The Relationship of Center of Gravity and Pressure with Slugs?
This is from another thread on another topic...
Quote:
Originally Posted by
longbow
Now I am wondering... shouldn't center of pressure be behind the CG for drag stabilized slugs and in front for slugs from rifled guns?
From what I've seen of seen of the slow-motion videos, that hasn't been working out very well for the Lee slugs as their center of pressure is definately behind the center of gravity. I think for any projectile to be successful down range, a repeatable MOA of any size, the center of gravity needs to be slightly aft of center as well of the center of pressure. From that, the center of pressure needs to be slightly ahead of the center of gravity.
The problem for most is measuring either value. The math is tough and the only user-friendly software that can do the math, as far as I know, is TMT's Cast Bullet Design. Even that program has problems with a tapered skirt with a hollow base. Same with the actual "key" within the hollow base of the Lee. Still, I think the calculated measurement is very close. The TMT software measures the values from the base of the projectile expressed in a percent of the total bullet length. As a general rule, I like seeing a CG about 47.0 to 48.5% from base, with the CP greater, and within 1% of the calculated CG. This is simply a comparison on my part, the numbers from the drawing against MOA performance downrange.
Quote:
Originally Posted by
longbow
Have you considered round balls? 0.678" RB's in an appropriate shotcup are a good fit. 0.662" RB's in steel shot shotcups are a good fit. and 0.735" RB's are a good fit for bore size. Even 0.690" RB's in thin petal shot cups could work.
I haven't to date as the rules for the hunt specifically state "slugs." I'm not a fan of round balls for hunting, I've shot a bunch of small game with my centerfires, 218 Bee through 38-55 Win, using alloys from pure lead to Lyman #2, and never have I cleanly dispatched game, not once. I am going to pursue round balls through my shotgun shooting this year, just to see how they perform in smooth vs. rifled barrels.
Theoretically, the CG and CP are centered in the round ball. I've always heard to put the sprue cut up front, but what makes sense to me it to put it to the back. That flat represents missing material which would shift the CG slightly aft, leaving the CP at 50%.
Of course, all this is just armchairing. I'm one that likes burning powder even if it doesn't go as planned.:veryconfu