6.5X55 and AI

[6.5user]

I currently shoot a 6.5x55 Swede, and yes I handload it. With 100gr Sierra varmint bullets I get over 3000fps and groups under .2" at 100 yds, 140gr Sierra soft points give me consistent 1.25" at 200 yds. I haven't confirmed the velocity on the 140's yet. My point of this thread is twofold, 1) how much performance increase could I expect by rechambering for the AI version and 2)any ballistics program I have run puts my energy below 1000 ft/lb around the 6-700 yd mark, so what would you consider to be max for this cartridge in either standard or improved?

[Varminator 911]

Nosler #6 shows ballistics for both the 257 Roberts and the 257AI. The Roberts case is similiar to the 6.5x55. Shoulder diameter on the Roberts is 0.429 std vs 0.455AI. Shoulder diameter on the 6.5 is 0.435. So if the AI 6.5 were blown out to 0.455 there would be a little less improvement than on the Roberts. But I'm not aware of what the 6.5AI shoulder would be.

Anyway the Roberts AI shows max vel with 120gn at 2972 vs 2810fps with the standard both in 24 inch tubes. So you might expect 100 to 150 fps increase with a 140 gn bullet in the 6.5 AI if this example is in the ballpark. Using a 140 gn bullet with the highest possible BC would help more at long range than the AI. But combining both could add 200 yds or more to your max range IMO.

Nosler shows a max velocity of 2790fps for a 140 gn bullet with the standard 6.5x55 in a 23 inch barrel. That vel is from 52gn of H1000. Starting load is 2590fps at 48gn. If the 6.5AI could make 2900fps that won't be far from the 6.5x284 which Nosler shows at 2953fps max in a 26 inch tube. The 6.5x284 is a great long range rig it's just a matter of how far that 140 gn pill will be effective on what you want to shoot.

I consider my 7mm 08AI to be a 700 yd rig on deer size game. It's in the same ballpark as what you are talking about.