Black powder

[Beekeeper]

I know it has been asked before but please forgive an old mans bad memory and lousy search foo.
How much pressure does 70 grains of (say FFG ) powder create?
How much increase do you get by adding an additional 5 grains?

I know you cannot put too much in a case but an old inquireing mind would like to know.
Stems from old age and 50 years of smokeless powder. For some reason smokeless fumes does something to your brain.
Don't know what but maybe if I ponder it long enough it will come to me.

Any way thanks for the info and the aid to an old failing memory.


beekeeper

[John Boy]

How much pressure does 70 grains of (say FFG ) powder create? Depends on the caliber and the weight of the bullet

[Beekeeper]

43 Mauser
>446 boolit
GG to 360 grain
P/P 370 grain

[TXGunNut]

I'd SWAG it @ 14,000 CUP but am pretty sure you already came up with that.

[Chicken Thief]

BP rarely get over 1200bar~17000psi unless you start doing funny things.

The 303 Brit and the Danish 8x58R was both loaded with BP in the upstart of their lives.
A 70 grain solid BP tube would be inserted in the case, and then a full length sizing to form the neck was done.
Both calibers used a (for the caliber) heavy condom boolit. Cant remember the 303 but 225 grains for the 8x58R.
Given this, pressures was/are in a league we can only fear (2000bar~29000psi for the 8x58RD).

I have noticed as pressures goes up the BP will start to burn cleaner and leave less fouling in the barrel. If the weather is right i get a dark "orange" colour almost like new rust, inside the cases. That is called dragons blood, and is a special and rare sulphur bonding due to clean/proper combustion of the BP. It will wanish within minuts!

In general "only" two things affect pressure in a BP shooter.
1) Boolit weight
2) BP granulation

Boolit weight will rise pressure but only to a point as the boolit will accelerate to accomodate the expanding gas. Given the use of corase BP. So adding boolit weight will never get really high pressures (unless it ends as a barrel obstruction!). Likewise will adding more powder only rise pressure to a point where the boolit will exit the barrel followed by unburned BP, resulting in a great big flame.

Fine granulation on the other hand can rise pressures beyond good.
Wery few here are willing to touch of a 45-70 loaded with 80 grains of 4f behind a 535gr boolit, right? I would think that that load is entering smokeless territory.

[Jeff Houck]

Has anyone with a strain gauge set up already conducted some pressure tests using 4F powder, 500gr. bullets in a .45-70? If so, would you be willing to post your results here?

Thanks, Jeff Houck