repsonded that they haven't had any issues with customers' barrels.  I was willing to take the chance.

I don't see that being a problem.  The barrel is threaded into the extension and pinned in place. Warping from nitriding is minimal to non exsistant.

Lots of nice choices here!!

http://ar15performance.com/barrels?cmx=11562&start=15

Thanks, this makes me feel a little better.  I am curious how many rounds have you sent down range since treatment?

Thanks, I apprreciate the link but I am looking for SS sub moa and I'm not wild about their barrel contours

Just because a barrel is SS doesn't make it more accurate, infact SS can be MORE DIFFICULT to properly machine to spec (which is why ARP doesn't use SS).  I guarantee you that you will be hard pressed to beat the accuracy possible out of a ARP barrel.  Their 5R poly rifling is VERY accurate, and most users can't even shoot as well as the barrel.

I can appreciate that but I am a very particular person is all, I know what I want.  Plus they are out of stock

SS doesn't magically make a barrel more accurate.

CM/CMV steels are a better choice for nitride than stainless.

If you're looking for high end performance might take a look here:
http://riflebarrels.com/products/ar_10.htm
Looks like he might have some 18" CM barrels in stock.  16" for a 308 would apparently be a custom order.

This.  In fact there are some cases where salt bath nitriding a stainless barrel will make it LESS corrosion resistant!

Best answer is to either find one already done or see if you can buy the barrel and extension before assembly.

As for the AR 15 Performance barrels the 5R rifling was used in the M-24 Sniper rifle forever.  It will outshoot you and their prices are hard to beat.  I have a Ranier select though and I am truly happy with it, as it will outshoot me as well.  It is stainless but satin finished in the white because that was the color metal I wanted (to match my NiB trigger group).

If you are wanting Melonite though the stainless is moot.  One of the properties of carbon nitriding is the extreme resistence to rusting.  I had a Remington 700 barrel nitrided and it started life as a Boone and Crockett model in .270 WSM with factory fluting.  That thing is scary accurate, and a breeze to clean.  I'm approaching 1000 rounds in it and you can't even see anything that would be called "wear."  From the factory it was button-rifled carbon steel and it will outshoot things that cost multiple times what I have in it.  Believe the folks here that you would not be disappointed if you went that way.

Other than for corrosion resistance (obviously unnecessary for stainless barrels) Melonite offers no real benefit to barrels in AR pattern rifles.
There is no performance or accuracy benefit.
Most AR owners will not wear out a barrel, even in 7.62 NATO/.308, but if they do, the money saved skipping the nitride bath treatment could easily be put towards another barrel, a much better investment IMHO.

Joe

One of the reasons that I wanted SS was for it's already corrosion resistant properties and the Nitriding was to add hardness beyond that of chrome lining.  The idea of it making the SS less corrosion resistant is something that I was not aware of assuming this is fact  I've read quite a few forums on the debate between SS barrels and CM/CMV barrels as far as accuracy and SS seems to have an edge, a very very small edge but still an edge.  I'm no expert marksman, I just want the best results (for a reasonable price) to help calm my OCD tendencies.  I love picking your brains and I appreciate everyones help and advise  So if Nitriding is best on a CMV barrel and SS is better off without it then what do you think would be better for my little .308, a SS barrel or a Nitride CMV?

As has been said, it is hard to beat the performance to price ration that AR Performance offers.  They also already come salt bath nitrided, so you don't have to worry about it.  Not many match barrels come salt bath nitrided, esp in .308!  I would call up ARP, see when they are expecting more of the barrel you want, and wait.  It'll be worth it, esp if you want "the best".  

BTW, light weight handy profile beats by far a heavy boat anchor profile any day of the week, esp if you ever have a desire to take it to the field (hunting, self defense, SHTF, etc).

Just out of curiosity I checked out AR Performance.
Result: SOCOM 5.56 barrel ordered.
I have all the other parts to complete an upper already.

Thanks to this site, any plans I had of early retirement are fading away.

Joe

Nitrided CMV is much more corrosion resistant than stainless, salt-bath nitrided stainless loses corrosion resistance.

It all depends on what qualities you are looking for.

If you're a benchrest competition shooter, you probably wouldn't be here first off, but you'd probably just stick with the tried and true stainless.

If you're not, I would probably get nitrided CM/CMV for the corrosion resistance as well as heat/erosion resistance and longer barrel life.  Then again you wouldn't be building a 308 AR if you were a benchrest competitor, so I'd suggest this route.

About 3-500 each...

Thanks Blain and Gamma762!  You've brought some things to my attention that I never knew.  Now that I've had a little more light shed on this subject I'm thinking a Nitride CMV barrel will be more to my liking

I have nitrided over 80 barrels with extension installed. Zero problems. You will have a hardness of around c scale 60-70. Chrome is similar. Non treated is in the range of 28-32. Life should increase dramatically, accuracy I have not noticed. If extension is torqued properly, and temp is not excessive, you should be fine. You need to know what temp the barrel is stress relieved at, getting to close or going over that could cause problems, according to barrel manufacturer. my barrels were 4140. Stainless nitrides at different temp. I do not no what that is. It also helps with gas port erosion. Make sure chamber is right first, you will waste a reamer, even carbide, trying to resize. It will also decrease bore and chamber I.D. by .0001-.0002.    Craig