Looking for alittle input guys, I have a Stainless barrel blank in 6mm, with a 12 twist, 26" long, 1.125 entire diameter. Would like to build something for punching paper, longest range here is 300 yard. Which of the following calibers would you choose and why.
6mm Rem BR, 6mm PPC, 6mm-284, 6mm Rem, 6x47, 240 Wby, 243 Win, I reload so finding ammo will not be a problem. I have a short and long action to choose from for the build.
Any input will be very helpful

Thanks
Bill

Your greatest happiness and satisfaction will be found using a 6 Rem BR. I say this based on the twist, and the intended ranges you plan to shoot. The longer tube will be very fast and the larger bores not as accurate. IMHO of course! Good shooting!

PS: On the long action I'd have to build a 6.5/06.

I would go with the 6 BR, plennty of powder capacity for the 300 yard, 12 twist combination, and not quite as much powder burned as the 243 6/284 etc.

With that twist you will be limited to lighter bullets, about 75 gr or less.

Here is another vote for the 6mm BR. The 1x12 twist should work well wit 85grainers and less. Punching paper is great with 65 to 68 grainers.