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Discussion Starter #1
Hey guys, does anybody knows, is it 5000, 10000 or 20000 or more before replacing? Thnx
 

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Definitely not 5000. I had one with over 6000 and when I finally cleaned it, then I got same accuracy when it was new. Expect easily over 20000 with non degraded accuracy. Replacement? 100,000...?

BTW Did you ask same question on my blog?
 

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So you have your answer in both places then :)
 

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since there is no chrome you must replace the barrel every 500 round

I know this to be true because I read it on a AR forum

lol
 

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Non-chrome/non-treated but appropriate alloy steel I'd say will last *probably* upward of 20,000 rounds before severe accuracy degredation is apparent. Chrome same said steel and add another 15,000 rounds to the life, QPQ nitride and add probably double that.

I say *probably* above because I don't know for sure as I havn't put 20k rounds through my MR556 yet nor do I know anybody who has.
 

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I can tell you for a fact that the MR556 barrel is not nitrided.

If it had been, my adventures in barrel profiling and cutting it back to 14.5 to pin and weld the flash hider on would have been far, far different. I would have had a post in here about having to buy new bits for the lathe.

Nitriding is a fantastic process and I am very much looking forward to having my barrel QPQ nitrided this month. Insofar as i'm concerned, nitriding will make my barrel superior to a 416 barrel in all aspects once it has been nitrided.

I, for one, am very glad HK did not nitride the MR556 barrels. By not doing so, they made it so that we (people who like to Mod HK import guns) can have the exact barrel profile we want, length we want (16.5 inches and less), and add then nitride.

As far as i'm concerned, this is proof to me that HK actually is paying attention to the US civilian market and while they know that they are hobbled by US import restrictions to release neutered, crappy versions of their good guns, they at least give us the raw materials to make versions that are closer to what we want, whatever that want may be.

To be honest, if HK had factory nitrided the barrels, I wouldn't have bought an MR556 to begin with. I'd have a scar or something else in my stable instead.

For what it's worth, thank you HK for shipping these things to us in the raw like you did. Makes project gunning much, much easier.
 

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Discussion Starter #9
Thnx for the informative reply, I guess I might confused with another AR that I have. If I have mr223, by cghanging barrel to 5.56 will give me ability to use 5.56 and .223 or anything else required. I am in Canada and did not see 5.56 model here.
 

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Thnx for the informative reply, I guess I might confused with another AR that I have. If I have mr223, by cghanging barrel to 5.56 will give me ability to use 5.56 and .223 or anything else required. I am in Canada and did not see 5.56 model here.
You can use 5.56 in MR223. Chamber in those are ".223" per CIP specification, not per SAAMI*. Difference is that CIP specification is same for .223rem and 5.56 NATO. My old MR223 had over 5000 rounds of 5.56 NATO ammo on it and probably have at least 2000-3000 more since I sold it.

* - it is UNSAFE to shoot 5.56 ammo in SAAMI spec .223 chamber/barrel.
 

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If the nitrined barrel would last for ever, how come the sig barrels are very often replaced after 10000 rounds?, mine 551 did and so did my shooting buddys 550, both barrels was keyholing after that magig 10000 line.
And both was 1/7 twist.
 

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The barrel life estimates are more than likely estimates based upon using the barrel as a bench rest rifle. You can destroy a barrel if you really tried in 5k rounds.

If you take the rifle to some of the higher rate o fire classes often then life will be shorter.

Doing repeated magazine dumps make little sense to me; that isn't the role of a carbine. Doesn't mean you may not have to do this in the near future (not hardly) but it's a waste of ammo to repeatedly do this.

If you USE the carbine in hard use classes expect to start to lose accuracy around 10,000 rounds.

No barrel will last forever - not even cold hammer forged, polished, cryogenically treated, nitrocarburized barrels. The throats will be eaten away over time.
 

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yes i know that every machine will wear out evetually if u use them, thats why its so funny that some people think that there are some macigal
barrel somewhere that will last forever, no matter how much you shoot through it... it wont happen..
 

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If the nitrined barrel would last for ever, how come the sig barrels are very often replaced after 10000 rounds?, mine 551 did and so did my shooting buddys 550, both barrels was keyholing after that magig 10000 line.
And both was 1/7 twist.
Something tells me your barrels weren't nitrided.

Civ models or mil models?

I"m guessing Civ (SP) models.

Military Sigs are required to be able to perform much better then you describe.

See: http://www.biggerhammer.net/sigamt/550/550techinspection/

And nobody said nitrided barrels will last forever, just significantly longer then untreated barrels and to an extent, longer then even chrome lined barrels and will also have the added benifit of better corrosion resistance then chrome as well.

Having processes such as nitriding is not some magical, unicorn tears treatment, it's simply an investment into the weapon to ensure that it performs to the best of its capabilities for as long as possible.

Fact of the matter is that even at the height of the unpleasantness in the middle east, when our (the US) operational tempo was at its height and our military was literally burning through hundreds of thousands of rounds per training or range session, they still didn't burn up barrels in 10K rounds like you describe.

That being said, if your sig barrels were nitrided and you and your buddy burned them out in 10k rounds, the problem isn't the gun, it's you.
 

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It was 551-2 swat model and it had a nitridet barrel, and ammo was south african surplus.
The sig is making new spare barrels for 550 line rifles so there must be someone else too who need a new one like i did.
 

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Running any barrel full auto will kill it quickly.

How were the guns actually used?
 
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