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]

From Nosler manual #6

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.

 

[swift]

In my HVA 1640 6.5x55 AI with a 26'' barrel I reach 2950 Fps with a 139 gr scenar bullet which gives me 63500 PSI .The 123 gr bullet leave the barrel at 3240 fps and the same pressure(I use Wv N560 powder)With a bc of.570 this is a exellent long range load

 

[CapDog]

I shoot a 260AI, which I know is different, but capacities are similar. Out of a 24" barrel I can push 139gr Scenars and 140gr A-max's to 2914fps and 2937fps respectively.

I'm just about to start loading for a Tikka Varmint in 6.5X55. It will be interesting to see how much faster it can be pushed past the mausers I already have.

 

[Jamie6.5]

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?

What platform are you shooting? The original Swede model 96 Mauser?
The debate rages on about how far you can push a factory small ring Mauser action, but in modern rifles the picture changes for the better.
Any time you Ackley a chamber you reduce bolt thrust, which is a good thing when you are looking for max velocity, but how far you want to take a Mdl96 Mauser would be up to you.

More info please.