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Thread: neck tension

  1. #1

    neck tension

    Hi all, does the neck tension raise pressures, I use rcbs dies, is there a standard neck tension or does this vary with the brass you use.

  2. #2
    If you have brass with thicker or thinner necks the neck tension will vary. I would also assume that the elasticity of the brass will also affect neck tension

  3. #3
    The standard neck tension we use on hunting loads is 0.002 inch. IE the outside neck diameter is 2 thou smaller on a sized case than the outside diameter of a loaded round. We have found that this works well for hunting and field rifles. Target or bench guns may benefit from slightly less neck tension. however they may be prone to the bullets moving out of the case due to recoil or pushing into the case during feeding from the magazine if one is used. There is never a free lunch with altering neck tension on a given load. nothing affects accuracy more quickly . The grip of the case neck provides resistance to the bullets initial movement on combustion of the powder. Testing has shown drops in velocity and powder being not burning completely in the bore from the same load that had 1. higher neck tension and 2. was given a light taper crimp.
    Bushing dies are the best way to alter neck tension as sizing buttons are available in 0.001 increments. however on a standard die set you may increase the neck tension by polishing/ using emery cloth the expander ball on the sizing die. I would advocate caution when attempting this as one cannot obviously put material back once it has been removed. If you neck turn cases on a standard chamber dimension using standard dies then one should re adjust the neck tension of the case. The reason is:
    when you have removed materiel from the case neck, the cartridge still obturates to fit the chamber on firing. the neck now being thinner this means that compared to the dimension of an unturned case the case neck ID. is now larger due to the walls of the neck being thinner and moving out to fit the chamber. reducing the diameter of the expander ball on standard dies will give you back a more secure grip on the bullet than if the die is left unaltered. I would always advocate making a note of loaded round case neck diameters and sized case neck diameters as a matter of course,. If in the instance that you wish to alter neck tensions ,or turn cases then at least you have a reference point. I hope that is of some use to you Yours respectfully Mike Norris Brock and Norris Custom Rifles

  4. #4
    timely comments about not being able to put material back on the expander ball ! ive just bought a second hand set of dies that have been polished by the previous owner and now under sizes the neck to the extent that the cases buckle !well i am assuming this is the problem as it now measures 3 tho under size!

  5. #5
    Quote Originally Posted by brock and norris View Post
    The standard neck tension we use on hunting loads is 0.002 inch. IE the outside neck diameter is 2 thou smaller on a sized case than the outside diameter of a loaded round. We have found that this works well for hunting and field rifles. Target or bench guns may benefit from slightly less neck tension. however they may be prone to the bullets moving out of the case due to recoil or pushing into the case during feeding from the magazine if one is used. There is never a free lunch with altering neck tension on a given load. nothing affects accuracy more quickly . The grip of the case neck provides resistance to the bullets initial movement on combustion of the powder. Testing has shown drops in velocity and powder being not burning completely in the bore from the same load that had 1. higher neck tension and 2. was given a light taper crimp.
    Bushing dies are the best way to alter neck tension as sizing buttons are available in 0.001 increments. however on a standard die set you may increase the neck tension by polishing/ using emery cloth the expander ball on the sizing die. I would advocate caution when attempting this as one cannot obviously put material back once it has been removed. If you neck turn cases on a standard chamber dimension using standard dies then one should re adjust the neck tension of the case. The reason is:
    when you have removed materiel from the case neck, the cartridge still obturates to fit the chamber on firing. the neck now being thinner this means that compared to the dimension of an unturned case the case neck ID. is now larger due to the walls of the neck being thinner and moving out to fit the chamber. reducing the diameter of the expander ball on standard dies will give you back a more secure grip on the bullet than if the die is left unaltered. I would always advocate making a note of loaded round case neck diameters and sized case neck diameters as a matter of course,. If in the instance that you wish to alter neck tensions ,or turn cases then at least you have a reference point. I hope that is of some use to you Yours respectfully Mike Norris Brock and Norris Custom Rifles
    Mike,
    so a loaded case's neck increases by 2 though once the bullet is seated - is that calibre dependant?
    I'm thinking my 204 will be seated much firmer than my 308 for the same 2 thou

