I recently acquired an old Superior (Ross Sherman) LV/HV BR rifle. After some research, it appears it once belonged to Becky Sinclair in the early 1980's. When I got it, it had an unknown barrel chambered by Bib's Machine in CO in 6x50. I kept asking myself "What is it"? So it became a 6x50 Whatsit in my mind. After some research I learned it was likely a 6mm neck up from a 5,6x50RWS Mag case. @DaveTooley first lent me a single case to confirm my suspicions, then sold me 120 cases when it appeared the case was the proper fit. I located a used set of dies here on AS. I sent the brass to @MrMajestic who annealed them for me.
Yesterday I put together twelve rounds to test.
I used the FL RCBS dies and a tapered button from Huntington to neck up. A Sinclair mandrel die followed, and I could feel a donut at the shoulder. I turned the brass to .011 and went into the edge of the shoulder to get rid of the donut. (Several test fits with 68 grain Rubrights without cutting into the junction resulted in a NO GO, so I went ahead and turned to the shoulder, which allowed any bullet to fit. ) I only did twelve to start with, as the cases are pricey.
I stole some medium loads from 6x47 load data and settled on trying 26 grains of H322 and a Fed GM, under a Cheek 66 grain FB.
At the range I wanted to accomplish three things: Shoot safely, get on paper, see how the brass fared.
I was very pleasantly surprised as I accomplished that, and more. I did not have flags, but it was a calm day. However I was shooting over snow with sharp sun, and mirage was causing the target to move all around.
When I seated the bullets I had tested the fit in the rifle at home. Four chambered very easily, no resistance. Another 8 had varied resistance, making me realize that I had not completely dealt with the donut. Hey, I am new at this! I used two to get on paper, reserving ten for group, "scientifically" separated into "easy" and "not easy" piles.
I bore sighted it with two rounds, and went to target at 100. The results are below. The small target are the cases that fit easily.
I have deduced that:
I think it is going to shoot
I need to deal with brass differences
I will stick with those Cheek bullets
and lastly, the rifle is no longer a Whatsit, but I have christened it the 6x50 Mo'Better, since it be Mo Better than a 6x47, if only 3mm.
Fun little rifle with some history behind it that I did not know until I bought it. I think I will keep it as a 6mm until this brass quits.
I posted photos at Accurate Shooter, in the small caliber thread, 17, 20, 22's...