Re: 20 practical?
I have witnessed the killing power of the .20 caliber first hand - My father-in-law shot a coyote with his .20 BR at 300 yards low in the hind leg and it died instantly, after we skinned it we found than it had blood shot clear into it's chest cavity - I believe the terminal shock that a 32- 36 gr .20 cal bullet traveling 4200-4500 fps is more than any coyote can take. This is something that the .224 bullet just does not do.
As for a larger caliber, I shoot a 6.8 SPC and it also is very effective on coyotes, but it costs alot more to shoot if you were starting from scatch. The .20 practical is just that, practical.....I say go for it!