Gunsmithing Throat erosion and SS barrels, do they last longer

[bubbapug1]

I own a few AR's. I like one in particular, it has a 24" white Oak match barrel made of SS. I am a bit worried because it gets the bulk of the work in testing loads and for accurate shooting. However, it is Stainless and I know Stainless lasts longer than normal barrels, but HOW much longer?

I shoot TAC through my guns if that makes a difference.

I have a glock with over 10,000 rounds on it and I cannot see a difference in the rifling of the chamber exit as far as throat erosion goes...but rifles are a much hotter round.

 

[aggiesig]

Re: Throat erosion and SS barrels, do they last longer

depends on the loads...

.223 isn't too bad, .22-250 and othe burner rounds you should expect to see accuracy loss after a couple thousand rounds if run hard.

Some of the benchrest hot cartridges will start to deteriorate after 1500 or so.

I'm personally not good enough yet to really notice and I have a few rifles with 2K rounds through them. when My .308 LTR hits 3K I'm going to retire it's barrel not for loss of performance, but because I've always been enamored with the 6.5 variants...


I wouldn't compare a handgun to a rifle, your talking an order of magnitude difference in pressure. I've got a factory Springfield 1911 with close to 20K down it's barrel but it's running at IPSC loads that are probably 8-9,000 PSI (soft shooting cast ammo). A factory .270 pressure curve is getting near 70,000 PSI

pressure=heat=erosion

 

[SDWhirlwind]

Re: Throat erosion and SS barrels, do they last longer

Many will argue the merits of SS over CM for durability with CM usually getting the nod. Alot of variables so don't think there is any good arguement for either that is 100% positive all the time.

 

[Turk]

Re: Throat erosion and SS barrels, do they last longer

http://www.obermeyerbarrels.com/steel.html
Hope it helps.

 

[John L]

Re: Throat erosion and SS barrels, do they last longer

Your barrel should last well over 4000 rounds. If your doing much long range shooting (600yds. +) accuracy will drop off there first. One of my AR service rifle barrels has well over 8000 on it but I only use it for 100&200 yard shooting. Still very accurate up close. It is a Krieger BTW.

 

[Greg Langelius *]

Re: Throat erosion and SS barrels, do they last longer

Learned some interesting things from that link.

Leads me to some wondering about Inconel materials and hammer forged polygonal bores.

Greg

 

[AUJohn]

Re: Throat erosion and SS barrels, do they last longer

Have you worn a .223 barrel out?
I wouldn't worry about it at all.
Shoot, replace if/when with something better.

 

[JJones75]

Re: Throat erosion and SS barrels, do they last longer

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">Learned some interesting things from that link.

Leads me to some wondering about Inconel materials and hammer forged polygonal bores.

Greg </div></div>

A barrel made from 718 Inconel would be awsome and last a lifetime even in a realy hot round , the problem is that it is a major bitch to machine if one were going to broach cut the bore , and it work hardens VERY VERY quick to the point you can't do anything with it if you tried to button rifle or forge the bore. The cost is also about 25x's higher than SS.

Barrels made from 17-4PH stell work very well , the old "black Starr" Accumax II barrels were great and lasted a good bit longer but if you diden't know what you were dealing with you would spend a fortune ruining reamers. I still have a 22-250Ai in one of these barrels thats still pretty accurate (bout 3/4 moa) that started out shooting in the .3's , it has in the neighborhood of 4000 rounds through it with a cfew hard weekends shooting sage rats. Lothar Walther uses a steel thats is very close to the 17-4 (they made the Black Starr blanks) and with a poly bore desgine i think it would last a long time also.

All in all , i think that using good old 416SS and perfecting a surface treatment like melonite would be a much more cost effective answer to longer barrel life

 

[Greg Langelius *]

Re: Throat erosion and SS barrels, do they last longer

My 'serious' barrel is an LW-50.

The Army has done research with bore coatings in cannon tubes. When new propellants began killing barrels after as few as 50rd, they experimented with vacuum deposition, sputtering ionized metals onto the bore surface, choosing tantalum for various reasons. Bore life went up into the thousands.

The problems with process temperatures and environmental offsets was dealt with soundly by the vacuum deposition method, which has nearly no temperature effect on the barrel.

Ceramic liners were also tested. They had issues involving brittleness and hoop stresses. They worked better with prestressing and tube wraps, but are essentially limited to CIWS systems which swap out and discard barrels after each use. Some favorable results were achieved in testing with 5.56 barrels.

Hammer forging would be problematic with Inconel due to the very rapid work hardening you mention. Essentially, you get one whack, and that's about it. I wonder whether roller forging might work. Explosive and/or Hydraulic forming might also be options.

Greg

 

[triaged]

Re: Throat erosion and SS barrels, do they last longer

If you were to try crazy materials I think you would be better off making it a short liner and EDM'ing the rifling in there. There is also the powdered metal option which might make things easier but I would only try that as a liner as well. How do they put the rifling on the Stellite superalloy barrel liners used in some .mil machine guns? How does the junction from liner to barrel affect accuracy?

 

[JJones75]

Re: Throat erosion and SS barrels, do they last longer

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Triaged</div><div class="ubbcode-body">If you were to try crazy materials I think you would be better off making it a short liner and EDM'ing the rifling in there. There is also the powdered metal option which might make things easier but I would only try that as a liner as well. How do they put the rifling on the Stellite superalloy barrel liners used in some .mil machine guns? How does the junction from liner to barrel affect accuracy? </div></div>

I guess EDMing the rifeling is an option , don't know menough about the capibilities.

It depends on what "super alloys" your refering to , some are used for high corosion resistance like 316L , 320 , hastaloy and the like but are to soft for gun barrels and would not stand up to erosion some are used for highstrength and low weight like highend aluminum and titanium , alloys like Inconel were desgines to high strength at high temps like in the construction of rocket exhaust , some turbines and things like that.
Most machinegun barrels i know of are crome lined , thats not the best thing for accuracy but certainly helps.

 

[triaged]

Re: Throat erosion and SS barrels, do they last longer

I was referring to Stellite Cobalt based alloy. I don't know the exact alloy they use in machine guns but I have heard of Stellite being used in some barrels for M60, 1919, and M2 (and I'm sure more).

Here is a paper about Stellite liners in a 5.56 machine gun.
http://www.dtic.mil/srch/doc?collection=t3&id=AD0822736