6br barrles 7.5tw vs 8tw

[eddief]

Going to build a straight 6br for 105 to 107 bullets

I already have a Bartlein 7.5tw MTU contour blank and was wondering if it would be better to off it and get a 8tw...thoughts??

Thanks,
Eddie

 

[cmillard]

i would keep it. an extra half twist wont change things--at least shouldn't. if you keep it, you might as well try the heavier 6mm bullets. the 115 berger, 115 JLK or the Tubb bullet. these bullets might be a bit much for the regular 6BR, but it doesn't hurt to try. i am going to give these bullets a try in my 6BR 8"twist 5R krieger.

 

[jr600yd]

Naw, it won't shoot for beans........Since your a nice guy I'll buy that no good 7.5 twist tomato stake from you.

Good shooting
Jim

 

[Yellow11]

Stick with the 7.5" twist, as it will give you a SG that will work with the DTAC 115gr (at 3000 fps) and will give you a SG above the magical 1.4 for the 105gr bullets.

 

[tclaunch]

eddie, for those weights, I`d opt for a 8.5" t. Save the 7.5" for a Dasher/BRX/6x47L and the DTAC`s

 

[Steve Blair]

I shoot 115 Berger VLDs from a 30", 7.5 twist barrel in 6BR at 2870. They shoot very well. They perform a little better than Sierra 107s at 3000.

 

[eddief]

Great info and thanks.

sleepygator,

If you don't mind me asking, how hard are you running the brass with the 115's

Thanks,
Eddie

 

[Bob3700]

The 7.5T will shoot the 107 wt bullets just fine. No accuracy loss.

I don't believe that the BR case is going to be a candidate for the 115gr bullets. You just don't have enough boiler room to take advantage of the heavier bullet. Your velocity will drop down to the point where the 107 gr bullets have the advantage.

If you want to shoot 115 gr bullets, get a bigger cartridge. The BR is great when used for it's intended purpose, but don't try to make it something it is not.

The BRX and Dasher will extend it's range some but overall the BRs are at their best at 600 yds.

Just my .02.

Bob

 

[Steve Blair]

Eddie,

In Lapua brass with a fired volume of 39.0 H2O and Wolf KVB-5.56M, velocity @ 15' with Kurzzeit chrono:

32.1 g RL17, Berger 115 Moly seated 2.425 (-.017) - averages 2870
33.2 g RL17, Sierra 107 Moly seated 2.385 (+.010) - averages 3006

Both loads listed above are near maximum in my Savage 12F. Reduce by at least 10% and increment by 1%. RL17 is temperature sensitive. In summer temps (90-100f), I reduce the 107 load to 32.5-32.8. The above loads were developed in 65-75f. It was 78f at the range today, 8 January.

 

[eddief]

Thanks sleepygator.

I'll trade you weather, it's 20*F with about 6" on the ground.

Eddie

 

[Steve Blair]

I also should have added that RL17 does not provide best ES/SD until pressure is near max.

There is some seriously cold weather happening right now. It must be global warming.

 

[cmillard]

there we have it. it has been said that re-17 will not work in a 6BR, and that a 115 grain bullet will not work. Well, they were both used together with apparently good results. I might give it a try out of my 8" twist.

 

[Steve Blair]

Cole,

I have not shot the 115 from an 8", it might work. My 8" twist is a Savage factory barrel and, although it shoots well, it cannot match the 7.5" Bartlein. The 107 Sierra shoots very well from the factory barrel.

Steve