Polish new nitrided barrel's chamber?

[ABNAK]

Got two of the righttobeararms 16" Bushmaster (BFI now) barrels, one for my pile-o-parts and one for my buddy. Ostensibly nitrided. Now I am NOT a fan of nitriding (I prefer chrome lined > nitrided > untreated), but for $79 I couldn't pass up on it.

I have read where due to the nitriding process the chamber (and even the bore) can be a little rough unless having been "finished" afterwards. Can this be accomplished via a little steel wool applied appropriately?

I've only had one nitrided AR barrel and at a carbine class where I was firing 5.45 Wolf I had several failures to extract, and had to be beat the case out with a cleaning rod. I haven't had a nitritided barrel since then.

I won't be shooting steel case as this will be 5.56 as opposed to 5.45. I would still expect it to properly function and be able to leave a round in the chamber between strings and not have it stick.

A little "elbow grease" and polish the chamber? The surface hardness of nitriding is up there so I doubt it would hurt it (?).

[kirkland]

As far as I know the nitride process does not change the dimensions of the steel. The barrel you mentioned that you had before probably would have been a piece of junk whether or not it was nitrided.

[1168]

Sarn’t, those dimensions are mostly locked in, for better or for worse.

[constructor]

Got two of the righttobeararms 16" Bushmaster (BFI now) barrels, one for my pile-o-parts and one for my buddy. Ostensibly nitrided. Now I am NOT a fan of nitriding (I prefer chrome lined > nitrided > untreated), but for $79 I couldn't pass up on it.

I have read where due to the nitriding process the chamber (and even the bore) can be a little rough unless having been "finished" afterwards. Can this be accomplished via a little steel wool applied appropriately?

I've only had one nitrided AR barrel and at a carbine class where I was firing 5.45 Wolf I had several failures to extract, and had to be beat the case out with a cleaning rod. I haven't had a nitritided barrel since then.

I won't be shooting steel case as this will be 5.56 as opposed to 5.45. I would still expect it to properly function and be able to leave a round in the chamber between strings and not have it stick.

A little "elbow grease" and polish the chamber? The surface hardness of nitriding is up there so I doubt it would hurt it (?).

Yes, for whatever reason the chambers get sticky after the first warm up, like the stuff comes out of the pores or something. Most of the time it may cause short stroking for 5 shots then it will be fine, only once in a while when someone shoots hot reloads combined with a new chamber will they stick. We have produced around 70000 barrels since 2012, I've tried polishing before fired but it does not stop the chambers from getting sticky It must be done after you fire the first 10 shots or so. Pick a bore brush apx chamber size then wrap a few patches round it. Iosso bore paste is more abrasive than Jb or Flitz. use a short piece of cleaning rod and a hand held drill to spin it for maybe 30 seconds.
I know everyone here loves chrome lined barrels, I don't and haven't used one in 15years. I don't shoot full auto and I've found nitride barrels to be much more accurate than chrome lined. I've never worn out a nitride treated barrel, the surface is twice as hard as stainless and someone ran a test with a stainless barrel and fired 40,000 rounds before the bullets started to tumble. When he removed the muzzle device he found carbon had built up on the muzzle to the point the bullets were hitting it on the way out. If a stainless will last 40k and Nitride is twice as hard I'm okay with spending $200 on a barrel after shooting $10000 worth of ammo through it.

[26 Inf]

Consider one of these?

http://www.brushresearch.com/brushes.php?c2=183

Available in 400 and 800 grit.

[mpom]

NO
Way too abrasive!

[bamashooter]

On a 5.56 and .300, I've used a .38 mop with Flitz. Mop is on end of length of cleaning rod which is chucked into drill. Approx 60-second sessions 6, 7, 8, 9, 10 times. Preceded by chamber brush cleaning. Just depends on degree of roughness. To/fro the length of the chamber. Vary speed if you want. Worked great. Automotive wheel polish would probably do same as would an abrasive toothpaste. Clean well afterward. I spray thoroughly with brake cleaner to get any residue out of nooks and crannies. Lightly lube afterward. Don't activate drill when mop is outside of chamber. You'll sling stuff everywhere. You're just looking to smooth the chamber surface.

[mpom]

No need to go crazy on polishing. Am not a barrel maker, so would like to hear if the idea that too polished a chamber can lead to excessive bolt thrust, since the case wall is not adhering very well to the chamber wall.

[Disciple]

No need to go crazy on polishing. Am not a barrel maker, so would like to hear if the idea that too polished a chamber can lead to excessive bolt thrust, since the case wall is not adhering very well to the chamber wall.

I don't know about polishing but lubrication dramatically increases bolt thrust.

"Effects of Lubrication and Pressure on Bolt Face Forces", by Michlin, South and Brosseau, Weapons and Materials Research Directorate, Army Research Laboratory, October 2010:

Abstract:
"In this research, the effects that the level of lubrication has on the case mouth pressure and bolt force of a M16 are quantified. The case mouth pressure and resulting bolt force were measured for M855 and M855A1 cartridges as a function of the level of lubrication in a modified M16. The research found that the level of lubrication on the ammunition, and specifically the lubrication between the cartridge and the chamber of the weapon, greatly changes the level of force on the bolt face. The average difference between the conditions of heavy and normal lubrication was found to be 3000 lb. This force is a linear function with the peak pressure of the cartridge case and the peak forces on the bolt occur prior to the unlocking of the bolt and projectile exit. The results of the experiments are presented and the ramifications of the force on the M855 cartridge case are discussed."

For reference, the average normal (measured) force on the bolt at 70 degrees F, with M855 ammunition 2073 pounds, with M855A1, 2560 lbs. At the same temperature, but with a heavily oiled cartridge case, the measured force on the bolt face was 5230 lbs for M855 and 5796 lbs for M855A1

If the ammunition temperature gets to 125 degrees F (which is easy to do if left in direct sunlight for some time) the numbers are:

M855
normal - 2526 lbs
oiled - 5553 lbs

M855A1
normal - 2721 lbs
oiled - 5875 lbs





Outside of the chamber, I will agree that there is no such thing as "too much oil", inside the chamber, things are different.

[ABNAK]

Consider one of these?

http://www.brushresearch.com/brushes.php?c2=183

Available in 400 and 800 grit.

Thanks old-timer! Good to hear from you. I ordered one with the 800 grit.

I would assume with the bore itself that shooting will "polish" it?