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My turn to ask a head space question please.

2K views 7 replies 5 participants last post by  tostado22 
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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