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Barrel Wear and Bimetal Bullets?


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A few of us thought that perhaps what is happening is the powder or primers are slightly abrasive, and a lack of cleaning is what is causing the problem. Or that .223 steel cased ammo has a bad powder primer mix.

 

Interestingly, steel on steel is not that abrasive, especially if the one surface is hardened and the other is softened with aluminum and/or sulfur . However there are a number of elements and compounds in powder and primers that can be extremely abrasive if allowed to build up.. In fact early runs of the new M855A1 (lead free) caused significant barrel wear due to the primer not igniting the powder fully.

 

It is possible that the factory making steel cased .223 does not have an ideal powder and primer for the .223. Which is causing unburned powder to stay in the barrel and subsequent rounds grind that abrasive mix into the barrel.

 

The only way to know for sure would be to pull down about 10,000 rounds of bi-metal projectiles and load them in brass cased ammo of known quality. And then load the steel cased with copper projectiles and fire both types of rounds out of two identical rifles to see what happens.

 

Until then. I'm shooting the steel cased out of my AR-15 since I can replace that barrel easily.

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Csspecs is correct.

 

Barrels are made from steel as we know.  Thing is these barrels under-go two common processes, one or the other.  One is nitro-carberization.  This is the actual name of the process used by Glock and Springfield for their pistols.  It creates a surface layer of steel that is over 80% harder than your average steel that is untreated.  This is very resistant to wear and tear.  A side effect is that rust and corrosion also do not like steel that has undergone this process.

 

But your average AK barrel is hard chrome plated.  This is a plating that is also harder than untreated steel.  It is also resistant to wear and tear as well as rust and corrosion.  While it is not harder than the surface steel that has undergone the carberization process, you will find that your average shooter will still kick the bucket before the barrel needs to be replaced.  That's pretty freakin good.

 

Your bimetal jacketed bullets have a thin layer of untreated steel and an outer layer of copper on top.  This untreated steel is better suited for the jacket because of it's machineability (Ability to be machined or cut/shaped/etc.).  It will expand to fit the lands and grooves as it would be needed.  It's so "soft" that the treated steel or the hard chrome would easily "laugh at it".

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  • 4 weeks later...

It might be that AR rifle barrels are made for copper jacketed bullets typically found in brass-cased ammo and cannot stand up to bimetal bullets typically found in steel-cased ammo.

 

AK rifle barrels are probably made for bimetal bullets and do not get shot out after 5 thousand rounds of steel cased ammo like AR rifle barrels do.

 

There is also the possibility that 5.56 and 5.45 ammo wears out barrels quicker than say 7.62 ammo because the bullets travel at higher velocities.

Edited by tbryanh
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My Saiga does have a somewhat rough throat and what appears to be chrome chips on some of the lands in that area. I may stop shooting bimetal steel-cased .223.

 

I was never planning on shooting steel-cased .223 in my US barrel .223 AK build, so this just solidifies that decision.

 

I may even purchase a spare barrel from AK-builder. They have some of the AK-74 profile 5.56 barrels back in stock.

Edited by mancat
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The LuckyGunner experiment is not necessarily dispositive. A better experiment would be to run 10,000 bi-metal rounds over a year of normal-paced shooting, instead of burning through it so fast that the exceedingly hot barrels become a factor. My guess is that the there will not be a significant loss of accuracy at the end of that. I'd really like to know for sure though.

 

We could crowd-source an experiment on a new 5.45 rifle. 10,000 rounds of bi-metal ammo. It would probably take 30-35 people to chip in $100 each. I should pitch the idea on theakforum.net on the thread in question, but probably not enough people would be interested.

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Upon closer inspection of the barrel, my S223's throat is totally trashed. I haven't looked at it in detail in quite some time, so I didn't notice. The chrome is flaking out and the beginning of the lands in the throat are severely eroded.

 

This rifle has seen very few mag dumps, probably less than two or three thousand rounds in its life, and yes, most of it has been with bi-metal steel-cased .223.

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Looking closely at the throat, I'm wondering if what we've alrways been told about the S223 is wrong. The throat appears to be that of a .223 chamber, rather than 5.56. The lands/leade start immediately after the case neck step-down, rather than after a short gap, as they do in a 5.56 chamber.

 

I'm asking around local gunsmiths to see who has the reamer to re-cut the throat to 5.56 spec, if this is the case. That should restore the throat, as the rest of the barrel is in excellent shape.

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Looking closely at the throat, I'm wondering if what we've alrways been told about the S223 is wrong. The throat appears to be that of a .223 chamber, rather than 5.56. The lands/leade start immediately after the case neck step-down, rather than after a short gap, as they do in a 5.56 chamber.

 

I'm asking around local gunsmiths to see who has the reamer to re-cut the throat to 5.56 spec, if this is the case. That should restore the throat, as the rest of the barrel is in excellent shape.

Hard to say. I wouldnt imagine Russia would go through the trouble to make two separate chambers though, considering they sell the '101/102's as 5.56 NATO rifles. Ya never know though.

