45/70 Power from my .45?

[Mavrickbobsr]

If i had a .45cal muzzleloader and i put 70 grains of powder under a flat nose or ball bullet would it be the same as shooting a 45-70 cartridge round? Would the speed and energy be about the same?

 

[bubba.50]

Due to the confinement of the case, the primer bein’ right on top of the powder, and the bullet bein’ crimped to keep it in the case it will build more pressure quicker and be a bit faster & more powerful than the same weight conical over the same weight powder charge.


Now get ready to hear about how we don’t discuss catridges or cartridge arms here.

 

[Tom A Hawk]

Not RB but if you had a 405 grain conical, it might be rather close. In my ( unmentionable by 9 years ) Sharps, I shoot 68 grains Swiss 1 1/2F under a 515 grain bullet.

 

[fleener]

In essence, yes. You will lose a little from the nipple. Very little I think. My platinum lined nipples have a very small flash hole. Also depends on size of the bullet. A ML the bullet has to bump up to the rifling since you load from the muzzle. Quite a few BPCR shooter will shoot a bullet that groove dia. not land dia., so that will make some difference as well.

Fleener

 

[bubba.50]

May not be super drastic but, run them over a chrono and I believe you’ll see a pretty significant difference.

 

[Col. Batguano]

Barrel length will be a significant factor. Trapdoor Springfields have 32" barrels (infantry version). Also, the bullet fit in a cartridge gun will be tighter, so there won't be the blow-by you get with a muzzle loader. The 45-70 shoots a .458 bullet, and you's be hard pressed to get that size bullet down a ML'er bore.

 

[Zonie]

Because the question is not about shooting a cartridge gun, it is acceptable on the forum.

As for my answer, the muzzleloader shooting the equivalent of a .45-70 cartridge will not have as much velocity or power.

A significant amount of gas does leak out thru the nipple and even more of the gas pressure will blow past the bullet thru the rifling grooves as it travels down the bore.
Because the slug needs to be smaller than the bore in order to load it, even if it is pure soft lead it isn't likely that the rifling grooves will be totally blocked off by the slug when the gun fires. This is especially true if the barrel has deep rifling grooves.

I have a barrel that is made for shooting lead slugs and the rifling grooves are only a couple thousandths deep.

 

[yonderin]

Round ball won't perform the same due to lesser ballistic ability. A boolit could conceivably come close.

This only possible if you can get the same degree of obturation as the cartridge round. Which isn't likely.

 

[SDSmlf]

Believe the old Trapdoor load pushed its 405 grain bullet about 1400 FPS. Easy velocity to do out of 45 caliber muzzleloader, but if not done right you may have accuracy problems. As others have suggested, shoot over a chronograph if you want to understand velocity. I use a RCBS 11mm rifle bullet that IdahoRon originally suggested in a setup very similar to what he uses. Search for posts by Ron and his ‘Hotrod Hawken’ if you want details.

Bullets from this RCBS mold (purchased mold 44-370-FN from Midway), cast with a 40:1 alloy, weigh in around 400 grains (RCBS spec is 370 grain). Using #9 pound 100% cotton onion skin paper and sized to my GM LRH barrel, I am pushing it to 1400-1500 FPS with 80-90 grains of fff Swiss with a .50 diameter felt wad (.125” thick) over the powder. Will easily hit an 18” steel gong all day at 300 yards.

 

[fleener]

I am pushing just over 1300 ft/sec out of my long range ML with a 530 grain bullet, .45 cal, 86 grains of 2f swiss.

Fleener

 

[Semisane]

This may give you a rough idea.

 

[Idaho Ron]

I have some reloading info on black powder. The trap door rifle is a very weak rifle, barre;l length 22". The only load I could find that used a 405 was 67 grains FFg. the weight was with a scale. the MV was 1202
I have another load for a Sharps High Wall barrel length 28" using a 405 gr bullet with 70 grains by scale. The MV was 1313.

Now my load for my Hot Rod Hawken is a 408 gr paper patched bullet. I am using Pyrodex P 80 gr by volume. The actual weight by the scale is 64.5 gr. I am at 1420 FPS.
Now I am using More by volume but less by the scale. I don't have info on my rifle at 70 gr by volume. But from the numbers I am seeing it would be very, very close.

 

[Idaho Ron]

I use a RCBS 11mm rifle bullet that IdahoRon originally suggested in a setup very similar to what he uses. Search for posts by Ron and his ‘Hotrod Hawken’ if you want details.
Bullets from this RCBS mold (purchased mold 44-370-FN from Midway), cast with a 40:1 alloy, weigh in around 400 grains (RCBS spec is 370 grain). Using #9 pound 100% cotton onion skin paper and sized to my GM LRH barrel, I am pushing it to 1400-1500 FPS with 80-90 grains of fff Swiss with a .50 diameter felt wad (.125” thick) over the powder. Will easily hit an 18” steel gong all day at 300 yards.

That is a very good shooting bullet. And it seems to do really well in most guns.

 

[nkbj]

This is from a TC New Englander that has the barrel relined with a .458" bore diameter.

 

[52Bore]

OP: 45/70 power from my 45

Actually, the 45 (and other conical shooting small bores) were developed long before the 45/70.
Whitworth’s experiments of the early 1850’s proved the long heavy conical 45’s ability at LR more than a decade before the 45/70 was developed.
Many BL developments were adopted from the ML era.
Good luck shooting..

 

[nkbj]

Mavrickbobsr,
If you're looking at getting a .45 rifle, revolver and pistol molds can be a whole lot of fun, too.
A little more brain sweat getting them to shoot as opposed to longer lead but lots of fun plinking and good to practice with. Paper patched .45 semi-wadcutters just act like shorty maxi's.