Nk turning the 6BRA

Discussion in '6BR, 6BR Improved & Wildcats' started by tn noshooter, Dec 17, 2017.

  1. tn noshooter

    tn noshooter Silver $$ Contributor

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    In the process of having a new light gun chambered in the 6BRA 268NK and wanting to go ahead and have the necks turned when it gets here. Using Laupa brass what would you think I need to turn to for the first firing. I know 2,to 3 clearance is normal so is 11.5 to much to start leaving you with 266. Or would you go with 12 leaving you with 267. This is for 600 yard BR and Alex Wheeler is doing all the work
     
  2. Phil

    Phil Gold $$ Contributor

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    Seat a bullet that you are intending to shoot and measure the neck, then figure out how much clearance you want to have, Alex should be able to help you with your decision.

    Phil.
     
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  3. dmoran

    dmoran Gold $$ Contributor

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    I favor thin necks, for gains in neck tension consistency and less demand of annealing. Plus I like clearance and favor +003". For those reasons, myself would take more off then less.
    Donovan
     
  4. gunsandgunsmithing

    gunsandgunsmithing The best tuners and wind flags on the market Gold $$ Contributor

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    This is the best method. Antime you're measuring anything that's potentially as critical as neck brass thickness, you should eliminate any stacking of tolerances and avoid as much as possible, measuring in tenths. There are simply many more variables to consistently measuring anything that small consistently. I spent years in true tool and die making. Very few people outside of the very best shops have a good understanding of what's really involved in working with those dimensions and a thin piece of soft, small diameter brass is not the best place for even very experienced die makers to claim perfection in measuring. There are some tools that help, but they must be properly calibrated and used...in a 68-72 degree environment.

    The only dimension that matters is what the finished loaded round measures. This is much easier to get a consistent measurement from too. Bottom line, anytime someone quotes measurements to 4 decimal points, I take them with a grain of salt until proven to be accurate.

    That said, I prefer to use no less than .002" clearance on a 6mm anything.---Mike Ezell
     
    Last edited: Dec 17, 2017
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  5. AlloyTargets

    AlloyTargets Site $$ Sponsor

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  6. newbieshooter

    newbieshooter :) Silver $$ Contributor

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    for .268 neck - accounting for .2435 pressure ring - I trim to .0112. Seated bullet measures just under .266
     
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  7. gunsandgunsmithing

    gunsandgunsmithing The best tuners and wind flags on the market Gold $$ Contributor

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    That's very good! When was your tooling last sent in for calibration?
     
  8. GSPV

    GSPV A failure to plan is a plan for failure. Gold $$ Contributor

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    Man, there is no way that I'd go to the line with 1 thou clearance.
     
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  9. Curious

    Curious

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    I would have thought asking the man who is building your rifle and who has possibly the most experience of this case at the minute might make the most sense - dont you?

    Instead you now get differing opinions from guys who you most likely dont know or can't tell how credible their opinions are based on what level of experience or success?

    Realistically in a LR benchrest rig you are not going to win or lose a comp based on your neck clearance so long as its within a sensible tolerance. At least 0.002" would be accepted and maybe as much as 0.004", you could play it safe and go for 0.003" which would mean cutting them in the region of 0.011"

    So, you aim for a loaded round of 0.265" and once you have turned a sample it might come in at say 0.2645" or maybe 0.2655" or maybe even your target 0.2650" - once you have a size that is close within half a though you could run with it, making sure they are all the same is far more important than worrying over half a thou or hitting the pre-set number dead nuts.

    There are literally dozens of things more significant to shooting small LR groups than exactly how thick your neck is so long as you have a workable clearance and they are all the same. We could debate all day over whether 2 thou is better than 3 thou but to test this in a way where we could draw really meaningful conclusions is extremely difficult and most likely not worth the hassle.
     
  10. P1ZombieKiller

    P1ZombieKiller Gold $$ Contributor

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    Consistency is the key.
     
  11. GSPV

    GSPV A failure to plan is a plan for failure. Gold $$ Contributor

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    The point that I was trying to make is that a .266 diameter loaded neck measurement gives you *1* thousandth clearance per side in a .268 neck. *Not* 0.002.
     
  12. tom

    tom Gold $$ Contributor

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    .0107" and buy some vapor trails and be done! I found no reason to ever return BRA cases down the road. The opposite is true with dasher cases, yes even hydro formed, all though those showed the least thickening. BRA cases aren't thickening at all with enough firings to be retired from match use, at least that is my experience on my brass anyways.

