"Ken, are there any over bore capacity cartridges that you are aware of for normal speed rifle powders? Such as IMR 4064, IMR 3031, powders within that range more or less."
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<br>Yes, the world's full of cartridges that are over bore capacity for the powders you mention, including those that aren't over bore capacity in the generic sense that there's NO powder that they can safely fire by the caseful.
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<br>Just for example, I plugged IMR-3031 into the computer to see what pressure a caseful of it would churn-up in my .220 Howell with an 80-grain Sierra -- over 113,000 lb/sq in.!
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<br>I should add that the optimum powder for any case depends on (a) the net capacity of the case, between the web and the base of the seated bullet, (b) the maximum average peak operating pressure desired, and (c) the weight of the bullet. In a given case, for example, the heavier bullets would generally call for a somewhat slower powder -- and the lighter bullets a somewhat faster one. How easily the bullet can be pushed down the bore -- or how stubbornly its mass resists propulsion -- affects how the powder behaves.
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<br>Since I designed my .220 Howell strictly for 75- to 80-grain (and heavier) bullets, I centered the design on IMR-7828 -- and sure enough, IMR-7828 is one of the two or three best powders for it WITH THESE BULLETS. I'm not interested in using anything lighter in it (yet), so I haven't considered anything lighter for it. It may NOT be over bore capacity for IMR-4831 or IMR-4350 or even something a little quicker, with the lightest .224 bullets. I suspect that it isn't, but I just haven't looked into that question at all.
