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2 dumb questions

 
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  #15  
Old 02-05-2012, 05:26 PM
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Re: 2 dumb questions

Bart, I agree commercial 308 loads should be safe in gas guns. Handloads are a different
story. Sierra has the best load data for both in their manuals now.
The 223 has always been safe in a 5.56. But in the 70's and 80's there was "the broken
bolt club" for ar's. The higher pressures of the 5.56 rounds appeared to be stretching the
brass into the throat a bit. It was pinching the bullet and driving pressures way up.
Winchester had a decent article on it on their website for years. It's probably still there.
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  #16  
Old 02-05-2012, 07:05 PM
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Re: 2 dumb questions

Quote:
Originally Posted by Loner View Post
Bart, I agree commercial 308 loads should be safe in gas guns. Handloads are a different story.
Why are handloads a different story? Thousands were used by the US service rifle teams.
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  #17  
Old 02-05-2012, 10:24 PM
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Re: 2 dumb questions

Quote:
Originally Posted by Loner View Post
You do not shoot bolt gun .308/7.62 loads in a gas gun.
http://www.saami.org/specifications_...mbinations.pdf

Check the above and nothing's mentioned about shooting 7.62 NATO in a .308 Win. nor the reverse thereof.

It does caution about shooting the 5.56 NATO in .223 Rem. chambers.
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  #18  
Old 02-05-2012, 10:34 PM
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Re: 2 dumb questions

Quote:
Originally Posted by Bart B View Post
Why are handloads a different story? Thousands were used by the US service rifle teams.
It's nothing to do with handloads vs. factory. It's to do with powder burn rates, port
pressures as well as how much powder. Like I said before Sierra has a chapter devoted
to the differences. It's a good read. I believe Speer also has a separate section for gas
guns. This is all pretty old news. And a lot of m1's and m14's have been broken by hot
loads, that is certainly no secret.

exterior ballistics

My last word on it will be this. Few guys struggle to reach 1000 with a bolt 308. It's a stretch for an AR10.
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  #19  
Old 02-05-2012, 10:59 PM
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Re: 2 dumb questions

Quote:
Originally Posted by Bart B View Post
Why are handloads a different story? Thousands were used by the US service rifle teams.
The factory loads are always kept well beneath the pressure limit. Hand loads are ok if the loads are kept mild and not pushed to hard for gas guns. Gas guns cannot run top pressures in their chambers that's why it safe to run factory loads in autos.
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  #20  
Old 02-06-2012, 09:48 AM
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Re: 2 dumb questions

Quote:
Originally Posted by Loner View Post
It's nothing to do with handloads vs. factory. It's to do with powder burn rates, port pressures as well as how much powder.
You're almost right. It wasn't the hot loads (those above SAAMI and MIL SPEC limits) that caused the problems. It was too slow of a powder that made the port pressure too high and bent their op rods.

Both the US Army and USMC rifle teams pulled the 172-gr. bullet from M118 match ammo and replaced it with a Sierra 180 HPMK for use in their M14NM rifles. While that handload put peak pressures up about 10% over normal max, no problems were found.

And the US Air Force and Navy rifle teams removed the bullet and powder from M118 match ammo then put in 44 grains of IMR4320 under a Sierra 190 HPMK for their M1's converted to 7.62 NATO. That load was about 15% over normal max, but none of their Garands suffered in the least.

All the service teams pulled the 147-gr. bullet from certain lots of M80 ball ammo that was loaded by Lake City Army Ammunition Plant with IMR4475 powder then replaced it with either a Sierra 168 or M2 172-gr. match bullet. Both of these handloads had peak pressures about the same as the 7.62 NATO proof load around 66,000 CUP in both M1 and M14NM rifles. Again, no problems were noted.

Quote:
Like I said before Sierra has a chapter devoted to the differences. It's a good read. I believe Speer also has a separate section for gas guns. This is all pretty old news. And a lot of m1's and m14's have been broken by hot loads, that is certainly no secret.

exterior ballistics
That info's well known by lots of folks. Too bad Sierra doesn't mention the thousands of .308 190-gr. HPMK's they sold to the military teams shooting them over IMR4320 in Garands.

Quote:
My last word on it will be this. Few guys struggle to reach 1000 with a bolt 308. It's a stretch for an AR10.
AR-10's shoot bullets just as fast as M14, M1A or M1 rifles chambered for the .308 Win or 7.62 NATO round with the same length barrels. They never had a problem shooting match winning and record setting scores at 1000 yards. That is, as long as they didn't use the M852 match round shooting Sierra 168's in a near worn out or oversize bore...or use a barrel less than 22 inches long.
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  #21  
Old 02-06-2012, 09:57 AM
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Re: 2 dumb questions

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Originally Posted by meatyrem View Post
The factory loads are always kept well beneath the pressure limit. Hand loads are ok if the loads are kept mild and not pushed to hard for gas guns. Gas guns cannot run top pressures in their chambers that's why it safe to run factory loads in autos.
If gas guns can't run top pressures in their chambers, then why is the ammo for both commercial bolt action and semiauto gas versions loaded to the same max average pressure levels according to SAAMI specs? SAAMI doesn't differentiate between bolt or gas gun in their specs for commercial cartridges. Neither does any MIL SPEC for the military versions.

Sounds like you think only "mild" handloads are at SAAMI maximum average pressure specs. Are "normal" ones hotter, say up to high pressure proof load levels?
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