Neck tension ?

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  • Neck tension ?

    Can some1 please explain neck tension. I have a set of redding comp s dies on the way.

  • #2
    You need to measure the diameter of your loaded round. Take that number and subtract .003". You'll want to use that size bushing. I usually get at least two if not three bushing sizes so when you use different brass that might have a different thickness, etc., you can adjust and get the proper neck tension. You can go less, say .002" tension, but in an autoloader I would suggest a minimum of .003".

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    • #3
      neck tension is what i get everytime my wife says we need to talk
      Blackfoot is dead on

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      • #4
        So does that make crimping unnecessary?

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        • sneaky one
          Chieftain
          • Mar 2011
          • 3077

          #5
          K lab.
          If the bullet has no cannelure, crimping is not that helpful. The barnes and hornady all copper units ( with the grooves for pressure relief ) can take a slight crimp, but I rely on tension-about .004--.005. I turned the expander ball down to .259 on my Forster sizer die. All is fine. I do have a set of lee dies for the grendel- I honed and tweaked them for the wolf, F. C., & Sell-Bellot 7.62 x 39 brass to have .005- .007 tension., Those are my "plinker" brass, and or for hunts in deeper snow-I'll lose the brass. Those are downloaded a bit.

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          • RangerRick

            #6
            You want to use the largest bushing you can that will hold the bullet firmly. You should be able to chamber a round without it pushing the bullet in (measure before and after).

            Then you can check by pushing the loaded round firmly against your work bench without the bullet moving.

            The less resizing of the neck you do, the less work hardening of the brass you will get, and the longer the case will last.

            Each brand of brass will probably need a different bushing.

            RR

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            • jwilson1985

              #7
              i was told not to crimp the grendel round. just my exp.

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              • #8
                So does any 1 use a precision mic to measure the case shoulder?

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                • #9
                  The only reason you would want that is to bump the shoulder to a minimum to fit tightly in the chamber. All good and well for a precision bolt rifle, but when you need to feed reliably from an autoloader, I'm not sure you need to be messing with it. I have found very minimal if any performance advantage with it even in a benchrest rifle. Theoratically you get increased case life also.

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                  • bwaites
                    Moderator
                    • Mar 2011
                    • 4445

                    #10
                    K_Labs,

                    One of the problems with reloading for AR's is that all the subtle little things that benchrest shooters do that seem to improve accuracy from heavy bolt guns need to be set aside, and you need to go back to basics.

                    To start, you must full length size, using the largest neck bushing you can chamber in your rifle reliably. For me, that's a .292 bushing. That decreases overworking of the neck, which improves brass life. However, it MIGHT not give you enough neck tension to avoid bullet movement, depending on which brass you might be using. Since you have to full length resize for AR's (I realize that some competition shooters might not, they may neck size only, but run the risk of not feeding properly in rapid fire) all the little micrometer tricks don't have much place.

                    Once you are comfortatable loading the Grendel, then you might find that your groups are little tiny bugholes that really you don't need to do anymore twiddling with reloading schemes. If not, then consider changing one thing at a time, not more than one, JUST ONE. Shoot some rounds and see if it had any effect. It probably won't but its worth hoping for. If it doesn't, go back to square one and change something else. Do it methodically and make sure you keep track of what you change, whether its powder load, primer, brass....whatever.

                    Some people have found that a light factory crimp, which is provided by the Lee Factory crimp die, improves accuracy IN THEIR RIFLES, even on non-cannelured bullets. I haven't seen any difference, so I don't crimp. But it is worth a try once you have a good sub MOA load, and if you want to see if it might shrink the group even more.

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                    • #11
                      From Sierra.


                      Neck Tension

                      When we stop to consider the vigorous (read, downright violent) chambering cycle a loaded round endures in a Service Rifle, it becomes pretty clear it suffers abuse that would never happen in a bolt-action. This is simply the nature of the beast. It needs to be dealt with since there is no way around it.

                      There are two distinctly different forces that need to be considered: those that force the bullet deeper into the case, and those that pull it out of the case. When the round is stripped from the magazine and launched up the feed ramp, any resistance encountered by the bullet risks having it set back deeper into the case. Due to the abrupt stop the cartridge makes when the shoulder slams to a halt against the chamber, inertia dictates that the bullet will continue to move forward. This is exactly the same principle a kinetic bullet puller operates on, and it works within a chamber as well.To counteract this tendency, the semi-auto shooter is left with basically two options: applying a crimp or increasing neck tension.

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                      • #12
                        So I got my new does in the mail today. What is it exactly that controls my neck tension and what do I replace?
                        Last edited by Guest; 12-22-2011, 11:14 PM.

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                        • #13
                          I'm sure they came with instructions on how to set them up and how to set up the replaceable bushing. What I'm not sure of is if you ordered bushings with the dies. If so, then you swap out your different bushing sizes to increase or decrease neck tension. If you didn't order any bushings then there is nothing to replace until you get bushings.

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                          • #14
                            These are the ones. So is that bushing something my reloading store might sell locally or is it caliber / case specific?

                            Last edited by Guest; 12-23-2011, 02:35 PM.

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                            • Drifter
                              Chieftain
                              • Mar 2011
                              • 1662

                              #15
                              FWIW, I get the least amount of bullet runout on loaded cartridges when using the .287" bushing with Hornady brass. YMMV...
                              Drifter

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