You might get 600 FPE at 3500 psi using an 18" barrel with a .58 cal.... if you do everything right.... It will, of course be VERY noisy, because with that short a barrel the residual muzzle pressure will be very high....Bob
You asked about 300 gr. @ 950 fps, which is 600 FPE.... I didn't think it was necessary to repeat that, but yes you should be able to do that in .58 cal with an 18" barrel at 3500 psi.... Bob
I am well aware that using a heavy bullet at low velocity is a good way to "inflate" FPE numbers.... My "lofty goal" predictions are always done with a bullet weight of 1/2 the FPE, so that is at 950 fps.... You're pretty new around here, so you wouldn't have known that.... Ö. Oh, and welcome, BTW.... I think the idea of a short barreled 12 ga. is a cool way to get lots of FPE.... I am just trying to show you it's not the only answer.... and realize that quieting a 600 FPE beast with a short barrel is going to be a TALL (or at least "long") order.... Bob
Has anyone ever set up a .58 with a 500gr Minie ball? That might be interesting.
A roundball in .73 weights around 500gr and have a bc about .10If you have bullet in cal .73 that weights 300gr it would be way shorter then wide, maybe around .35 inch long .It will of course work but you BC and long range performance will not be the best.If you raise the pressure to 4500psi then you could even make you goal in .50cal for little better BC.Accurate molds have mold close to 300gr in 20ga anything lighter would probably be needed to be custom made.Will this be a bullpup or a pistol? It will be awesome power in that compact of package! Quote from: Doug Wall on January 29, 2019, 05:01:09 PMHas anyone ever set up a .58 with a 500gr Minie ball? That might be interesting.What a great idea! convert an old reproduction muzzleloader to PCP
Hey Fielding, originally from Maryland myself...you have some ambitious goals set but I think all can be met within reason and if necessary some compromise. Attached are some approximations I ran for a .58 cal with the parameters shown. Look forward to seeing if you commit to the build!