  6. #6
    Quote Originally Posted by brock and norris View Post
    The standard neck tension we use on hunting loads is 0.002 inch. IE the outside neck diameter is 2 thou smaller on a sized case than the outside diameter of a loaded round. We have found that this works well for hunting and field rifles. Target or bench guns may benefit from slightly less neck tension. however they may be prone to the bullets moving out of the case due to recoil or pushing into the case during feeding from the magazine if one is used. There is never a free lunch with altering neck tension on a given load. nothing affects accuracy more quickly . The grip of the case neck provides resistance to the bullets initial movement on combustion of the powder. Testing has shown drops in velocity and powder being not burning completely in the bore from the same load that had 1. higher neck tension and 2. was given a light taper crimp.
    Bushing dies are the best way to alter neck tension as sizing buttons are available in 0.001 increments. however on a standard die set you may increase the neck tension by polishing/ using emery cloth the expander ball on the sizing die. I would advocate caution when attempting this as one cannot obviously put material back once it has been removed. If you neck turn cases on a standard chamber dimension using standard dies then one should re adjust the neck tension of the case. The reason is:
    when you have removed materiel from the case neck, the cartridge still obturates to fit the chamber on firing. the neck now being thinner this means that compared to the dimension of an unturned case the case neck ID. is now larger due to the walls of the neck being thinner and moving out to fit the chamber. reducing the diameter of the expander ball on standard dies will give you back a more secure grip on the bullet than if the die is left unaltered. I would always advocate making a note of loaded round case neck diameters and sized case neck diameters as a matter of course,. If in the instance that you wish to alter neck tensions ,or turn cases then at least you have a reference point. I hope that is of some use to you Yours respectfully Mike Norris Brock and Norris Custom Rifles

    Mike
    to to what extent does work hardening of the case neck affect neck tension to the point where annealing becomes necessary?

  7. #7
    Quote Originally Posted by srvet View Post
    Mike
    to to what extent does work hardening of the case neck affect neck tension to the point where annealing becomes necessary?
    depends entirely on the brass and the loads being put through it

  8. #8
    Having piggybacked a recent post on another forum, it became apparent that one of the reasons Federal GMM (.308win) clones go south rapidly is due to the requirement of Federal brass needing to be annealing more frequently (stated @ every two firings).....

    The more you intend to use/abuse something, then the greater care in it's preparation should be taken.....

  9. #9
    How many pounds of pull weight is .002" neck tension?
    Old case? New case? Clean neck? Thick neck? Thin neck? Dirty? Copper bullet? Bronze? May-be lead?
    I'm guessing these are a factor.~Muir
    Last edited by Muir; 12-10-2014 at 19:08.

  10. #10
    Quote Originally Posted by Muir View Post
    How many pounds of pull weight is .002" neck tension?
    Old case? New case? Clean neck? Thick neck? Thin neck? Dirty? Copper bullet? Bronze? May-be lead?
    I'm guessing these are a factor.~Muir
    everything is a factor . However the 0.002 is a physical measurement of how much the neck is compressed/ sized to hold the bullet. As I said in our first reply measure a loaded round then size so that the outside diameter reads 0.002 under the measurement for the loaded round (regardless of neck thickness) . Hence 2 thou neck tension. Bullet pull weight as you correctly stated is dependent on case neck condition. if a case has a load of carbon fouling within the neck then pull weight will be higher. We always meticulously brush case necks when loading to avoid this. our technique for lead bullets uses a Lyman M die to expand/flare the case mouth and then a taper crimp to secure when seating the bullet.
    I will confess that we very rarely anneal brass as when we are sizing the brass is being moved the bare minimum . IE the shoulders and body are being set back only 0.0015 . enough to ensure smooth cycling and extraction but not enough to require annealing . There is also the question for us that due to the sheer volume that Ian and I deal with it does not become really viable. if you have the time and the inclination then by all means do so , however you will need to do this very regularly and consistently to ensure uniformity throughout your batch of brass. I trust this will be off assistance, yours respectfully Mike Norris Brock and Norris Custom Rifles

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