what is possible?

[fastnflat1]

wanting to push a 75gr vmax out of a 6mm AI as fast as possible. dont care about barrel life as barrels are cheap fun!! hopefully can get to at least 3900 fps. planning on using a krieger 14 twist 4groove but do you think its possible to stabilize the 75gr vmax in a 15 twist running in the 3900-4000 fps range? what about a gain twist barrel? would they allow more powder to achieve more velocity due to a slower pressure curve? building this for a super flat and fast varmint destroyer!!! any comments and ideas welcome.

 

[40X Guy]

As Dave mentioned, read the article he linked to. Richard has built dozens of 6AI's. But he is now retired and I believe back in Canada. Tommy Shurley took over his business and he can help or can direct you to Richard. He's at 501-691-5500. I have 2 6AI's but both are 8 twist set up for LR BR. If I were planning a 6AI set up for 75 grainers, I would probably go with a 12 twist and at least a 28 inch barrel throated for the bullet you want to use. One serious cartridge!

Frank

 

[fastnflat1]

thx for the suggests guys. I had previously read the article of richard franklins and that is what really hooked me on the combo im wanting to go with. hey 40x guy I have to ask why you suggest the 12 twist? I realize I could shoot the 87s if wanted to but im building for maximum velocity and figured if the 14 or 15 twist doesnt stabilize the 75s then I ll step down to the 65s and crank up a little more velocity. some people think us speed freaks are crazy and thats fine, everyone is entitled to his own. I have a 20 dasher and 20BR running 39SBKs at 4050fps and am goin to build a rig to run a heavier varmint bullet with the near exact trajectory out to 1000yds so I only have to memorize one dope that works for all three rifles.
thx for listening.

 

[40X Guy]

I hear you fastnflat1 as far as speed freaks go. I don't care one iota about barrel life either. I have a 28 inch heavy barrel Swift on a Winchester action that throws a 55 BT at 4,031FPS, thats the node it likes and its mild with 42.5 grains of H414, also in my speed stable is a .220 Weatherby Rocket with 29 inch 12 twist barrel on 40X action that I am looking to throw same bullet at 42-4300. But I digress, as far as a 12 twist vs. 14 twist in a 6AI, the 12 twist will give you a tad more bullet selection to play with, and one needs a good combo of twist rate and bullet weight to really get out there, but you would be fine with the 14 and 75 V-Max. Just make sure you get reamer set up for a no turn neck with Winchester brass with around .002-.003 neck clearance. Which is going to be around .272 neck. And have reamer built to specs for the bullet you want as far as freebore. Or you can neck down Norma 7X57 Mauser brass and neck turn to fit the .272 chamber which is what I did. I feel the .272 neck is optimum for this cartridge and will give you more brass selection as well.

Frank

 

[MarkS]

fastnflat1
I am with 40X on the 12 tw or 10tw. If you built a gun around one bullet, and it does not like that bullet, then you are screwed. I did this on my first 10tw. I had 2 10tw and one 14 tw. The 14 shot the very good with the 70gr Sierria Blitzking, running 3950 f/s. The 15wt would be on the edge for the 75 vmax.


Mark Schronce