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Isn't a Saiga 5.45 supposed to be able to shoot 20k rounds of 7N6 before it's barrel is worn out?

 

If so, is the barrel in the Saiga 5.46 a better quality than the barre in the Saiga 223?

 

Are the bimetal bullets or steel cases in the rounds for .223 different in some destructive way than those for 7N6?l


Looking closely at the throat, I'm wondering if what we've alrways been told about the S223 is wrong. The throat appears to be that of a .223 chamber, rather than 5.56. The lands/leade start immediately after the case neck step-down, rather than after a short gap, as they do in a 5.56 chamber.

 

I'm asking around local gunsmiths to see who has the reamer to re-cut the throat to 5.56 spec, if this is the case. That should restore the throat, as the rest of the barrel is in excellent shape.

Has accuracy diminished?

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Looking closely at the throat, I'm wondering if what we've alrways been told about the S223 is wrong. The throat appears to be that of a .223 chamber, rather than 5.56. The lands/leade start immediately after the case neck step-down, rather than after a short gap, as they do in a 5.56 chamber.

 

I'm asking around local gunsmiths to see who has the reamer to re-cut the throat to 5.56 spec, if this is the case. That should restore the throat, as the rest of the barrel is in excellent shape.

Hard to say. I wouldnt imagine Russia would go through the trouble to make two separate chambers though, considering they sell the '101/102's as 5.56 NATO rifles. Ya never know though.

 

 

That was my original take on the issue, but it just doesn't look that way. Unless the case neck is cut differently than it is on an AR barrel, leaving a gap the full width of the case neck for several additional milimeters, it looks like it's a .223 chamber.

 

The chamber & throat on my Saiga resembles the SAAMI .223 Rem chamber shown here. Notice how the 5.56 NATO chamber has a longer leade before the rifling begins.:

 

uCzYBEb.jpg

 

Isn't a Saiga 5.45 supposed to be able to shoot 20k rounds of 7N6 before it's barrel is worn out?

 

If so, is the barrel in the Saiga 5.46 a better quality than the barre in the Saiga 223?

 

Are the bimetal bullets or steel cases in the rounds for .223 different in some destructive way than those for 7N6?l

Looking closely at the throat, I'm wondering if what we've alrways been told about the S223 is wrong. The throat appears to be that of a .223 chamber, rather than 5.56. The lands/leade start immediately after the case neck step-down, rather than after a short gap, as they do in a 5.56 chamber.

 

I'm asking around local gunsmiths to see who has the reamer to re-cut the throat to 5.56 spec, if this is the case. That should restore the throat, as the rest of the barrel is in excellent shape.

Has accuracy diminished?

 

5.45 has a muzzle velocity several hundred FPS less than 5.56. There is also speculation going around (including on this board) that the Russian .223 loads are using an improper powder for .223/5.56.

 

As far as accuracy goes, I haven't noticed a whole lot of loss of iron-sighted accuracy. It still hits exactly where I aim at 100yd.

 

Scoped, I don't know. I've only shot scoped groups once with the rifle, and I think the group was thrown off by having a handguard-mounted bipod. That was a couple years back.

 

It IS possible that the loss of accuracy from a bit of worn throat leade is less than the total mechanical accuracy potential of an AK rifle chambered in .223/5.56.

 

If I get my additional side-mount in the mail this week, I'll be taking the rifle with me over to my cousins' farm, and I'll boresight my 3-12x .223 scope and see how the rifle shoots.

 

I'm thinking I'll pull the barrel at some point - if the chamber is really cut for .223, I'll have it reamed for 5.56 and reinstall it. Otherwise, I'll part out the rifle or rebarrel it with some other barrel. I doubt I would get much money for a demilled Saiga rifle, so I'd prefer to rebarrel it if necessary.

Edited by mancat
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5.45 has a muzzle velocity several hundred FPS less than 5.56. There is also speculation going around (including on this board) that the Russian .223 loads are using an improper powder for .223/5.56.

 

7N6 has about the same velocity as Russian 223 commercial ammo.

 

Why would the 223 rounds be using a different powder than for 5.45 or 7.62x39?

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Looking closely at the throat, I'm wondering if what we've alrways been told about the S223 is wrong. The throat appears to be that of a .223 chamber, rather than 5.56. The lands/leade start immediately after the case neck step-down, rather than after a short gap, as they do in a 5.56 chamber.

 

I'm asking around local gunsmiths to see who has the reamer to re-cut the throat to 5.56 spec, if this is the case. That should restore the throat, as the rest of the barrel is in excellent shape.

 

Seems that either your barrel is defective or the Russian ammo is defective.

 

Even if your barrel turns out being .223 instead of 5.56, this should not matter as far as the Russian ammo goes.

Edited by tbryanh
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5.45 has a muzzle velocity several hundred FPS less than 5.56. There is also speculation going around (including on this board) that the Russian .223 loads are using an improper powder for .223/5.56.

7N6 has about the same velocity as Russian 223 commercial ammo.

