case capacity and powder charge
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dryfly
- Posts: 115
- Joined: Mon Jan 13, 2003 10:50 am
- Location: central pa
case capacity and powder charge
Is the relationship between case capacity and powder charge the same with black as it is with smokeless powder? Example: A 7mm Mauser with 50 gr of smokeless gives so much velocity, the same charge in a 7mm mag would give less velocity for the same bullet weight. Would this relationship be maintained say in a 45-70 and a 45-90 with the same weight of bullet, with the same weight of powder change. I am not taking into consideration the compression or the use of fillers in the larger blackpowder case.
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IronSight
- Posts: 226
- Joined: Tue Nov 18, 2003 7:34 pm
- Location: Indiana
dryfly,
I think i understand your question, not quite sure why your asking it though. First of all you have to take fillers or wads into consideration as any airspace between the bullet and powder charge could lead to detonation instead of a more controlled burn rate. Not a good thing. The bullet MUST be seated against the powder charge. In the extreme, this can also be true of smokeless although its more forgiving and harder to detonate.
This is of course, if you want to maintain the same bullet to bore dimension (or overall length dimension) between the two case sizes.
Any given powder charge from the same lott will produce equal amounts of energy under laboratory conditions. The complication is how this energy manifests into muzzle velocity which is determined by numerous variables some of which are compression, primers, neck tension, bullet crimps, bullet seating relative to the bore, bore fouling, etc.
On the other hand, if you don't care about keeping the overall length dimension the same between the two cases and we eliminate all variables for the sake of argument, then the bullet in the 45/90 must be seated much deeper into the case to prevent any airspaces. So we are stuck with an appreciable bullet to bore variance between the two cases. Some of the dynamics which come to mind here that affect velocity are bullet bumping differences during initial ignition and gas leakage can be greater in the 45/90 case especially with loose neck tension.
Dont know if this helps or maybe you knew all this already and i didn't understand the question.
I think i understand your question, not quite sure why your asking it though. First of all you have to take fillers or wads into consideration as any airspace between the bullet and powder charge could lead to detonation instead of a more controlled burn rate. Not a good thing. The bullet MUST be seated against the powder charge. In the extreme, this can also be true of smokeless although its more forgiving and harder to detonate.
This is of course, if you want to maintain the same bullet to bore dimension (or overall length dimension) between the two case sizes.
Any given powder charge from the same lott will produce equal amounts of energy under laboratory conditions. The complication is how this energy manifests into muzzle velocity which is determined by numerous variables some of which are compression, primers, neck tension, bullet crimps, bullet seating relative to the bore, bore fouling, etc.
On the other hand, if you don't care about keeping the overall length dimension the same between the two cases and we eliminate all variables for the sake of argument, then the bullet in the 45/90 must be seated much deeper into the case to prevent any airspaces. So we are stuck with an appreciable bullet to bore variance between the two cases. Some of the dynamics which come to mind here that affect velocity are bullet bumping differences during initial ignition and gas leakage can be greater in the 45/90 case especially with loose neck tension.
Dont know if this helps or maybe you knew all this already and i didn't understand the question.
IF YOU CAN'T MAKE IT WORK..AT LEAST MAKE IT LOOK GOOD!!