45 Boolit and Holy Black Velocity Estimate

[TCLouis]

So if one were to dump 60 or 70 grains of FFFG down a 32 inch barrel, shove a 255 grain 45 caliber Pure lead SWC boolit on top of it and then touch the whole thing off with a cap, what would ya think the velocity would be?

[405]

:):):) 232" barrel... that's almost 20 feet! I know that when you touched it off the velocity would be 0. Then I imagine around 20-40 inches down the barrel the bullet would be going about 1400-1500 fps. Some where after the max vel zone it would start slowing down. How fast at the muzzle? Dunno.... but I'd guess quite a bit slower than 1500 fps.

Now, the two things I can think of that may affect all that are: At firing, the column of air in front of the bullet has weight (mass) and could hinder the progress of the bullet so may lessen the max velocity and all velocities during its path thru the bore. And, bullet friction would be variable depending on bullet design, bearing surface, lube, bore twist rate, rifling groove design, etc. so the velocity at any one point would depend on the above bullet/bore variables.

Almost forgot- now my head hurts. Unless that was a typo in the OP then it was interesting thinking about it. If typo then a 23" or 32" ?? barrel would produce about 1400-1500 fps at muzzle with that load I guess.

[rhbrink]

Got my old Lyman Black Powder Handbook out and it says;
230 grain boolit
.45 cal 28" barrel #454616 Diameter .455"
65 grains of FFFG G-O
Vel=1588 FPS
pressure = 15,660CUP

265 grain boolit #454613 Diameter .454'
.45 cal. 28" barrel
65 grains of FFFG C & H
Vel = 1472 FPS
pressure = 14,750 CUP

Now before everybody jumps all over me cause the 265 grain boolit shot with less pressure that the 230 grain boolit it was shot with a different powder Curtis & Harvey versus Gearhart-Owen.

[TCLouis]

405
I have heard that most of a BP charge is expelled and wanted to see if I could get the benefit of that powder if the barrel was long enough. Not good as a brush gun ( the support carriage keeps getting stuck), but I do not have to get so close for the gun to be close.

rhbrink

Thank you so my guestimate was about right.

[cajun shooter]

Half of the charge is not expelled in the sense of going out the barrel. A large amount is left in the barrel as fouling. It may be soft and wet or dry and fluffy. The better powders will only leave a light residue that is taken out of the barrel with the next shot. A powder that is not very good will leave a very hard and crusty residue that has to be scrubbed out or the gun will not chamber another loading.

[405]

405
I have heard that most of a BP charge is expelled and wanted to see if I could get the benefit of that powder if the barrel was long enough. Not good as a brush gun ( the support carriage keeps getting stuck), but I do not have to get so close for the gun to be close.

rhbrink

Thank you so my guestimate was about right.

OK, I see you corrected the typo, so we are talking a normal barrel length like 32 inches :)

If you look closely at published load data for muzzleloaders you can see the "diminishing returns phenomenon" (powder weight vs muzzle velocity curve) develop. It is true even with smokeless powder, just much more so with BP. One of the reasons is, as stated, a large % of BP powder is not converted to gas but remains a solid. IIRC and it's been a while, but barrel length vs muzzle velocity tests have been done with MLs. Not just with regular length barrels from a few inches out to maybe 50 inches but with much longer barrels. It clearly shows, all other things being equal, that barrel lengths longer than something in the 40 inch range will actually show decreased muzzle velocities. Similar tests have been done with the 22 rimfire.