Re: Experince with .20 cals
20 Tac rules. I have a newly acquired Cooper Phoenix (Model 21). I haven't shot it yet, but the previous owner provided targets and load data when he was testing loads, and it is really impressive. Less than .25 MOA at 100 with 39 Sierra Blitzkings going about 3800 fps, and 32 grain V-Max well over 4000 fps. My barrel is a stainless 1:12 twist 26" heavy varmint. I'll post poics when I get a chance. It currently has a SS 3-9x ffp mil/mil scope (really nice scope - if only they offered a higher mag variable) on top.
If you want more info from small caliber guys, you should really check out saubier.com All they do is small caliber (.14, .15, .17, .19, .20, .22 calibers) and there is a ton of great info on the 20 Tac (as well as about a million other wildcats).
The 20 Tac is really good on coyote well past 300 yards, and p dogs/ground hogs out to around 600+ yards. The round is flat shooting and packs a whollop when it arrives.
20 Tac brass is now available (Lapua), and proper dies are made from Redding, Hornady and at least 1 or 2 others, so forming from .223 is no longer necessary.
You can find ammo in 1 of 2 places (to get you started before working up loads).
Hendershots will make some ammo for $35-$38 dollars a box (about FGMM prices - at least locally), and
Buck Ammo also makes some in boxes of 100 for what seems a better price (~$122 for 100).
By all means take a look at the "major" manufacturer bullets (Hornady, Sierra, Berger, etc), but also look at some of the "boutique" bullets makers who specialize in hand swaged bullets. Most of them are better by all accounts, and not much more expensive (if at all).
No Name Bullets is supposed to be, as one member on the board likes to say (though forget his handle right now), the cat's ass.
Calhoon Bullets are also supposed to be very good.
But definitely go to Saubier.com. They know their small calibers and 20 Tac is a favorite over there. You're sure to get all of the info you could ever desire there.