whats the heaviest bullet for a 12 twist 6br?

[pdog06]

I just got a 12twist(23" varmint barrel) 6br and am curious how heavy a bullet it will take. Gonna be mostly a varmint gun, with some range work.

I have a bunch of 87gr v-max that I use as a varmint load in my 8twist 6br and didnt know if the 12t would stabilize them or not?

I did a search and didnt find much.

Any info is greatly appreciated.

thanks,
mike

 

[Steve Blair]

Gunamonth is probably right about the 80 Berger MV. Bullet length is the problem and the flat base Berger is relatively short for 80 grains. Look through bullet makers' catalogs for flat base, exposed lead bullets like the Sierra 85 grains spire point (1520) or the Hornady 100 grain round nose (2455). Both are marginal but might work in your rifle. Rotational speed and form factor are the critical points regarding gyroscopic stability. The most important influences to bullet gyroscopic stability are, in descending importance:

Form factor (shape and mass distribution)
Barrel twist
Air density (temperature and altitude)
Bullet velocity

This article gives a good overview of a complicated subject. Some folks have spent their entire careers characterizing exterior ballistics.

 

[pdog06]

Thanks for the info. I was kinda figuring it would be the extreme, but probably wouldnt do it. I have some loaded in new brass for my other 6br so I will give them a try just to see though, hopefully this weekend if the rain and wind ever stops.

The 87's work outstanding in my 8twist with 30.3g of varget. My best 5 shot 100yd group so far is a .172", and on my prarie dog trip this past august my longest kill shot was 852 yds with it.

So it looks like anything under 80gr should stabilize, and maybe some over 80 depending on bullet type.

thanks again for the info guys. I'll post back if mine stabilizes these or not.

 

[TRECustom]

pdog, I'll watch this thread. I have a 12 twist McGowen that I'm stocking now and will start to shoot for groups in a couple of weeks.

Tom

 

[crashnrondo]

I shot 87gr v-max's in my 24" 1-12 Douglas, I never got them as accurate as the 80gr Bergers but they did just fine.

 

[pdog06]

I shot 87gr v-max's in my 24" 1-12 Douglas, I never got them as accurate as the 80gr Bergers but they did just fine.

Good to know. It'll be a bit before I get to check them out. I was at the range today and brought it along, but my loads with new FL sized and trimmed lapua brass will not chamber in the barrel. After re-measuring things when I got home the only thing I can find is it has a very tight headspace, so I will have to crank my dies down some more and reload a few to try out, or just reset the headspace.

 

[Steve Blair]

Do you have a set of headspace gauges for 6BR? If not, you should order a set from PT&G. They sell them reasonably and any Savage owner that changes barrels should have a set for each chambering.

I have never been comfortable with the cartridge case (fired or otherwise) method of setting headspace. Brass cases are made to be malleable, hardened and ground steel gauges are not.

FWIW, I have a set of gauges for every chambering I own and some that I no longer have, like .50 Browning.

 

[pdog06]

I do not have a set myself for it, but have access to a set to borrow. Did you wanna sell me some ;D

I have a set for almost every other chamber I have. I do want to buy a set for .308, but also have access to a set of them if needed first.