Case sizing

[Mike0904]

I'v had success with just sizing half way with a full length sizer using BP in my RB 45/70
But now to keep on shooting it I'v had to start using smokeless and keeping muzzle velocity the same most powders dont burn complete. Since I dont have a case mouth sizer would I get better results doing the full length size and good crimp with smokeless ?
And also would a case mouth sizer (when I can afford it) be a good idea ?

[BerdanIII]

I'm definitely not an expert on big, straight cases, but what powder(s) are you using? A powder 'way too slow for the application would leave unburned grains (possibly a lot of unburned grains) of powder behind. Also, a light load of an otherwise suitable powder will do the same thing. XMP5744, even though designed for reduced loads in big cases, often leaves unburned powder in the bore. In proper loads, SR4759 leaves much less debris (in bottlenecked cases, anyway) in my experience. The real test to me would be accuracy: if the loads are accurate, a little crud in the bore wouldn't bother me unless it interferes with functioning.

I don't see that the method of sizing is the problem here.

As for case mouth sizing, if I remember correctly, Mathews mentioned using a .45 ACP sizer (minus the decapping assembly) for case mouths in the .45-70. I'll double-check this to make sure. Whether or not this would work for you depends on the bullet diameter you must use in your rifle. You might be able to find a used .45 ACP die set at a gunshow. Around here, used die sets are pretty cheap.

Edit: I don't remember correctly; Matthews (not "Mathews") mentions a shooter who uses a .45 ACP taper crimp die to remove the case mouth flare from his cartridges.

[Shooter]

The less you work your brass the longer it lasts. In my single shots I often do not size at all. I seat the boolit, and crimp.
Breech seating solves all problems.

[Mike0904]

Well I sized 10 with the full length and a crimp, doing 10 more using a taper crimp to just take the bell out. I guess I will see what works best for me. BerdanIII and Shooter I did pick up a couple things from youse. I have Matthews book I just dont "read" well, will dive into it more.

[Mike0904]

Testing done on sat went well. The sized uncrimped had best groups . All had 3 shots touching each other but, the best had 5 shots inside 2". Did 2 sets of 5 each. I think it was more about the powder I was using than the crimp.