According to MSTN (and others) SPR's are being made with Douglas match grade barrels (chrome moly)

The weapon is selective fire/full auto and they supposedly ran the barrel through some torture tests which it passed.

So this un-lined barrel did pass military torture tests without losing accuracy beyond 1 MOA.

Olyarms now produces a MAXHARD barrel that is like 60 RC and should be far more durable than stock chrome moly



Does anyone have information on full auto tests of Stainless Steel and Chrome moly barrels or why these barrels are not a good idea for full auto guns?


I used to have a 10.5in SS commando upper and I once did 2 thirty round mag dumps on it back to back and found that the barrel was not even warm to the touch (granted it was winter and about 30degrees at the time- but I had allready put about 40rounds of slow semi-auto fire through it and that I considered to be more than enough to warm it up.

I have heard comments of how SS barrels would melt if fired in a sustained full auto format - why?

Not that I know anything specific about the metalurgy involved, but maybe it's a case of the chrome-lined 4150 barrel is good enough?  E.G, a $400 barrel might last 10x, a $100 barrel would last 1x and be completely sufficient for 90% of the use.  So for the tip of the blade that needs the hard-core barrel, they can have stainless, but for units where the weapon is nearly decoration, the stock barrel is fine.

JM$.02

SS barrels don't melt. But when subjected to high heat, they warp much more easily than chrome-moly. So you have to sight SS barrels in again after every firefight -- and soon they just won't hold a sight-in anymore.

It is not a hardness issue. The problem with SS is on a molecular level -- the same properties that allow stainless to be more resistant to corrosion also allow it to warp more easily.

Weapons designers have been trying to find a type of SS that will work with Big Guns for decades, and they still use stellite lining instead.

As far as firing two 30-round mags back-to-back in semi, with all due respect, it's almost impossible to duplicate the heat-generating effects of FA fire in semi. I often fire three 30-round mags back to back in FA -- that's about all I will do for fear of damage -- and that 90 rounds in 15-20 seconds will have the gas tube starting to glow. Touch the barrel area and you'll get a nasty burn -- I still have the scars. And three fast mag dumps are not uncommon in a firefight.

I have also witnessed (not on my gun, thank you!) folks dumping three or four Betamags back-to-back in a '16, and you can actually get the barrel behind the FH glowing (not smoking, I mean glowing red) before the gas tube melts. Now, 300-400 rounds in a minute or two is excessive .... but if my bacon was in the fire, I'd like to know I could do it.

When you are subjecting a barrel to that sort of stress, you want it made out of the metal which has the highest chance of coming out in a still-operable condition.

Beyond the SS-versus-Chrome-moly debate, the milspec for chrome lining is to promote easier extraction under FA fire and heat; to reduce throat erosion under the same conditions; and to increase the bore's resistance to pitting and rust in humid conditions.

With today's technology, though, it's impossible to build a chrome-lined barrel to the same tolerances -- and thus accuracy -- as a match unlined barrel. So the SPR makers are sacrificing some of their margin of durability as a trade for increased accuracy. From the reports I've seen, they are happy with the trade-off.

The 2 mags were auto (I know 2 mags is nothing for most of you but I sure didn't expect the barrel to be cool afterward.) ROF was approx 850RPM  unfortunatly I sold the upper and probably won't buy another SS barrel for it now that I know the info posted above.

Most gov't A2's will be hot after 40rds of semi fire. But for some odd reason it takes about 600-700rds of semiautomatic fire to get the front of the barrel to glow red. I've never seen a tube burst so the rifle gas tube must be pretty strong (I've heard carbine gas tubes blow quicker though).

[b]Thanks for the info now I understand the reason for not using SS.   [/b]

That Oly Maxhard barrel would be a lot more tempting if it was offered in fluted preban variations.