6BR build: question chamber dimension

[knguyen]

background:
Bat MB action:
barrel 1:8 twist Krieger.
Question for more seasoned shooters?
when getting ready to have my gunsmith finish my barrel: question is do I have him finish with a tight chamber ( which require neck turning Lapua brass to fit round) or get a loose chamber(no neck turning required chamber)?

what are the advantages of one over the other?
what are disadvantages?

accuracy?
brass life?
I have all gear needed to neck turn to dimensions required.

thanks alot,
Khanh

 

[LRPV]

In my opinion the only disadvantage to a tight neck is the time it takes to turn the brass.

 

[knguyen]

other then the labor to turn the neck, what then would you say are the postive benefits of having a tight chamber?
khanh

 

[LRPV]

I spend a lot of time and money trying to make every round the same as the last and neck thickness is not consistent without turning. Plenty of guys have done and will continue to do fine with no turns ( I shoot dashers with each type) but I just believe it's one more variable that can be eliminated. Not sure what discipline you're going after but the groups aren't getting any bigger and I need all the help I can get.

 

[knguyen]

i am building my first 6BR, shooting is benchrest,
goal is to be competitive at 600 yards.
currently shooting at 200, 300 yard
goal to shoot competitively with consistent smaller and smaller groups.
learning each time I go shoot.
trying to eliminate as much variables which will help me become more consistent with groups
Goal is the smallest groups i am capable to shoot with my first custom rifle.

 

[LRPV]

I can't quantify how much it helps but when done right, I'm pretty sure it doesn't hurt a thing. If not done right, I do think it can hurt.

 

[knguyen]

in your experience what components of your shooting does neck turning help you?
group sizing?
vertical efffects?
i am on the fence about getting a no neck turn chamber versus neck turn chamber.
i know that a simple skim of the neck to just make sure neck thickness symmetrical can be beneficial
i am currently shooting a savage model 12 6BR in which I shoot standard lapua brass no neck turning done and still shoots quite well
but iam now moving up to my first custom rifle with bat action and nicer stock and better barrel so i am trying to squeeze out as much precision/accuracy as i can.

 

[LRPV]

I'm not experienced enough to say for sure yet. Hopefully someone who is will chime in.

Consistent neck tension, consistent release, should allow for tighter ES, vertical and groups.

 

[knguyen]

thanks for your input, i am now at the learning stage where i am trying to remove as many variables which will make my shooting of smaller and smaller groups possible
Iam getting lots of trigger time in and learning each day,
thanks
khanh

 

[Erik Cortina]

Consistent neck tension as well as concentricity are the reasons I neck turn.

If you don't do everything possible to make your rifle shoot well, the first time you almost win, or almost shoot a record, you will wonder if it would have happened with turned necks and you will kick yourself for not taking the time to turn necks. BTW, that feeling applies to more things than neck turning.

 

[jrm850]

You can always open the tight neck if you find you don't like it.

One question to ask is if you want to be dependent on brass uniformity from the manufacturer or control that variable yourself?

 

[dkhunt14]

I believe if you don't go with a tight neck and a complete turn, your bullet is not concentric or centered in the case. You will also not have consistent neck tension. If you go with a no turn and skim you have to much clearance between the chamber and brass and you overwork the brass. Competitions are won by a few thousandths at 600 and 1000 yards on a lot of days. Matt

 

[CatShooter]

If you get a no turn chamber and and skim the necks, your life gets easier, with no down side.

I have owned a lot of tight necks, and never again.

If you are shooting 600 yds, then you will be shooting long bullets, which means they will most likely be seated so the base is at or below the neck/shoulder junction... and if you have a tight neck chamber, you WILL have, and must manage, the dreaded "Donut"... it is a real pain in the azz.

Get a no turn chamber, and you have no donuts.

If you get a properly made no turn chamber and skim your cases, you will NOT have concentricity problems, or any of the other problems that have been mentioned above.

 

[LRPV]

If you spec a reamer with the correct freebore for the bullet you plan to shoot, you will not have to worry about a donut.

 

[Phil]

Measurea box of Lapua brass......There are inconsistancies.....Not much, but they exist.

Turning necks eliminates these, consistancy is key to small groups, why not eliminate as many variables as you can.....

