Questions pertaining to charge:projectile weight ratios

[Naphtali]

I believe the generally accepted "full-power" black powder load for muzzleloading patched round ball is 3/7 (about 43 percent) weight of RB. In The Muzzle-Loading Cap Lock Rifle, Gorning's Formula shows this approximate powder charge:RB weight ratio to yield 1600 fps muzzle velocity, give or take.

In my copy of Muzzleloading with the Champions, published by the NMLRA in the early 1970s Walter Grote, in his slug gun interview, identifies 1:4 charge:slug weight as yielding substantially similar muzzle velocity. Slugs, the subject of the interview, have sectional densities orders of magnitude greater than RBs. Yet lower charge:weight ratio yields comparable muzzle velocities.

What gives?

I know gas blow-by occurs during a patched RB's travel through the barrel. But are other factors contributing to what appears to be a severe combustion inefficiency for RB propulsion compared with propulsion of slugs?

Parenthetically, is the same sort of propulsion advantage occurring with BPCRs - that is, charge:bullet weight is much lower than RB's, yet comparable muzzle velocities are obtained?
***
My questions are specifically not intended to include R.E.A.L. bullets or Minié balls, or non-mallet loaded conicals.

 

[Rifleman1776]

Slugs, the subject of the interview, have sectional densities orders of magnitude greater than RBs. Yet lower charge:weight ratio yields comparable muzzle velocities.

What gives?

I know gas blow-by occurs during a patched RB's travel through the barrel.

Comparing slugs to prb can get confusing.
I'm sure the heavier slug creates a 'hold back' (don't have a technical term handy) effect allowing the powder to burn more effiicently and fully giving the seemingly illogical extra push to the slug.
As far as blow-by with a prb, really I dunno. Probably happens to a very-very minimal extent with a properly patched, lubed and tight fitting ball. And, probably to a greater extent with a loose fitting ball.
I guess I'm just thinking out loud here. What are you looking for with your post?

 

[Dphar]

I believe the generally accepted "full-power" black powder load for muzzleloading patched round ball is 3/7 (about 43 percent) weight of RB. In The Muzzle-Loading Cap Lock Rifle, Gorning's Formula shows this approximate powder charge:RB weight ratio to yield 1600 fps muzzle velocity, give or take.

In my copy of Muzzleloading with the Champions, published by the NMLRA in the early 1970s Walter Grote, in his slug gun interview, identifies 1:4 charge:slug weight as yielding substantially similar muzzle velocity. Slugs, the subject of the interview, have sectional densities orders of magnitude greater than RBs. Yet lower charge:weight ratio yields comparable muzzle velocities.

What gives?

I know gas blow-by occurs during a patched RB's travel through the barrel. But are other factors contributing to what appears to be a severe combustion inefficiency for RB propulsion compared with propulsion of slugs?

Parenthetically, is the same sort of propulsion advantage occurring with BPCRs - that is, charge:bullet weight is much lower than RB's, yet comparable muzzle velocities are obtained?
***
My questions are specifically not intended to include R.E.A.L. bullets or Minié balls, or non-mallet loaded conicals.

The ratio of powder to ball weight changes with the caliber of the RB rifle. 43% of ball weight with a 50 grain ball is 21 grains and is less than many rifle in that ball weight range will shoot well.
43% is fairly close for 50-54 calibers, but its pretty heavy for a rifle shooting a one ounce ball giving 187 gr. I get all the recoil I need and all the power and trajectory at 140.

What gives with slug guns? They are not round ball rifles. Shooting a 550 gr bullet from a 45 caliber slug gun with 1:4 ratio gives 137 gr. Quite a bit for a 45 but if the rifle shoots it well its not a problem in a heavy slug rifle. Though it will make a lot of pressure and erode nipples unless sealed ignition is used.
Round ball rifles vs picket/slug guns are like comparing apples and oranges.
MV are not comparable. I get 1370fps from my 32" barreled 45 2.6" Sharps with 100 gr of 1.5f Swiss and a 530 gr pp bullet. I can get 1900 fps with 90 gr of FFF Swiss from my 54 flintlock with a .535 ball weighing 230 gr. The ball is easier to move and there is a greater area for the pressure to act on. The 45 2.6 likely makes about twice the breech pressure of the flintlock too.
Dan

 

[CoyoteJoe]

Blackpowder is a low velocity propellant and is much more efficient in pushing a heavy slug at low velocity than in driving a light ball very fast. 70 grains of powder is more than 50% of the weight of a .45 caliber ball and will produce maybe 900-1,000 ft.lb. of muzzle energy. Put the same 70 grains behind a .45 caliber 500 grain bullet and you'll get more like 1600 ft.lb. even though that powder charge is only 14% of the bullet weight.
I think we often make a mistake in talking about velocity. Energy is actually a more meaningful measure since energy is what burning powder actually produces, velocity is just one expression of energy. When discussing projectiles of different weight energy is the only common denominator.