BP burn rate and performance

[daschnoz]

Bear with me. There is a question here somewhere.

Think smokeless/cartridge for a second-
We all know that for a given cartridge, as bullet weight goes up, to get optimum performance (muzzle velocity) the burn rate of the "best" powder gets slower . Faster powders may still work, but MV may not be as high as with the slower powder.



Now think black powder-
Does the above hold true for black powder?
I am running 70g of 3F under a 320gr REAL boolit. Would I get better MV if I switched to 2F for this boolit?

[Maven]

You'll get lower pressure, less recoil, possibly more fouling (I'm not convinced of this though.), but less MV than an equivalent FFFg load. You'll probably need to use 80 - 85gr. FFg to get a similar MV in the same bbl.

[Chicken Thief]

Bear with me. There is a question here somewhere.

Think smokeless/cartridge for a second-
We all know that for a given cartridge, as bullet weight goes up, to get optimum performance (muzzle velocity) the burn rate of the "best" powder gets slower . Faster powders may still work, but MV may not be as high as with the slower powder.



Now think black powder-
Does the above hold true for black powder?
I am running 70g of 3F under a 320gr REAL boolit. Would I get better MV if I switched to 2F for this boolit?

Only true in the regards that there is a max pressure not to cross.
1 gram of the fastest smokeless has about the same energy as 1 gram of the slowest. So for smokeless switching to a slower powder will let you burn more before max pressure is reached.

BP will not accelerate burn rate, in the same way as smokeless, as pressure goes up so in essense: If you fill the barrel half way up with powder and then smack down a boolit the unburnt powder will simply be ejected out the muzzle.

For BP: The finer the powder the bigger burning surface and the faster the burn. Pressure will rise slightly (so will MV) but the biggest change is that burning temperature will rise and barrel erosion might kick in.

[John Taylor]

Don't know if this applies. Many years ago while playing around with a mortar I switch from 3F to 2F and the distance doubled with the same volume of powder. There are a lot of "rules" on which powder to use for which gun and I think I broke most of them. 2F works best in my Old Army.

[NickSS]

I use light charges of FFFG in my 50 to 58 cal rifles for two reasons, less fouling and less recoil for a given bullet. This makes sense for target shooting out to 100 yards or so as velocity means next to nothing if the load is accurate and the sights set for the load. When using the same guns for hunting I mostly use FFG and heavier charges to get velocity up for more power and flatter trajectory. Of course I need to set the sights for the load.

[Alan]

Generally, 2F will take more powder to give you the same velocity as a 3F charge, but will do it at lower pressure. This generally translates to higher attainable velocities for a given pressure before you begin to have patch or leading issues.

It can also mean "softer" recoil. One of the things that has got me to switch to muzzle-loaders for all my heavy rifles is that I just can't take the recoil from a .375 or larger gun any more due to shoulder problems. I can shoot my .72 with 120-140gr of 2f or 1f all day with no discomfort. On paper, it should be recoiling as much as a .458, but it's more of a hard push than a whack.

Stock design is critical though - 120gr of FFg is all I want to shoot in a .54 T/C Hawken with a PRB. Most of my T/C's are Renegades for that reason. My .72 is a Pedersoli Gibbs, the .62 I'm having built is a Rigby, and my .66 is a Christian Springs.