I have a .221 rifle that I had made up on a Remington 600. I had McGowen rebarrel it with a medium-heavy 1-14 twist 21" barrel.
I had trouble picking a barrel length, so I just doubled the 10.5" length of the XP-100. Pretty scientific, huh?
It made into a cute rifle after I restocked it. It looks kinda like a 7/8 scale African rifle.
Anyway, here are some of the better loads. They aren't as small of groups as the ones Steve Timm shot while at Kimber, but I only have a Leupold 1-4x scope mounted.
1- 12.0 grains of Accurate arms #9, 50 grain Sierra Blitz, Federal 200 primer. 7/8"@2622fps.
1A-11.5 grains of the same powder, all other components unchanged brought group size down to 7/16 to 1/2 inch. Velocity 2540 fps.
2- 21.0 grains of WC846 (surplus powder), 50 grain Sierra Blitz, Fed 200. 15/16"@2848fps.
3- 17.0 grains of IMR 4198, 50 grain Remington softpoint, Rem 7 1/2 primer. 1"@2835fps.
4- 14.4 grains of IMR 4227, 52 grain Speer HP,Rem 7 1/2 primer. 15/16"@2793fps.
None of these are earth-shaking groups, but not bad for a 4x scope. They really aren't much different from my XP-100. But the rifle is so much easier to shoot, and almost as handy.
Please notice the changes brought about in loads 1 and 1A by varying the powder charge by .5 grain. That goes to show how sensitive the small case is to change. It ran pretty typical regardless of powder used.
I see by my records here, that the last time I did any work with that rifle was in June of 1993. Hmm, maybe it's time for some more.