divernhunter said:
I I have some 303brit that is delinked machine gun ammo and it is very hot in my bolt guns. To be honest with you I am not sure about the whys etc.
Well, I have seen specs for some US military ammo, like .30 M2 Ball, or M80 ball, and the specs listed did not mention that the spec was for machine guns only, or bolt action or semi auto rifles only. Neither is there more than one spec (in use at the same time) for ball ammo in each caliber.
30-06 had an M1 spec that was changed to a newer M2 spec between the wars, but they didnt just change the spec for machine gun ammo, the same ammo was linked for MGs and packed in garand clips. In the case of 5.56, the old ball spec was M193, and the newer spec is M855. But the M855, while designed to make the SAW more effective, is also issued for the M16 rifle and M4 carbine. The only M193 still issued is specifically for older M16s remaining in inventory with slower twist barrels that will not stabalize the 62 grain bullets that M855 is loaded with.
Also, my buddy has an AR50. He has never fired anything other than machine gun ammo from it AFAIK. I bought some at the gunshow and had to pull it out of the links before we could shoot it. Never noticed any problems nor any precautionary warnings about MG ammo from Armalite or anyone else.
I do know that full-auto brass is expanded much more toward the base than semi or bolt fired brass. I had 6000+rounds of 5.56 full auto brass and some of it could not be resizeddue to that.The same thing has happened with some 50bmg I have.
Having the brass expand more when fired from a full auto doesnt indicate a higher pressure;
I do know that full-auto brass is expanded much more toward the base than semi or bolt fired brass
The bolt guns confine all the energy(gas expansion) to the chamber and the machinegun does not.
That makes sense; I imagine the expanded cases are due to pressure remaining in the chamber when the cartridge begins to be extracted in the full auto. The logical conclusion to this is that the brass gets less support, and therefore is subject to greater stress in a semi or full auto than in a bolt action. In which case, the bolt action would be able to handle higher pressures than the auto, because after a certain point the cases would fail in the auto due to the lack of support before the end of the pressure cycle. Just like those Glock KB!s that are discussed on The Gun Zone forum all the time. So are you cant be basing your theory that MG ammo is loaded hotter than other ammo on the fact that the cases are stretched more, since you acknowledge that this is due to the way the MG works, not the properties of the ammo.
I have some 303brit that is delinked machine gun ammo and it is very hot in my bolt guns.
Ahh, now that sounds like potential evidence. What other .303 ammo are you comparing the delinked machine gun ammo to? Did you chrono the delinked machine gun ammo and compare it to the other ammo? Of course any military ammo would be different from civilian ammo; I imagine if you are comparing the surplus stuff to new production civilian ammo then the new stuff is loaded real light because the manufacturers dont want to risk blowing up the almost hundred year old guns that it will probably be fired in, whereas the surplus ammo was designed to be full power and be fired from guns that were new, or at least had been inspected periodically by an armorer.
Also, though the US doesnt appear to make machine gun specific ammo, European countries may do so. I have also heard that .308 ammo that was made in countries that used HK type (recoil operated) rifles used different powder, with different recoil characteristics, than the .308 ammo made in countries that used gas guns, like the FAL or M14. That doesnt mean it the ammo was more powerful, higher pressure, or higher velocity neccessarily. Just the potential difference is a sharp kick or a long push. So remember that your shoulder isnt an effective chrono or chamber pressure transducer.
Have you noticed pressure signs when firing MG ammo through your .50 BMG? If so, it may be a problem with your rifle, or a specific lot of ammo that was out of spec due to manufacturer error, or was improperly stored. Do you handload all your .50 BMG ammo? Or do you buy it from some manufacturer/relaoder? If so, they could be selling you short on powder, and claiming that the surplus ammo is too hot for your rifle just to scam you.
All the surplus ammo was designed to be shot in a machine gun, and the army uses the same MG ammo in their barrett semi autos, and most casual shooters use surplus .50 BMG (machine gun ammo) in their bolt actions. Not everyone wants to pay $4 per round for match grade .50 BMG (which, to my knowledge, is not any weaker/slower than the surplus ammo, and might even be hotter in some cases). And getting set up to reload the stuff is a pretty big investment... I would reload if I owned a .50, but since I dont, I just buy linked MG ammo from the gunshow whenever I want to do some big bore plinking with my buddy's AR50.
For more info on the 50 stuff go to the biggerhammer board. They can inform you with the details better than I can.
Did yall discuss this over there? Do you have a link?