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Discussion Starter · #1 · (Edited)
I just wanted to post this here as a warning. I don't know what effect bi-metal jackets have in 7.62x39, 5.45, or pistol calibers, but in .223, they eat the barrel up fast. I shot Wolf and Brown Bear at the range and in 3-gun over the past 5 years or so and my SLR-106's barrel shows advanced throat wear, having gone from 2 MOA to 6+ using Prvi Partizan 75gr match. No mag dumps, just plinking and what you'd expect from small-time 3-gun and 2-gun matches.

It may be ok to shoot this stuff in an AR15 since new barrels are relatively easy to obtain and install, but you should think twice before using it in firearms with hard to replace barrels.

I bought one of the old AK-47-pattern Bulgarian 5.56 barrels years ago and am setting money aside while researching who will be willing to turn the barrel down to the proper AK-74/SLR-106 dimensions. It's beginning to look like an expensive pain in the ass.

These barrels are known to get 25,000+ rounds before starting to lose significant accuracy when shooting copper jacketed ammo, and mine is dead at between 6 and 7k.

I hope this warning can save someone else the grief.
 

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Wow, that stinks. I definitely would have expected it to last longer too.
 

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I'll take note and only shoot the copper jacketed ammo in my 5.56x45 AK's.
 

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I'd have to pencil it out, but off the top of the head, I would imagine it's cheaper to buy barrels, than to pay for copper jacketed ammo (vs. CommBloc el cheapo).
 

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Alexei, but the problem with this particular rifle is that you can't get replacement barrels. And, like all AK's, the barrels are a real pain to change compared to an AR15.
 

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Bad news for a lot of us that own these. I don't mind using bi-metal jacketed ammo in my AR because changing the barrel is something I can do myself. I think I'm at roughly 2k though my 106 with all of it being Tulammo and brown bear. :(
 

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Discussion Starter · #13 ·
Yeah, I'm really curious to see if bi-metal wears barrels of other calibers out as fast as it does with .223. .223 is higher pressure and velocity than any other caliber loading bi-metal jackets are used to make, so it might just be the worst of the bunch.

I also wonder if this is just the jacket material or if it's also the powder used. There are surplus powders in the US that burn hotter and will cause faster throat erosion.
 

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Now I'm kinda unsure about the 500 rd of Tula that I bought to test fire my new M-85.
 

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Discussion Starter · #15 · (Edited)
The Tula is absolutely bi-metal. I recommend against shooting a lot of it. Another guy got 40,000 rounds out of his SLR-106 before hitting 5 MOA accuracy shooting copper jacketed ammo. 6,000-7,000 rounds of bi-metal put my SLR-106 at 6 MOA. Something to keep in mind.

Wolf, Brown Bear, Silver Bear, Tula, etc. I don't know of any recently made steel case ammo that doesn't use bi-metal jacketed bullets.

In the early 2000s, Wolf used to use copper jacketed bullets. I think they made the switch around 2007 or so.
 

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I have put probably close to 15-20K through one of my 74 strictly using 7N6. the other beater probably has around 10K. these rifles were both kit guns utilizing original cold hammer forged barrels. My match vepr probably has around 6k maybe little more....I have no effects on accuracy. Again, ammo used was 7N6

it strikes me very odd the fact that you are using hammer forged barrels that were meant to go on a select fire AKs...and after shooting (on your part) semi-fire you barrel is shot? DAIM.
 

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I don't have any belief it is caused by the steel jacketed ammo. 7000 rounds in a 223 barrel is pretty decent. I understand your frustration that its expensive to replace.

FYI a machinist ought to be able to make a barrel from a scratch stainless blank. There's nothing fancy about an AK barrel unless I am missing something. It may cost $500 to rebarrel it though.

You might consider just selling the rifle for half its price and replacing with full disclosure.
 

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Discussion Starter · #18 ·
Voron,

7n6 has a copper jacket (well, "gilding metal" actually, but that's mostly copper and is definitely not a bi-metal jacket).


I don't have any belief it is caused by the steel jacketed ammo. 7000 rounds in a 223 barrel is pretty decent. I understand your frustration that its expensive to replace.

FYI a machinist ought to be able to make a barrel from a scratch stainless blank. There's nothing fancy about an AK barrel unless I am missing something. It may cost $500 to rebarrel it though.

You might consider just selling the rifle for half its price and replacing with full disclosure.
Dude.

7,000 rounds is poor for a chrome-lined 5.56 barrel shot with moderate full auto, much less a cold hammer forged, chrome lined barrel. That such a barrel is shot out with slow and moderate semi-auto fire in only 7,000 rounds is abysmal. It is absolutely the steel jackets or the powder used. Considering .223 Wolf, Brown Bear, and Tula all eat up barrels fast in testing, and Tula uses a different powder, I'd say the bi-metal jacketed bullets are the common factor.

Have you seen this test? http://www.luckygunner.com/labs/brass-vs-steel-cased-ammo/

The biggest issue with rebarreling is drilling the pin holes in the barrel when the trunnion, gas block, etc already have holes. That job requires special equipment and skill to avoid egging out the holes and, like you mentioned, is probably going to cost $500 to have done by the right person. I already have a replacement barrel, as I posted above.
 

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gotcha. good to know the difference. Here is some more info. I just talked to Krebs, he shoots his select-fire 74 using MIXED ammo, meaning both 7N6 and wolf. The round count on that rifle (we shot at least 2 k through it, between 2008-2010 at the big 3) is at least 7K. the rifle is still just as accurate. Keep in mind this is a select-fire 74.

I went back and attempted to remember how many rounds I had through my very first owned AK- RobArm Vepr II in 7,62x39. I understand that AKM round does not have the same pressure and velocity when compared to 5,56....but I estimate I put at least 5-6K shooting EXCLUSEVELY Wolf MC HP 124 grain. This is older stuff that is lacquer coated case and has sealant around both projectile and primer. The rifle never had any problems with accuracy.

I personally don't think its the bullet. One of the things that Marc mentioned was the type of powder that can do such damage. For example- older accurate powder contained silicone, which wore 45s like a rotten whore. 45 ACP is a relatively low pressure round, and the barrels can last a VERY long time with combinations of right powder and projectiles. This Accurate powder was wearing them out extra quick due to its chemical composition.


I would really like to see what is really going. This is interesting indeed.
 
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