New 6 BR Project

[Golfer]

I am having my first 6 BR rifle built and have some questions regarding chambering.
I will be using 75 grain V-Maxes as my heaviest bullets for woodchucks but may want to use 58 or 65 grainers for prairie dogs. I think a 1-12 twist will work best. I will want a no-turn neck (.271-.272) I will be using Lapua brass.
When I make up a dummy round to send to my gunsmith, how should I set it up? I think that I should seat a 75 V-Max deeper than one cailber in the neck. This would allow me to use the shorter lighter bullets and still be able to reach the lands if needed. This would also allow for some throat erosion over time that would require seating out further. I am not sure how much freebore to specify.
Any other tips or suggestions?

 

[RonAKA]

Take this from somebody who has not ordered a custom barrel. I looked at it, but now have a 1 in 12 twist LRPV Savage in 6BR on order. So I now view it from the other way around. What can I shoot in that barrel...

Some suggestions which I will admit are a bit cynical. Your gunsmith is not likely to get a chamber reamer cut just for you. He is going to use what he has, or rent one. You may want to consider having your own reamer made for $138 by Pacific Tool and Guage. I would try to get through to Dave Kiff to discuss. See this article:

http://www.6mmbr.com/Kiffreamer.html

I think I would have more faith in them making a good reamer with the correct throat length dimensions based on discussion rather than sending a dummy cartridge to a gunsmith.

On your bullet sizes if varmints are the only objective, I'm not sure you need the 75 grain option. You may want to consider just the smaller ones and go with a 1 in 14 twist to match. Little more velocity, accuracy, and less compromise on throat length.

Just thinking out loud...

 

[Kenny474]

If you plan on shooting the 75gr V-Max as your main bullet, and still want to be able to shoot the light stuff and touch the lands than you may have to make a slight compromise and go with a little shorter throat than if you were to shoot only the 75's. The 12 twist should work great for both weights, and the slight increase in bullet RPM's over a 1-14 will add to the splat effect on varmints as well. As well as the 75's will come in handy with their extra BC when you are presented with long shots or the wind kicks up.

You should definitely have Dave Kiff grind you your own reamer as well. That way your chamber is set up to your brass and bullet combo, and you don't end up with whatever the smith has kicking around. Dave will also most likely be able to help you figure out what you will need for a throat so you can get good performance from both 75gr and 65 or 58gr bullets. I don't think there is enough difference in the length between those bullets that it will cause too much of an issue, though I am not completely sure. You will probably still need to send him some dummy rounds, but I think the end result will be worth it.

Something to think about: I run a 9 twist .222 and my buddy runs a 12 twist .223 and we shoot a lot of squirrels together, and whatever else we can find for pests. Even though he has more velocity with 50gr V-Max's,(3200 vs 3400) my .222 has a lot more splat effect. I can only attribute it to the higher bullet RPM's from my 1-9 barrel. So even if you lose a little velocity to the 1-12 twist, it should make up for it with damage on target. I am not sure how much difference will be between 1-12 and 1-14, but I doubt it will hurt.

Good luck with the project. I hope it turns out well for you.

 

[oldroper]

I am having my first 6 BR rifle built and have some questions regarding chambering.
I will be using 75 grain V-Maxes as my heaviest bullets for woodchucks but may want to use 58 or 65 grainers for prairie dogs. I think a 1-12 twist will work best. I will want a no-turn neck (.271-.272) I will be using Lapua brass.
When I make up a dummy round to send to my gunsmith, how should I set it up? I think that I should seat a 75 V-Max deeper than one cailber in the neck. This would allow me to use the shorter lighter bullets and still be able to reach the lands if needed. This would also allow for some throat erosion over time that would require seating out further. I am not sure how much freebore to specify.
Any other tips or suggestions?

My 6Br has a 1/14 twist barrel been happy with the 62/70gr bullets you might want to look at 1/13 or 1/13.5 twist barrels. I agree with seating the V-Max deeper but remember your going to give up some case capacity vs shooting the 58gr bullets and measure all three bullets to ogive length might find them pretty close. Most gunsmith have what called throating reamers and if he has a 6br reamer he should be able to throat without having to order a reamer there may be a compromise between the three and that something you need to talk to him about once you make up those rds.
Sound like a good varmit rifle.

