I like the 22-243 Middlested. It can be rechambered from any 22-250.
http://www.reloadbench.com/cartridges/w22243m.htmlHere is ACKLEY IMPROVED CARTRIDGE COMPARISONS
Dale
Factory Cartridge Bullet(grs)Factory Velocity(fps)Ackley Velocity(fps)%Increase
1 25-35 WCF 117 2230 2800 25.6
2 30-40 Krag 180 2430 2900 19.3
3 250 Savage 100 2820 3300 17.0
4 6.5x55 Swedish 140 2550 2900 13.7
5 30-30 WCF 150 2390 2700 12.9
6 7x57mm Mauser 145 2660 3000 12.8
7 300 H&H 180 2880 3200 11.1
8 257 Roberts 117 2650 2900 9.4
9 270 Win. 150 2850 3100 8.8
10 25-06 Rem. 100 3230 3500 8.4
11 375 H&H 300 2530 2740 8.3
12 243 Win. 100 2960 3200 8.1
13 270 Win. 130 3060 3300 7.8
14 280 Rem. 140 3000 3230 7.7
15 30-06 Springfield 180 2700 2900 7.4
16 30-06 Springfield 150 2910 3100 6.5
17 219 Zipper 55 3300 3500 6.0
18 6mm Rem. 75 3400 3600 5.9
19 220 Swift 50 3870 4100 5.9
20 7mm-08 Rem. 140 2860 3030 5.9
21 375 H&H 270 2690 2830 5.2
22 22-250 Rem. 55 3680 3850 4.6