2 dumb questions

[Loner]

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.

 

[Bart B]

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.

 

[Bart B]

You do not shoot bolt gun .308/7.62 loads in a gas gun.

http://www.saami.org/specifications...1-Unsafe_Arms_and_Ammunition_Combinations.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.

 

[Loner]

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.

 

[meatyrem]

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.

 

[Bart B]

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.

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.

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.

 

[Bart B]

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?

 

[meatyrem]

Well I know its true with the auto and pump rifles chambered for the 280 rem, for example, which is why they down loaded the factory rounds, or the saami limit is kept low for the autos and pumps because the autos I know it can't handle the the full capabilities of a full house 280 rem. And with the varying differences in the burn rates yes I'll agree on that

 

[Bart B]

Well I know its true with the auto and pump rifles chambered for the 280 rem, for example, which is why they down loaded the factory rounds, or the saami limit is kept low for the autos and pumps because the autos I know it can't handle the the full capabilities of a full house 280 rem. And with the varying differences in the burn rates yes I'll agree on that

SAAMI specs for both the .280 Rem. and .30-06 are the same; check out:

http://www.saami.org/specifications_and_information/publications/download/206.pdf

What commercial ammo company provides those reduced loads for use in auto and pump rifles? Never heard of such a thing. And SAAMI doesn't mention this in their unsafe ammo vs. rifles info available on their web site. Remington's web site for ammunition has nothing about this issue. I think someone's been pulling your leg....or other body part.....too much.

 

[backwoods83]

Bart I agree completely, but some people still think the spring system/buffer in an M1 or the like that is older can't take the abuse, my theory, and plain fact is pressure is pressure if it rated to 61k psi or 52k cup then for liability reasons it must be able to handle atleast 125% of that or it should have been tossed from the get go.

 

[meatyrem]

Hahaha. That is funny Bart. But the Pressure ceiling for the 280 rem ( from saami ) is kept at 60,000psi when other like cartridges such as the 270 has a higher ceiling

 

[backwoods83]

Meatyrem I don't think your seeing the point, yes the 25-06 and 270 are 2k psi higher than 280 and 30-06, doesn't mean it won't handle it, for instance 264wm, 7mm rem mag, 338wm, and 458wm all use the same case dimensions other than neck size but all have different saami spec ratings actually leaving the most popular of those on the bottom, so just what is it you are trying to prove. As I mentioned earlier you can take a load that runs really hot in one of your rifles and in under an hour the throat can be modified to where that load is normal, the original poster asked a simple question, it has been answered, no need for a ****ing contest.

 

[meatyrem]

Not trying to prove anything just discussing. I don't really think anyone is wanting a ****ing match, not even me. But this is a discussion site too and all I am doing is trying to discuss something and learn too. That is the real reason I'm here is to learn and don't get me wrong I'm not saying I know it all just going on past reference

 

[backwoods83]

Yeah, I wasn't trying to be an ***, just a lot of people are under the assumption that semi's and pumps won't take the pressure, they were told back in the day that the springs in the M1s and the like weren't strong enough, not the case, they were, just when most people picked. them up they were wore out. The rem 7600 is a good example as well, they were often chambered in 280 and 30-06 but they will handle hot loaded 06 rounds, primers completely flat, its like setting up a glock or sig to constantly run +p loads, its a simple matter of using a higher tension spring.