    Tom
     
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  13. jackson1

    jackson1

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    tn noshooter, Last month I received my Alex Wheeler Built rifle (6 BRA). Have not shot it yet, but in my conversations with Alex and his many national winners, I am confident the rifle will shoot better than me. Alex is on the cutting edge of the sport and will guide in making the correct neck turning wall thickness decision.

    gunsandgunsmithing, I could not agree more with you on precision measuring to the tenth. Another retired journeyman tool and die maker, here. Way to many influencing factors, other than different hands.
     
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  14. foxguy

    foxguy Silver $$ Contributor

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    Good evening Tom,

    Just a Question. Are you shooting the 6MM BRA with a .268 neck.
    and then trimming necks to that .0107 based on the Vapor trail loaded round.

    What is the of the diameter of the Loaded Vapor Trail round? .xxxx

    Thanks,
    Steve.

    I'm new to turning necks- still learning.
     
  15. tom

    tom Gold $$ Contributor

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    Yes, yes, and it pits me right +-.0001" of a .2650 loaded round. I've always had the best luck on my 6mm's with .0025" or greater clearance. When I set up I try to get close to .0030". I haven't noticed any negative effects if I end up a little more, bit have experienced strange shots if I get to snug.

    Tom
     
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  16. tn noshooter

    tn noshooter Silver $$ Contributor

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    Thanks Tom for the comments , I wasn't trying to get a exact number but more of do I need to turn to say 267 loaded to fire form then return after that for a final. But Alex did call and get me pointed in the right direction. I did try him to start but he is one busy guy and I know he doesn't have time to reply to every little thing .

    Thanks Richard
     
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  17. dedeadeye

    dedeadeye

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    Richard, I have been turning the necks on my BRA to .0105. That is in Alex's .268 reamer. Those cases were used to set a new 1000 yard world record last spring. I find that there is no downside to the extra clearance.
    Roger Gower
     
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  18. Joe R

    Joe R Silver $$ Contributor

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    Amen brother. Safety first.

    IMO any round with less than .003 neck clearance is a potential problem (over pressure). Hot gasses or brass in your face will ruin your day. If you get any of it in your eye, it may be game over. Given that I know of only one benefit of tight necks and given the potential risks being so severe, it defies reason why would anyone want to have less that .003 neck clearance.

    I totally agree with:

    I go one step further, I prefer .005 clearance for my F-Class rifles, just in case. This may not apply to to the 6 BRAckley, but necks do thicken up as brass is fired and brass flows forward. So periodic checks are necessary. And you could always pick up a speck of dirt while on the firing line.

    I firmly believe in neck turning to get even neck tension all around the bullet, there is no other way. Some people use thin necks to control neck tension, others use annealing. IMO annealing is a superior way to relieve stress in the brass and extend brass life. It can also help control neck tension. Given all the benefits of annealing, and how easy it is, it seems silly not to do it.

    Regards,

    Joe
     
    Last edited: Dec 26, 2017
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  19. Joe R

    Joe R Silver $$ Contributor

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    IMO the best neck turner on the market is the Hornady, at around $100 there is nothing else that even comes close to it.

     
  20. kvd

    kvd Silver $$ Contributor

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    There is a lot to this statement that warrants closer examination. We tend to turn necks so that cartridges that wouldn't otherwise fit will work in tight custom chamber necks and think in terms of safe and proper clearance. However the chief benefit of neck tuning may in fact be more consistent neck grip and bullet release. I'm not smart enough to begin to understand what is going on within the cartridge at the neck-bullet-chamber interface during those first critical microseconds after primer ignition but there seems to be a relationship between the grip of the cartridge neck on the bullet, the amount of room the cartridge neck can expand before it contacts the chamber neck wall, and the distance the bullet is from the lands. As it stands now, trial and error is the only way to arrive at a satisfactory combination of these three important variables.

    I turn my necks down to 0.0102 inch for Alex's 0.268 neck and and have had best luck so far with seating Berger 105 grain Hybrids at 0.005 off the lands. After break in, still dealing with a relatively fast barrel. The last outing in approximately 50°F weather, MV averaged 2967 ft/sec measured with a Labradar using 29.7 grains of H4895.
     
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