115s in 6BR

[cmillard]

anyone out there shoot any 115 grain bullets in a 6BR? More specifically in a 1-8" twist? i know some might say that the 1-8 is too slow, but i have shot 90 grain bergers (.224) out of my 18" 1-7" twist ar-15 with very good luck. i am thinking about ordering a batch of JLK 115s. if you have had some luck, what did your load consist of?

thanks

 

[Yellow11]

It is all a matter of degrees - either cross your fingers and close both eyes or go for maximum accuracy by following the logic of Don Miller's formula.

You should be aiming for a gyroscopic stability factor of 1.4, which means a 7-7.5 twist... anything else will be a compromise.

Approach your problem from the opposite direction and pick a bullet whose length and weight will give you a SG that matches your barrel.

 

[cmillard]

i punched some data into my Knight's BulletFlight software on my iPOD. i got the specs off the JLK website on their 115 grain .243 bullet. bullet length--1.385, and put in various environmental conditions, as well as 8" twist. program showed that at 2750 fps, the bullet would not be stable. 3000+ fps was needed for the bullet to be stable out of an 8" twist. although the JLK website said that the optimal twist for the 115 is an 8". i guess i shall place some on order anyhow and my barrel will decide if they shoot. now, just need to figure out the optimal powder......hmmm.

 

[Steve Blair]

Temperature affects stability more than velocity. Make sure that you evaluate stability at the lowest temp you will encounter. More of a consideration for hunters than target shooters. Not many of us enjoy shooting for group while shivering.

Reloder 17 is likely to give good velocity behind the 115s. I have used it successfully with Sierra 107s where it is about as slow as the 6BR can handle.

 

[TonyR]

Cole
My 6mm BR shot nice round holes to 1000 yards with those bullets out of a 31 inch 1:8 Krieger. I was able to get what I believe was an honest 2820 fps based on comeups at different distances. VV N540 with CCI450s. That was not a maximum load. Just where my rifle tuned. I never shot them below 50 degrees at sea level so I can't say what would happen if it got cold. I never pursued it further because the velocity decrease seemed to offset the BC increase versus the 105 VLD. if you want a heavier bullet for some reason other than wind drift, they certainly shot as well as the 105s did for me, just no better as far as I could see. It is certainly worth a try if your throat is long enough. My rifle was chambered for the 107 SMK. The setting on my bullet seater was the same for the Berger 108 BT off the lands as it was for the 115 VLD jammed 0.010-0.015 inches and that kept the bullet out of the donut area.
Good luck with your project.

 

[Laurie]

British F-Class shooter John Carmichael used a 6BR RPA with 32" 1-8" twist Lothar-Walther barrel in both GB F-Class Assoc and international events back in 2006 / 7. His load was the 115gn Sierra / DTAC over a case-full of Viht N550 running serious pressures and velocities, and this stabilised OK including in our dense winter Bisley atmosphere.

The DTAC is a relatively short bullet for its weight, so the Berger or JLK VLD might push the twist rate too far for comfort, especially at slightly lower MVs. How did John do with the BR? He got top 10 places, top half-dozen on occasions, but adopted 7mmWSM in 2008 to stay competitive, the cartridge switch alone moving him into the top three on several occasions.

Laurie,
York, England

 

[Obtunded]

I played with them in an 8" twist 28" krieger and got a 6" group of big ragged holes at 200. Using 30 grains of anemic Varget and doing 2775-ish. I gave up there.

 

[Neale]

i loaded up 5 115 dtacs for my 6br just to try, and they shot fine. i have a 30" krieger 1-8" tw chambered in 6br norma .272 nk and throated for 105-107's i jumped em like i do 107's which is .020" and still the 30gr of varget i use for those and they shot .421" ctc 5 shots at 100y. didnt chrono but i konw the 107 smk's are about 2850 fps. it was about 75 deg.