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"Death From Above"
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We have pretty much heard from Art, Gus and Ted over the years regarding there perspectives on HS. One question I have that remains unanswered that maybe Gus Art or Ted or anyone for that matter, could please clarify. Understand the concept and the difference between NATO and SAMI go, nogo and field reject. My question still lies with shooting NATO ammo in a SAMI chamber. For my example let's use what I cut my chambers to, 1.631-1.630. My question is simple, if you use NATO ammo in a tight SAMI chamber, do you run the risk of prematurely wearing out the throat of the chamber? I know I read this somewhere during one of my late night surfing session trying to find the holy grail piece of information pertaining to the M14 or on other words my quest for knowledge. Please, anyone respond and set me straight. Thanks in advance.
 

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Gas erosion and the resulting heat are what wear a throat; I guess that would be the short answer, however. Shooting ammo loaded shorter than the maximum allowable length for your chamber/throat configuration would, conceivably, cause said throat to erode more quickly than ammo loaded longer - or at least that's my understanding. It would also likely result in slightly degraded accuracy, since the bullet would have to 'jump' farther to engage the rifling.
 
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The biggest problem with shooting ammunition that is tight in a short chamber is functioning. NATO spec ammo will often not allow the bolt to fully close when the chamber is at 1.630" or even 1.631". This results in higher pressure, possible case failure, extraction issues, and possible damage to the rifle (not to mention the operator). SAAMI spec ammo will reliably function in NATO spec chambers. Other than that the two are interchangable, but it's best to not have a minimum length chamber.
 

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MGySgt USMC (ret)
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The biggest problem with shooting ammunition that is tight in a short chamber is functioning. NATO spec ammo will often not allow the bolt to fully close when the chamber is at 1.630" or even 1.631". This results in higher pressure, possible case failure, extraction issues, and possible damage to the rifle (not to mention the operator). SAAMI spec ammo will reliably function in NATO spec chambers. Other than that the two are interchangable, but it's best to not have a minimum length chamber.
Ted REALLY nailed it here folks, good post!

I am much more concerned about wear and tear on the receiver and especially the heel of the receiver prematurely wearing out and cracking due to firing surplus ammo that is in spec, but on the high side of the spec in chambers that are too tight.

Allow me to give you an example of what was "in effect" the results or more pressure on a Garand Receiver than it was designed for.

When you start shortening barrels from their original length, you are putting MORE pressure on the receiver and parts because when the gas port is closer to the muzzle and the port pressure goes up dramatically. UNLESS you find a way to get a higher tension recoil spring into the rifles or find a hevier or improved design of buffer tube in an AR 15, you are going to wear out op rod or recoil springs faster.

About 10 years ago a customer brought a M1 Garand Tanker to me for inspection. I had to adjust the timing a little, but other than that, all the parts were serviceable. I WARNED him to replace the op rod spring every 500 rounds on that rifle because of the higher port pressure. Well, one year later almost to the day he brought the rifle back to me. The receiver heel was cracked and almost EVERY operating part was worn out (except the bold body) though that showed signs of excessive wear. I could hardly believe it was the same rifle!! He actually had kept a good round count on that rifle and had fired just over 1,500 rounds through it. HOWEVER, he had not changed the op rod spring even a single time rather than the THREE times he should have done it.

If you fire a lot of surplus in a rifle with a minimum chamber for .308, you risk the EXACT same thing happening as happened to that Tanker Garand.

OH, of course an adjustible gas cylinder screw on that Tanker or an adjustable gas plug on a tight chamber semi auto M14 would be WELL ADVISED if you asre going to shoot surplus ammo in a tight chamber AND replace the op rod springs every 1,000 rounds.
 

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"Death From Above"
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Discussion Starter · #7 ·
Thanks very much Gus for your reply. I set up all my chambers at 1.630-1.631 and always shoot the same BH 175gr ammo. I primarily asked this question because of the recent rash of members asking about HS. I read your thread and refer it to others quite often. I am referring to the thread you called, "A little bit of everything to do with headspace". It really explains a lot. I always knew it was bad juju to use Nato surplus in a tight chamber and never did myself. I often see members asking this question and they get the green light without much of an explanation to the op asking.
I was mainly wondering if the throat would prematurely wear out. Or for the re-loaders, if the bullet is set to deep, would that cause premature wear. Also if you use longer throated bullet in a chamber that was cut with a standard reamer rather than one designed with a longer throat. Seems when I ask one question, I always have ten more on deck. LOL I can't think of a bette place to ask or learn.
Again thanks for your replies.
 

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I was glad to see this post today. I just finished a M25 build and had similar questions. 82nd, the post from Gus you referred to was helpful to me as well. This site has been a huge help in teaching me about my rifle.

Thank you Gus, Ted and 82nd for the responses and all the help y'all provide.
 
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