Bimetal jacket

[stubbicatt]

By now I feel comfortable that those who wished to do so have viewed the Lucky Gunner test on 5.56 bimetal jacketed bullet type ammo in AR15's.

In a nutshell the steel jacketed, copper washed, bullets wore down those chrome lined barrels something fierce.

I wonder, do you suppose the same is happening with the 30 bores? Been shooting the cheap steel cased import ammo in my SKS for years now, probably put over two thousand rounds thru the rifle, and I wonder if this choice in ammunition will wear down the bore as rapidly in this rifle as it has done in the Lucky Gunner tests? What of the Mosin Nagant rifles? I reckon it shot a lot of this type of ammo before it was surplused also.

At one time I guess these surplus rifles were throwaway propositions, but I do not fancy the idea of having to rebarrel an SKS, and I certainly do not intend to throw this one away. The M/N I can buy a couple of yet, if that is an issue. I have dies and brass etc for reloading, perhaps I will change over to that at some point in the near future.

Thanks guys for your wisdom on this issue.

 

[shinyroks]

I think the real enemy when it comes to those surplus rifles is the corrosive powder more than the bullets.

Someone correct me if I am wrong, but my understanding is that the surface area vs bullet weight will increase the wear on the barrel more significantly, ie it is going to take more rounds of .30 cal with the exact same ammo/manufacturer than .22 cal to wear the barrel to the same extent.

I personally reload for both of those, it is the best way to pull every ounce of accuracy from the platforms.

 

[briansmithwins]

High velocity and smaller bores shoot out faster. 556 is pretty much the worst commonly used cartridge for burning out the throat.

.30 cal is going to last longer as those bullets aren't usually pushed that fast and because it has a larger bore.

Going to the other extreme than 556: I don't expect to be able to shoot out the barrel in my Uzi in my life.

BSW

 

[stubbicatt]

Hm. That makes sense that a 30 bore would be less susceptible to erosion or wear from the bullet jacket.

Of course I have no way of telling how many rounds were fired through the SKS, but the throat looks good... nice, sharp, rifling as far as I can see with the naked eye.

But this premature wear occasioned by the bullet jackets phenomenon has many implications I think. Many years ago I remember an article in Precision Shooting or something similar where the author compared wear in revolver barrels from jacketed bullets to cast bullets, and the cast bullet barrels evidenced very little wear at all. So, comparatively, steel jackets wear the barrel more than copper or cupro-nickel jackets, which in turn wear the bore more than cast bullets. It all stands to reason, but the magnitude of the difference in wear as detailed in the Lucky Gunner article still surprises me.

 

[briansmithwins]

Any velocity difference between those jacketed and lead slugs?

Powder type enters into bore wear too, as some powders are much more aggressive at attacking the throat than other.

Either way, by the time you wear out a barrel you've spent way more on ammo (or even components) than a barrel is going to cost.

BSW

 

[tahunua001]

those rifles were designed with steel cased ammo in mind. they built their rifles like tanks to compensate. but similarly they reason that those rifles wore down so quickly was because they put those 10,000 rounds downrange over the course of a couple days rather than years, shooting slowly does a lot to preserve barrel life and you could probably get 3 to 4 times more barrel life out of your gun by doing so. your 2,000 rounds of ammo have probably done little, if anything to wear out the barrel. they probably had more wear when you got them than what you have contributed.

 

[ThePenguinKnight]

Don't forget the Lucky Gunner guys were doing constant mag dumps and, in their own words, running it till they were too hot to touch then shooting some more. I believe the continued shooting under excessive heat was the defining factor with the erosion of the bore; bimetal jackets are harder than copper, and will wear a screaming hot barrel much faster than copper will. If you are not getting your gun so hot that rounds are cooking off in the chamber, I would not worry too much about it.

 

[adelbridge]

They burned thru that ammo as fast as they could and I suspect you dont shoot the same pace.

 

[1KPerDay]

1000 rounds back to back? hotttttt

 

[Swampman]

Quite a bit of the US manufactured M-80, 7.62x51 ball ammo has been loaded with copper washed steel jacketed bullets. This includes a lot of the ammo loaded into belts for machine gun use. If the military was worried about increased wear they probably would have specified gilding metal jackets only.
Some people actually prefer the steel jacketed M-80 since, unlike the gilding metal type, it'll actually fragment fairly well at short range.

 

[stubbicatt]

Swampman I thought that MG barrels were to be replaced periodically anyways?

 

[Swampman]

stubbicatt:
True, but then all barrels are consumable items.

The quick change feature on mg barrels is mainly used because the barrels get very hot, most of the time when you change barrels on an mg, you don't throw the old one away. It's merely set aside to cool and then put back in the weapon when the other barrel(s) gets too hot.

My point was that if steel jacketed bullets were actually destroying barrels that much faster than gilding metal bullets, the military wouldn't use them. For most civilians, burning up a barrel is an expensive inconvenience, in a combat situation it can cost not only money, but lives.