 

[NorCalMikie]

If you go with a 1-8 twist you can shoot anything.
Build yourself the "dummy round" with the bullets seated where "you want them". It's your barrel so get it chambered the way "you" want it.
If it's going to be a "critter getter" you will be burning a lot of ammo and the throat will only get longer. You don't want to look back and think "I wish it had a shorter throat".
With the V Max and VLD bullets being long and pointy you'll want to jam them into the lands.
I prefer as much bullet contact in the neck as I can get. (remember the throat will only get longer)
Set the lightest bullets at the shoulder neck junction and have the chamber throated to that.

 

[fdshuster]

Golfer: As NorCalMikie said, get your own reamer. A few years ago I was anxious to get my hands on a 6BR .272" no-turn neck reamer, and into the hands of my gunsmith, so I took an off-the-shelf with a .104" freebore. It worked fine at that time for the intended bullet, the 95 gr. Berger VLD, easily touched the lands with plenty of case neck contact. At 1600 rounds fired now, (and still no trace of firecracking in the throat, a lot of barrel life left), the 95 gr. Berger is just barely clinging to the front edge of the case mouth when touching the lands. Had to go to the 107 gr. Sierra. The reamer was sent back to Pacific and re-ground with zero freebore, a new Krieger blank chambered with it, and I'm able to seat all bullets to touch the case neck filled with the .243" bullet diameter. I'm even able to seat the 107 Sierra to touch if I'm willing to give up a little powder space, but that bullet is kept for the long throat 6BR anyway. Starting out with a deep throat is giving up a lot of choices of light & medium weight bullets, and has the same effect as firing many, many rounds with the resulting erosion. As Mike said, when I measured and saw the erosion developing, I began to think, " I wish it had a shorter throat".

 

[NorCalMikie]

Frank: Unless he planned on chambering "lots" of barrels, I think it would be better to have the barrel chambered to a dummy round rather than spend the extra $$ on a reamer that he might only use once??
But than again he could chamber the new barrel and sell the reamer to someone else. $$ is $$.
And most of the barrel makers could cut the throat to just about and freebore he could want.
Just make sure you don't get a "off the shelf" reamer cut. (been there, done that )

 

[MarkS]

Golfer,

Your plan sounds great. I like the 12 tw for my GH guns. I like the 70 Gr Sierria Blitzknig. I think the accuracy is better than most tipped bullets. This bullet needs a very short lead. You want to seat the Vmax down like you are talking about.

Mark Schronce

 

[Ackman]

Considering the cost of a custom rebarrel, it's a good idea to just buy your own reamer and have exactly the chamber you want. My 6BR has a 14 twist barrel, chamber is 0 freebore. The 6BR case has a very long neck. I'd rather have bullets seat well down the neck and a chamber that's minimally longer than caselength. In my gun a 75Vmax is the most I'd ever want to use.....just touching the lands it will seat to slightly below the neck/shoulder junction. A 65VMax is .075" above the neck/shoulder junction. And 55/58's are a ways up from that. Remember the throat will change with rounds fired. When you see how fast and flat and accurate those lighter bullets shoot - especially the 55BT - you'll probably want to use them too. That 6mm/55 will shoot quite a bit faster than a 22-250 can push 55's.

 

[surveyor86]

I talked to Dave last week about freebore length on my 6Br Norma build. I too was not sure what to go with. I'm truing up a Remington 700 action and putting a krieger LV 1:8 on it. I'm going with the .272 no-turn neck and lapua brass. I have the intention of shooting 75s on up to 90-95 grain bullets. I'm not ruling out the 105-107 bullets at some point but for now thats the plan. With that said Dave recommended a 0.077" free-bore for my build. Based on all that info he said as throat erosion occurs the free-bore would get longer(no big secret) and at that length, the throat would wear into the sweet spot for the heavier bullets and and i would wear out the barrel before i had any problems getting the lighter bullets to jam. To insure you get EXACTLY what you want I would get Dave on the phone and let him grind the tooling for your rifle. He is very nice to talk with and a wealth of info. I can't wait to get mine going. I should have my reamer in about a week. My old man and I do our own smithing so the money spent is worth it to us, but everybody is different. My 2 cents