What boolit for a Sharps 45-70?

[4570mike]

Last year I purchased a Chiappa Creedmoor Sharps Rifle in 45-70. The rifle looks to be very well made and I have had no problems with it shooting. What has been a problem is accuracy. I haven't had time to do some of my own casting, so I bought some 300gr. and 340gr. (.459) Hunters Supply Cast Bullets; I wanted heaver, but this was all I could find at the time. I slugged the bore, and it measures .458, so I was confident the diameter was okay. After trying several powders (all smokeless) and numerous loads, I still can't get anything like a reasonable group at 100yds. Some loads on an SR-1 target would barely stay in the rings; the best I had was maybe a 6" group. I have tried light loads and heavy loads mostly with IMR 4198 and IMR 3031.
The rifling twist for this gun is 1 in 18". I noticed that the rate of twist for some other 45-70 rifles was 1 in 24". I'm wondering if the twist is too fast for the lighter boolits?
Anyone out there have any experience with one of these rifles and suggestions for accurate loads?
Thanks,
Mike.

[Doc Highwall]

What are you going to use the rifle for and at what distance? Do you want just smokeless powder loads or black powder loads as well?

[John Allen]

I like the 405 grain to 535 grain bullets in mine.

[sharpsguy]

With the 1-18 twist you will need a bullet in the weight range of 480 to 520 grains for the rifle to shoot really well. My 1-18 twist guns will not shoot 400 grain and lighter bullets worth a darn.

[detox]

The RCBS 82085 45-500-bps shoots verygood in my Browning 1885 BPCR. I use 20/1 alloy with SPG lube. It will shoot 1 inch groups @ 100 yards with blackpowder. I cannot remember what it shot using smokeless, but i am sure it was not bad.
http://www.midwayusa.com/product/317308/rcbs-1-cavity-bullet-mold-45-500-bps-45-caliber-black-powder-silhouette-458-diameter-500-grain-flat-nose

[4570mike]

Thanks. I suspected the lighter ones might be getting over stabilized. I ordered some 400gr. lead boolits; I really need to get off my duff and do some casting; I have two molds that should do fine.
Thanks again, Mike.

[Clay M]

I guess it depends on what you call shooting.My Shiolh Sharps Saddle rifle will put five shots in 1.25" at 100yds with a load of 31.5 grs of AA 5744 and the RCBS 400gr GC bullet. The old lyman 457125 is a great mold for the money and will generally shoot well in most of the Sharps rifles.

[Ron in PA]

I use Lyman 457124 and RCBS 405 GC . Same gun i have, shoots well.