I have been able to obtain very good accuracy out of my Winchester 1885 (Miroku) in 270 WSM, using reduced loads listed in the Speer manual that push a 130 grain bullet at 2,100 fps, very similar to a 125 grain 30-30 load in energy and velocity.

By very good accuracy, I mean that 1/2" or better groups of five rounds at 100 yards are common. The best group so far, center to center was .317", as close as I have been able to determine.

I will describe one of my loading tricks for discussion. - Have I got a good idea here, or am I full of farina?

What I've been doing is to neck-size my brass with a Hornady neck sizing die - but I only size the first three-quarters of the neck, leaving about 1/10th of an inch of the neck next to the shoulder unsized. - My thinking being that this will aid in keeping the cartridge centered to the bore.

Every third or fourth loading, they get reluctant to chamber so I full-length resize them, and then return to partial neck-sizing after they've been fired.

Does anybody else here working with bottleneck cases do this partial neck-sizing thing? I am curious because I have not read about it anywhere - but it seems to work for me.

Kind regards,
Salvo

I also only partial size neck on the .22 Hornet & .222Rem. & 7mm Mauser. Believing the expanded portion right in front of shoulder angle helps center case in chamber.  I am shooting cast in all of these and use Redding bushing type neck sizing dies.