Thanks for this thread, guys. Just this morning, the transport truck dropped off my new Uberti .50/95. Along with it, I received 40 rounds of loaded Bu.Arms ammo made from .50/90 brass as well as 200 B.A. 510" and .512" bullets. I did not know of the groove size deal, but no problem. This afternoon, I pulled all of the bullets anyway, dumped the 80gr. of what looks like 2f Swiss or perhaps 2f GOEX Ctg. or Enysford - very shiny hard angular BP grains. I loaded them up with some IMR4895 and IMR4198 soft-ball loads with the .512" bullets. With must the calipers, it appears to have a .512" groove diameter, but perhaps tomorrow I'll slug it properly & find it's .513" or .514".
One the subject of moulds, I have an old #515141 Lyman mould. Some books call it a 422gr., others 450gr. as with the Lee mould for the same bullet that I also have. I drilled out the nose of the Lyman mould some time ago and installed a plug making it cast a shorter nosed 420gr. bullet in quite soft alloy, perhaps 30:1. This bullet shoots very well indeed in my original .50/70 Sharps 1859 carbine barrel.(on an Italian action I finished) As original at 450gr., it started opening up at 100yards and were keyholing at 200, due probably to the original barrel's 42" twist. since shortening the bullet, they shoot amazingly well, holding 2 1/2" at 100 meters with the original carbine sights- off bags, of course.
The barrel, still marked 1859, was chambered for a long .50/70 case, actually 1.9", under Army contract in 1867. It would have been called a model 1868, I assume. Good bore, 3 groove.
That's all beside the point, I am now looking forward to shooting some of those bullets. I also have another 60 Jamison cases coming. I also need to start casting & experimenting as I want to use it the end of this month for Whitetails up North.
Thanks again for the thread and suggested loads.
DTS