what caliber is a 6.5mm bullet in a 308 win case?

3000'sec with 140s is a bit of a stretch even for the AI version of the 260. You're in 6.5x284 territory at that point.

Any of the calibers that are based on the 308 case are great but if you want 3k'sec plus... You need lighter 26 cal bullets than 140s. You can drive 30 cal 155 grain bullets a he!! of a lot faster in a 308 case than a 26 cal 140 grain bullet in the 308 case, up to including 3000'sec. For 500 yard deer and paper, the 260/140 combo is fine. That said, the 708 running 162 amaxs or 168 vlds works well too as does the 308 running 185, 190 vlds at 2650-2700+'/sec or 208/210 which can be ran up to 2600-2650 in 26" barrels.

Run the numbers against the 260, 708 and 308 using 140, 162 and 208 amaxs out to 500 yards and there is not enough difference to sweat it. Some will drop less than others, some will drift less than others and others will hit harder than others. All that said, using the heavy for caliber bullets, the windage between the three is about identical. The major differences will be energy.

Do you want minimal recoil or barrel longevity?

When one decides to call 500 yards or less for deer and paper, the less critical cartridge/caliber/bullet choices become. When one adds another 500 yards to the mix, it isn't so simple. Just remember, equal case designs utilizing different calibers, the larger calibers will drive equal bullet weight as the smaller calibers faster but the smaller caliber will have higher BCs for equal weight but the larger calibers will have higher BC potential with more mass available. With this balance, equal cases in different calibers generally will have equal or close to equal windage potential. The recoil, energy, trajectory and barrel life between the three will be vastly different. You'll have to pick which qualities are most important to you.

For what you're looking for, the 708 is a great balance. Less recoil than the 308, better energy than the 260.
 
3000'sec with 140s is a bit of a stretch even for the AI version of the 260. You're in 6.5x284 territory at that point.

For what you're looking for, the 708 is a great balance. Less recoil than the 308, better energy than the 260.

+1

The 7/08 can exceed 3100 with the 120s and using Varget get 3000+ with a 140 grain bullet.

I have used it past 600 yards on deer with 100% success.

David Tub used it for years to win at Camp Perry in the National Hi Power championship out to 1000
yards. so I would have to say the 7/08 was very capable.

If you want more velocity, the 7/08x40 will exceed 3150 with 140 grain bullets with a short action cartridge.

J E CUSTOM
 
I thought you might appreciate this comparison: I shoot the same 140VLD Berger in both 6.5 Creedmoor (25.5 inch barrel, varmint contour) and 6.5/284Norma (26 inch heavy varmint). The loads I settled on for best accuracy run 2735fps in the Creed and 2870fps in the Norma. Each can go faster, I saw 2850 out of the smaller case, and had the 6.5/284 up to 3050 using Retumbo, but the groups were getting loose at those speeds. The 6.5/284 is built on a long action savage (111) because those long VLDs usually don't fit in the magazine of a short bolt action without stuffing them WAY deep into the case. At 1000ft altitude/55degrees, the 6.5/284 carries 1000ft/lb to 800 yards, with a drop of 17.3moa and 10mph wind drift of 4.6moa. The little Creedmoor carries 900ft/lb with a drop of 19.2moa and wind of 5.0 moa to the same distance (200yd zero). For the purpose you described in your original question, either cartridge will do what you want, but the Creedmoor will be cheaper to feed and the barrel will last a lot longer especially compared to the Norma run at full throttle. Either way you are gonna have fun!
 
you want 2900fps from a 6.5 bore cartridge using a 140 grain bullet. The .257AI necked to 6.5 is your answer. It easy to do, and cases can be formed from 6mm, .257 Roberts or simply 6.5x57 brass. Kiff sells the reamer ground to headspace off of .257 brass necked up to 6.5 caliber. The round is capable of close to 3000fps. Of course the 6.5x55AI is just 150fps slower with the same bullet.
gary
 
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