IF you get a nice neck turning lathe and a good neck turning tool you too will see that it`s no big deal....

You also need to spec your own reamer, in my opinion.

Take a piece of your neck turned brass and seat a bullet, that you intend to shoot, into it and send it to a reamer manufacturer so you get exactly what you want / need for your rifle.

Phil.

 

[comagutsa]

i run a .272 no neck turn in my 6BR with .105 freebore for my berger 105gr vlds, loaded lapua round is .269
after talking and reading up on pros and cons , some say turn, some say don't neck turn...
in the end i went with no neck turn because it was a pain in my last gun i did it for (lazy haha), but i know a few blokes with 6BR's and they tried turn and no turn and they didn't see any difference in groups , even read a few articles of bloke who won big comps and they didn't neck turn so lazy me went with no turn haha

the blokes i shot with not doing turn are still getting 1-2" groups at 500m

i'm might skim them one day but no time soon

 

[knguyen]

so the question is:
a: no neck turn chamber: which is just do light skim of brass to get it more concentric

or

b: tight neck chamber: which will require more neck turning to make sure my rounds load properly

for the tightest groups possible, what would seasoned shooters choose: A or B
i know there is no solid answers but want advice
thanks
khanh

 

[22turborimfire]

I'm running a no turn but I still turn to a specific loaded round OD. I went this route with the Dasher because of the short neck area .All the other 6brs are running a tight neck for now but that's subject to change as well.

 

[wnroscoe]

If your spending the money for a full blown custom I say turn the necks. Turning necks to a 100% clean up yields consistent neck tension and velocities that help produce very flat vertical and small groups.

My 6BR Reamer has a .269" neck with .104" Free bore and was designed around the older paper box 6BR brass. My old brass was turned to .268" loaded. While there's no magic reamer, this ones pretty close. I just loaded several rounds from the blue box, not paper and the loaded necks are running .2675" on average, this is with un-turned brass.

I imagine that if I turned these necks they'd measure .266" giving .0015" per side clearance. For a tight neck BR of today using the blue box stuff I'd probably run a .265" to .267" neck depending on my brass. At the end of the day, the brass is going to dictate what you end up doing for the neck dimension's and your bullet selection / COAL is going to dictate free bore.

I've built numerous no turn neck LR Tactical rifles and numerous BR rifles with both no turn and tight neck chambers in 6mm. I've found that if quality Lapua brass is used and a high level of care is used when loading and tuning ammo .250" moa groups are no problem. If you're looking to get into the .1's or .0's I'd plan on turning necks.

Don't over complicate it, enjoy your build and make small holes.

 

[dkhunt14]

If you get a no turn chamber and and skim the necks, your life gets easier, with no down side.

I have owned a lot of tight necks, and never again.

If you are shooting 600 yds, then you will be shooting long bullets, which means they will most likely be seated so the base is at or below the neck/shoulder junction... and if you have a tight neck chamber, you WILL have, and must manage, the dreaded "Donut"... it is a real pain in the azz.

Get a no turn chamber, and you have no donuts.

If you get a properly made no turn chamber and skim your cases, you will NOT have concentricity problems, or any of the other problems that have been mentioned above.

If you skim the necks in a no turn the bullet is still off center. Maybe only a half thousandths but still off center. That is not concentric. If you use a bushing die and size the brass the neck pushes in farther in the thick side and is out of round. The PPC guys shoot the smallest groups of anybody and they all use tight necks. If it shows at 100 yards I guarantee it shows more at 600. You need to turn with 3 to 4 thousandths clearance and the neck in the gun has to be small enough to allow that. If you throat the gun out to make the pressure ring in front of the neck shoulder junction the donut doesn't matter. It also helps relieve pressure because the capacity is bigger. If you turn them right and manage your brass right you don't get a donut. I always run an expander mandrel in and if there was a donut it is now on the outside where it doesn't matter. And any amount of skimming in a no turn chamber lets the brass have too much clearance and when fired moves a lot to get to chamber dimensions. Then when you size you move them back a lot to get the bullet grip. Now you are overworking your brass and harden them a lot quicker. I have never had a problem with donuts by shooting a tight chambered gun and turning my brass to give proper clearance. Most brass is always a thousandths or more difference from thick side to thin. Matt