wildworks said:
After cousulting with smi about the max pressures for the gun I found out that the Green monster was not anywhere near its potential. SmI tested the gun to 90 gr 3031
I started to go up from 75 gr 3031 @ 2200fps
I ended up going up to 90 gr that is where the pressure started to show in the primer not blown just starting to swell a little this is the amazing thing!
375 gr rbbt Wildcat ML bullet @ 2563 fps!!!!!!!!!!
the load i backed down to was 88 gr. 3031 no pressure signs and still running for 3 shots 2509 2516 2511 fps so not much spread!
now its off to the range to see what its going to do at Long range my sofware shows only 15.2 MOA @ 500yrds !
i will post results
If one were to explore the maximum power available in a smokeless muzzle loader the results are astounding.
I hesitate to give these loads because the actions of the beginner are generally to shoot too heavy bullet with too fast powder and things go sour very fast when one has little conception of how to make power and still remain in the pressure constraints of the rifle.
So I began this reply by telling each and every one if you load your rifle with the amount of powder in these loads and think smokeless is smokeless there are all sorts of things that can happen and none of them are good. On the other hand all of the loads I refer to have shot out of many types of rifle many of which do not have half the strength of the 10ML or SMI with perfectly safe results. BUT YOU HAVE TO USE THE CORRECT POWDER IN THE CORRECT AMOUNT!
I make no claims for your safety except I have shot most (but not all) of these loads from my own stock (no modifications) 10ML. And they proved safe in every aspect. Some of the loads were shot from my 50-140 but that rifles maximum pressure is well below the 10MLs regular shooting level.
Let me start with a 50-140 load. One of my favorites is 105 grains of AA 4350 under a 550 grain flat nosed bullet. At 2184fps this load makes over 5800fpe (more than a 458 Winchester Mag) at less than 28,000psi pressure. The Accurate Arms data in fact gives an exact pressure of 27,500psi.
The Sharps rifle this load was shot in had a 30" barrel and even allowing for some dead length for the breech plug a 36" barrel should beat this speed by at least 100fps which would break 6300fpe at the same pressure. Translating that to your 387 grain bullet (add the sabot) thats 2600fps at the 5800fpe level and 27,500psi without allowing for the additional barrel length.
Of course the load can't be directly translated because of the lighter weight bullet you'd want to use a slightly faster powder than AA4350 to achieve equal results. Also you'd want to shoot a little more pressure for consistency reasons. The low pressure loads for the 50-140 require a firmly crimped bullet for results and one cannot crimp a muzzle loader load. However a slightly higher maximum pressure and faster powder have the same effect.
Let's take a look at the 505 Gibbs. This old low pressure cartridge also shoots to astounding power. At a pressure limit of 35,000CUP (I won't go into CUP versus psi but I'll say 35,000CUP is less than 40,000psi) this old boy packs a wallop. The wallop was felt at both ends that's the reason smaller calibers became popular even for monstrous sized game.
Lots of Gibbs loads show a 525 grain bullet making 2300+fps (6100fpe) out of a barrel nowhere near 30" long. So raising the pressure to this level ought to be pretty interesting out of your 36" barrel.
Some loads for the Gibbs show a 600 grain bullet at 2300fps. This load was not measured for pressure so could exceed 35,000CUP but not by much. That's 7000fpe but I don't even think the most adventurous soul would really want to go there. OUCH.
When Bad Bull came out with their load showing a 300 grain bullet to 2900fps (a mere 5600fpe) out of a 45 caliber rifle some oohed and ahhed and wondered if the rifle had to be designed to shoot to at 100,000psi. I realized a muzzle loader has no case and the pressure was dependent on how much powder was burned to get to the speed. What people didn't realize was the Bad Bull load was not very high pressures.
Now following that line of thought the 50 caliber barrel has 20% greater volume than the Bad Bull's 45 caliber. Even if you allow for the fact that the pressure in the 50 caliber barrel is less the 50 caliber barrel (same length) will shoot the Bad Bull so far into the weeds as to make a search necessary.
My bottom line to you is 2500fps with a 387 grain bullet from a 36" 50 caliber barrel capable of 40,000psi pressure is a rather mild load.