what happens if you overload ammo?

[Lost Sheep]

I had to laugh

Walkalong, 64 minutes after gofastman thanks me for a clear answer, you come along and blow it apart! I had to laugh.

The point of most of my post is that there is no clear, definitive anwer, which you proved.

(Actually, the "no" is pointed more towards the part of the question that refers to the brass releasing pressure and implicitly protecting the rest of the gun and/or the shooter and bystanders.)

When failure occurs among many components simultaneously, it pretty much doesn't matter which fails first. The steel supports the brass head. If the steel fails, the brass surely will. If the brass fails, the steel might or might not, but even if it does not, the results are almost always unpleasant.

Internal ballistics. A lifetime's worth of study.

Lost Sheep.

 

[Walkalong]

Which came first, the chicken or the egg?

 

[ljnowell]

Which came first, the chicken or the egg

Doesnt matter, the colonel is gonna fry it either way. Same with the chamber and the case.

 

[1SOW]

If you have just enough pressure to blow the brass, then just the brass will blow. If you have enough pressure to rupture the steel, then the brass will blow, but so will the steel.
Somewhere between these two pressures other bad things can happen, like the pics of cracks or large "bulges" in the barrel; but yes, the brass may relieve "some" of the pressure. Some of the pressure will be relieved "bypassing" the bullet.
There are some high-speed pics on the forum of a pistol being fired and showing the gasses exiting the barrel before the bullet. "Some" of the pressure was releved.

 

[Walkalong]

Doesnt matter, the colonel is gonna fry it either way. Same with the chamber and the case.

..

 

[Carl N. Brown]

I have never heard of brass cartridges being designed to vent pressure from the barrel; I have always heard they were designed to expand, seal and contain the pressure. Take the case of a ThompsonCenter singleshot pistol, in which the casehead is completely enclosed by the barrel and breech face: even though brass is softer than steel, there is no way for the brass to give and vent overpressure that would burst the barrel. If overpressure gets vented at all, it is usually where the primer blows out and the excess pressure vents through the firingpin hole in the breech (and the barrel may bulge or burst anyway).

Also, with a lot of smokeless pistol powder that 11.5gr over a 9 gr max is a 28% overcharge by powder weight, but the increase in pressure can be exponentially greater than 28%: the increase in pressure as the charge weight increases is not a straight line, but is an upward curve. Which is why I visually inspect cases for double charges before seating bullets.

 

[evan price]

Consider a cartridge in a firearm that is in battery, breech closed. The brass itself is supported in every dimension externally by steel and has almost nothing except the rim edge exposed. IN order for the brass to fail at all there would have to be some place for the expanding brass to go. Since the brass is surrounded nearly completely by steel, the only way for the brass to expand is either forward towards the barrel (which is restricted by the bullet, even if it is moving) which causes case head separations, or else the steel blows apart. That is why case head separations are so dangerous. They are a tiny bit away from a kaboom.

Think of the brass case as a gasket instead of a mechanical part.

 

[cfullgraf]

Another piece to the issue not often addressed is the rate of rise of the pressure.

An over charge of fast burning powder may reach a lower pressure than one of slower burning but the more rapid rise of the pressure in the fast burning powder may cause more damage/destruction.

Kind of like hitting something with hammer versus pushing on it with a hydraulic press.