Once a stainless barrel has hit its end of useful life you’ll start seeing accuracy suddenly drop off a cliff. Groups will start growing and shots will be off-call. Commercial chro-moly or chrome-lined GI chro-moly vanadium barrels lose their accuracy edge over a gentler decline slope.
A barrel dies at its throat and muzzle. Your best tool for checking is a borescope, but proof will be on-target performance.
If you’re shooting real M855 or M193 I doubt you’ll notice as that shit will group all over the side of a deuce-and-a-half, relatively speaking. GI MILSPEC acceptance of the gun-rifle combo is within 6 MOA, although real life has it around 1.5 - 2 MOA. If you never shoot past 100 yards you’ll probably never notice.
Military armorers almost all use a throat erosion gage which does nothing except show you how big the throat is and how far your leades may be eroded. These measurements are all relative if you didn’t gage the gun as-new before you started shooting.
A chrome-lined barrel seems to last longer, but borescoping and sectioning still show throats erode and chrome wears and chips on the highest points of rifling leades where bullet ogives initially contact rifling lands.
Wow. This forum is an absolute treasure trove of information. Huge thanks to everyone who replied.
I think, with all of the knowledge I’ve gained here, I’ll be sticking with carbon-steel (nitride or chromed) barrels, as I’m shooting for 3 MOA accuracy; it seems like, by the time a SS barrel reaches this point, it will already be rapidly decreasing in the precision department.
I know; I’m making fun of him with you. That’s why I tried to say I understood you were just relaying and not endorsing it at all. Sorry if that was unclear.
Interesting. Not sure why that was necessary - wish you’d leave GD disagreements there. The technical posts I make that involve quantifiable information should stand on their own and be challenged on their own merits not because of disagreements about religion and politics.
In reading up on high power matches and equipment a few years ago I can across some comments that seemed to indicate that the that the 5000 - 10000 “rule” came from the Military marksmanship units figuring out a “max” number of rounds on average a particular type of barrel could have put through it and not see any loss of accuracy. Then they would just automatically swap barrels and not worry about it. Basically the theory went they have figured they could shoot say 5000 rounds out of X type barrel using Y type ammo and could almost guarantee no lost of accuracy. then rather than get “caught by surprise” at the 5000 round point, automatically change out the barrel.
Assuming that is true, the military has the budget to do this, most of us don’t.
The other source of the 50000 - 10000 round rule seems to be just assuming a 223 would burn out barrels as fast as 308 would. which turned out to not be the case.
I also found credible comments by long time competitors that indicated they could get 15,0000 plus rounds out an AR barrel if they took care of it. basically worked to not over heat it, used the minimum powder charge to achieve their goals etc.
Soooo, what does this mean to the OP. Basically unless you run a max powder load and continually try and fire off a 30 round mag as fast as you can each and every time you shoot your rifle, and unless you get a lemon of a barrel I would think you would get easily 15,000 rounds of life out of it.
At what distance were you wanting to maintain 3moa ?
Imagine what he could do with a proper bench rest gun. I’ll bet he could shoot 0.01 MOA. One hole groups at 1,000. I’d like to take some shootin lessons from this guy.
While you guys are in a BS calling mood, today I shot a five shot, 200 yard, offhand, six inch group, with a 458 Winchester magnum, CZ 550 American Safari Magnum, Leupold M8 4X scope.
My question is at what distance are you needing the sub MOA accuracy? A stainless barrel that is no longer shooting on call at 600 yards can still be hammering at 300 yards. Also, as others have pointed out you need match grade ammo to exploit the match grade barrel. M855 ain’t gonna cut it.
Are you seriously seeing USGI M855 shooting around 1.5-2MOA? The best I’ve seen, spread out over a bunch of different lots, years of manufacture, and Colt barrels has been 2.5-4 MOA. Back when I was shooting commercial M193-type I had several Colt M4s that were legit, repeatable, 5 shots into 1-1.25 MOA (2-2.5") at 200 yards. When I started shooting 855 my standard went from 9 of 10 in the 3" 10-ring to 9 of 10 in the 5.5" 9-ring of a B8 center at 200 yards (for zero confirmation). These days I’m thrilled to do 9 of 10 into the 10-ring with 855— at 100 yards.
262 and 70gr TSX shoot into about 1.5-2MOA consistently out of a variety Colt barrels.
What barrels are you using to get 855 into 1.5-2MOA? That’s about what I can get out of a decent bolt gun with 855.
Also, as to the original question there are some barrels out that that seem to bridge the gap. Barrels like the Centurion/Noveske chrome-lined, hammer forged seem to shoot decent ammo like 262 into about 1MOA with increased durability over a true stainless match barrel. That’s the direction I ended up going on my GP rifle and I’ve been very pleased.
If you don’t mind my two cents, early lots of M855A1 were shooting very well and pretty close to the above accuracy spectrum. Speaking for myself only, I haven’t seen the older M855 green tip do anything close, and even later lots of the A1 settled into mediocrity when I last used it in mid-2011, but was still better than green-tip.
Maybe I can talk Pappabear into running some Real M855 LC through his precision Bolt gun this weekend. And while we’re fouling the barrel with nasty ball powder… we’ll run XM855 to see if it’s any sloppier.
