Pressure Changes from Brass Capacity

csteinh

What is the difference in pressure developed by loading the same weight of powder and bullet in a case with significantly different capacity?

As an example, what pressure would you expect from 6.0 grains of unique in a .44 special case with a 240 grain bullet versus 6.0 grains of unique in a .44 magnum case with a 240 grain bullet?

What changes would you expect in the velocity of the two loads?

richbug

The 44 mags will be 10-20% slower assuming that they are both seated with the same amount of bullet inside the case. Pressure will also be lower, and you should expect a less complete burn with more crud and powder residue

B17-P51

The pressure will rise signifigantly in a case of even slightly different capacity. A .223 or .308 load that is completly safe in a commercial case may cause extraction problems or possibly rupture in a military case. The example you cited is an extreme example. So much so that if the cases were reversed, that is. a maxload in a magnum case transferred to the special case, bye bye gun.

csteinh

The issue with commercial 308 and 223 brass versus military brass is what started this thought process. 6 grains of Unique is near max in the .44 special but is below suggested starting weight in the .44 magnum. .44 specials don't generate anywhere near the pressure of the .44 magnum but the effect of excessive case capacity has me very curious.

Highball

The difference between a military 5.56 and a commercial .223 case hase to do with weight/thickness of the brass....typically, the military case is much thicker.
Being thicker walled the outer dimensions still must be about the same as the commercial .223's.
Therefore, the internal capacity must be less.
Lessor case capacity coupled with powder charges meant for commercial cases dramatically increase pressures...more velocity, and rapid pressure spikes..right up to taking the gun apart.

Same basic thing with 44 Mag./44 Special.

csteinh

The answer to part of my question is higher pressure occurs when going from higher volume cases to lower volume cases (commercial case to military case). But what happens when one goes from lower case volume to higher case volume? Initially, it appears to generate lower pressure; but can you go to too little powder in too large a space and have pressure problems?

dcs shooters

There have been rumors of detonation of cases with a low powder charge. Everyone that has tried to duplicate it has not, though.

11b6r

Discussions I have seen on large case/ VERY light charge= detonation- one supposition is that will a really light charge, when placed into a firing position (horizontal) the charge lies only in the bottom portion of the case, and the primer lights the whole charge at once. Resulting in a pressure spike. Don't know, but interesting thought.