 

Why would the 223 rounds be using a different powder than for 5.45 or 7.62x39?

It's not my theory, you would have to ask those who floated it.. Csspecs makes mention of it aboe.

 

As far as the barrel being defective, maybe. The throat is definitely worn, but the rest of the barrel looks great.

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According to this article http://thefiringline.com/forums/archive/index.php?t-442097.html

 

What appears to be throat/leade errosion could actually be rock-hard carbon build up. If so, Outer's Foul-Out can clean it up.

 

Powderman's post at the end of the article explains this:

 

 

I have a rifle that I bought from my wife's uncle. It is on a Sako action, chambered in .220 Swift, with a 30 inch Hart barrel, Canjar single set trigger, and is in a McMillan stock.

I looked down the bore and saw blackness right in front of the chamber--that all important throat/leade area. The rifle had actually started to keyhole bullets at 50 yards.

Now, my wife got an Outer's Foul-Out for me at Christmastime. I decided to try it out on the Swift. I installed it, following the instructions, plugged it in and let it run for 30 minutes.

I poured the solution out and removed the rod, and decided to run a tight patch through the bore first, intending to follow my normal cleaning routine afterward. I started a patch on a jag down the bore--and the rod stopped dead. Wouldn't move forward at all.

Now, I knew that I had a properly sized patch--I had used them literally hundreds of times before. With that in mind, I decided that it needed a bit of assistance. I broke out the rubber-faced mallet, and started tapping on the end of the handle.

I heard a fairly loud "CRACK!" coming from inside the barrel! The rod moved freely afterward.

What came out of the muzzle was an almost PERFECT sleeve of rock-hard carbon fouling, shot through with yellow copper streaks!!!

I ran another clean patch on the jag--it just flowed down that bore like grease on glass. I then looked into the bore, and it looked like a mirror. Best part is that the throat and leade looked almost brand new.

Try a Foul Out first. You can use it on your other guns, as well, and you might save some money.

 

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According to this article http://bisonballistics.com/articles/an-introduction-to-rifle-chambers

 

Leade is the first thing to erode in a barrel and may not matter that much.

Leade

There is a short section of the chamber in front of the throat where the rifling begins. Rather than have an abrupt step from freebore to fully rifled, there is a conical transition. This is known as the leade. You'll see a few standard angles for this - often it's 1.5 degrees. Honestly, I don't know how much this matters. The way I see it, this is the very first part of the barrel to erode, and the angle will be gone soon enough anyhow, so how much can it matter? I am more than willing to be proven wrong here, but I've never seen any evidence that the leade angle matters much for accuracy, and most shooters I know do not seem all that concerned about it.

All in all, your rifle's chamber is something that is important to understand. Knowledge of your chamber's dimensions and why they matter will help you load ammunition that is more accurate in your rifle, and it will make your brass last longer.

Edited by tbryanh
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Ned Christiansen makes a 223/556 gauge to determine if your rifle is .223 or 5.56.

 

http://www.m-guns.com/tools.php


This thread has alot of info in it: 5.56mm NATO versus 223 Remington Chamber Differences

 

http://www.m4carbine.net/showthread.php?55149-5-56mm-NATO-versus-223-Remington-Chamber-Differences

Edited by tbryanh
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I looked at Ned's reaming tool as well unfortunately it's designed to align in the upper receiver of an AR to keep true, so useless in an AK.

 

I may have overstated how bad the erosion may be, but there is definitely some chrome chipping in the least. The rifling lands in the leade are still deep and well-defined when viewed in the proper light.

 

I will try brushing the shit out of the chamber. I brushed it a little bit before making my first post, which didn't really see a change.

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How to do a chamber casting

 

 

This method uses Cerrosafe Chamber Casting Alloy. The cast can be hard to remove if you wait too long. In that case, you will have to heat the barrel to get the cast out.

Edited by tbryanh
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The Bulgarian, Polish and Russian AKs have life expectancy of 30K+ round before barrel is replaced. After barrel is replaced it has another 30K rounds before receiver is stretched out beyond use.

It seems the me that the problem is NOT in quality of ammo, but in very low quality of US made chrome lining on the barrels.

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I have over 5k through my AR15, 99% was the steel cased - Wolf, Brown Bear, etc. I can hold a 5 shot 2" group at 100yds, 9 of 10 on a 2/3 IPSC at 350yds.

 

Barrel will STILL out shoot MY capabilities .

I don't think the average ak or ar shooter will ever shot our their barrel. If you shoot a hot magnum and shoot scoped you may notice your barrel getting Less accurate over time but I think it still would be acceptableF for all but extremely long range or competition shooting
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The Bulgarian, Polish and Russian AKs have life expectancy of 30K+ round before barrel is replaced. After barrel is replaced it has another 30K rounds before receiver is stretched out beyond use.

It seems the me that the problem is NOT in quality of ammo, but in very low quality of US made chrome lining on the barrels.

I think that is one of the big complaints about Waffen Works' AKs, their low quality US made barrels.

Edited by tbryanh
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