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Rifles, Reloading, Optics, Equipment
Reloading
Neck Tension (lee collet)
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<blockquote data-quote="boomtube" data-source="post: 543865" data-attributes="member: 9215"><p>What gets called "neck tension" is not <u>tension</u> at all, it's usually just a difference in the diameter of a bullet and the neck hole. The lowest bullet grip we can obtain that still holds the cartridge securely is best for runout and accuracy. Controlling ignition start pressure is best done by adjusting bullet jump to the lands (aka, OAL) not agonizing over 'neck tension'. How tightly the bullet grip actually is depends more on the hardness of the brass than the differences in neck diameter. </p><p> </p><p>A smallish neck hole IS more difficult to seat bullets into but if you mic the neck of a loaded round and then mike it again after pulling the bullet you will see that the neck only shrinks back about 1 thou, the rest of the original difference simply got permantely stretched and only the last thou actually holds the bullets in place. Fact is, a high "tension" effort forces most bullets to cock on intial seating and contributes to bullet runout; runout is NOT good for accuracy. Years ago, after using my first collet neck die I got more and retired all of my conventional neck dies.</p><p> </p><p>Lee's collet die mandral is sized to produce a thou or so smaller neck on MOST cases but that can easily become different as we size and fire the cases repeatedly; hard brass springs back more after sizing. Some people (wrongly in my opinion) seek smaller necks by sanding down the mandral but annealing case necks is a much better method of controlling the finished neck diameter than grinding on the mandral.</p><p> </p><p>There is no point in putting a lot of ram pressure on a case in Lee's collet die. The brass is soft and swages down easily. Necks cannot be made smaller than the mandrel allows and it does't take a lot of pressure to reduce the fit to as small as can be done. Excessive pressure will first swage visible but harmless longitudial lines in the necks and, if the pressure is continued, the top of the die will strip and pop out. That soft aluminium top cap is made to serve as a safety feature to prevent the ham-fisted from damaging their die body or press.</p><p> </p><p>Lee's die, nor any other, can't make good necks out of bad necks, all it can do is avoid making the necks worse. And no seater from any maker or at any cost can seat straight ammo in bad necks.</p></blockquote><p></p>
[QUOTE="boomtube, post: 543865, member: 9215"] What gets called "neck tension" is not [U]tension[/U] at all, it's usually just a difference in the diameter of a bullet and the neck hole. The lowest bullet grip we can obtain that still holds the cartridge securely is best for runout and accuracy. Controlling ignition start pressure is best done by adjusting bullet jump to the lands (aka, OAL) not agonizing over 'neck tension'. How tightly the bullet grip actually is depends more on the hardness of the brass than the differences in neck diameter. A smallish neck hole IS more difficult to seat bullets into but if you mic the neck of a loaded round and then mike it again after pulling the bullet you will see that the neck only shrinks back about 1 thou, the rest of the original difference simply got permantely stretched and only the last thou actually holds the bullets in place. Fact is, a high "tension" effort forces most bullets to cock on intial seating and contributes to bullet runout; runout is NOT good for accuracy. Years ago, after using my first collet neck die I got more and retired all of my conventional neck dies. Lee's collet die mandral is sized to produce a thou or so smaller neck on MOST cases but that can easily become different as we size and fire the cases repeatedly; hard brass springs back more after sizing. Some people (wrongly in my opinion) seek smaller necks by sanding down the mandral but annealing case necks is a much better method of controlling the finished neck diameter than grinding on the mandral. There is no point in putting a lot of ram pressure on a case in Lee's collet die. The brass is soft and swages down easily. Necks cannot be made smaller than the mandrel allows and it does't take a lot of pressure to reduce the fit to as small as can be done. Excessive pressure will first swage visible but harmless longitudial lines in the necks and, if the pressure is continued, the top of the die will strip and pop out. That soft aluminium top cap is made to serve as a safety feature to prevent the ham-fisted from damaging their die body or press. Lee's die, nor any other, can't make good necks out of bad necks, all it can do is avoid making the necks worse. And no seater from any maker or at any cost can seat straight ammo in bad necks. [/QUOTE]
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Neck Tension (lee collet)
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