12 twist will stabalize the following:

60g Sierra
70g sierra, 70g Hornady Sp
75g Sierra
75g Hornady's
80g Sierra Blitz(great coyote bullet)
85g Sierra
90g Speer spt

The 90g speer is great on deer and antelope, make no mistake about that fact!

You will get great accuracy with win and rem brass, if groups in the 2's and 3's will make you happy.

70's at 3400 will be no issue at all if your barrel is at least 24" long, I got 3550 out of a 26" with tiny groups.

Someone asked the question as to why go a 6/250 vs 243, you get almost the exact same velocity with 10g less powder....that's a bunch. H4895 has very low pressure and may give more barrel life than H335...you should expect 4500 rounds out of a barrel if you have the chamber cut with minimal freebore, all that extra freebore just robs you of barrel life...bullets only will jump so far before they get started crooked in the barrel.

I killed hundreds of coyotes with the 60g Sierra out of a 6 Rem and 243 at velocities of 3750-3900 fps and the 6/250 will spit them out at 3850 with ease with 38.5g of H335(your rifle may like a different load).

6/250 is a great cartridge and you will love it, just dont like some idiot throat it long.

If you can stand the difference, then consider the 6/250 AI, one of the best cartridges for a short action. I shot the 70's at 3800 out of a 28" barrel. This cartridge feeds from the magazine with ease as it looks like a long 6 BR, in fact the 6.5x47 Laupa is just a tiny bit shorter than the 6/250 AI...that tell you anything?

If you are a hunter, then I would not screw around with Lapua brass, I got unbelievable groups with Rem brass along with PMC 22/250.

Pac Nor will do a whale of a job for you with one of their super match barrels throated short, I had my chambers cut with zero freebore and a 1 1/2* leade angle on both the std and AI chambers...unreal barrel life with tiny groups first time to the rifle range.

If all you ever wanted to shoot was the 70g or 68g Bergers, then I would go a 13" twist, there are some VLD bullets out there in the 70g range that will demand the 12" twist.

I have been playing with a 6.5x47 Lapua made from Rem 22/250 cases and accuracy is outstanding at 200 yards, and this cartridge will feed from the magazine as well, you may ruminate on this cartridge as well as the 6x47 formed from 22/250 brass. I have got 15 firings on the Rem brass so far with top end loads, one full length sizing. The 6x47 Laupa is basically a shortened 6/250 AI...wonder why no one has ever pointed this out?

I formed the 6.5x47 Lapua from 22/250 brass by necking up the 22/250 brass then fireforming the brass in the chamber with 9.0g of Bullseye and the case topped off with cream of wheat, case was 95% fire formed. I could not get Lapua brass in this caliber, hence the use of 22/250 brass.

Hope all of this does not make your head explode.