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(How) is neck friction (cartridge/bullet) an issue to | ||
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The issue on safety is only if you don't have enough "grip". The bullets in the magazine can be driven back into the case on recoil thereby changing the entire characteristics of the load. Pressures can increase excessively creating a dangerous situation, particularly if loads are near maximum. Not too much safety concern on excessive grip except necks can split if the cartridge remains loaded for an extended period. If it were possible to almost seal the bullet into the case your pressure curve will be altered considerably creating a peak pressure greatly in excess of SAAMI maximums in the cartridge which might lead to possible rupture of the case. As to accuracy, there is considerable effect. I've done the most testing in 338's. The ideal grip for the bullet in several Win Mags seems to be about .002" with recenly annealed brass. Bullets in the magazine are able to withstand the recoil without being driven back and accuracy is not adversely affected. In my experience there is a bit more accuracy with a .001" grip but this light friction enables bullets to be driven into the case. For single loading a light grip seems to produce better accuracy, probably because of consistency in the friction in the neck. Accuracy deteriorated for me at .003" grip and above. Any more than that seemed to make little difference as there was not enough elasticity in the brass to matter much. These values would probably change in smaller calibers in the varmint class. Because of reduced recoil I generally settle on light grip in varmint class rifles. I've not done much testing on smaller calibers so can't be too specific there. However, in single loading the lighter grips seem to give the best accuracy across the board on all calibers. | |||
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Neck friction is a major factor if you use new virgin brass. That nice clean case with a nice smooth bullet produce very little friction. That is why "all" factory ammo is crimped. With fired cases, you have a "harder" case with carbon on the inside and the neck tension is greatly increased, and crimping is seldom needed. | |||
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Bench rest rifle, and rifles set up for pure accuracy have 0 tolerance chambers which equates to a thousands expansion before being stopped by the neck-chamber walls... A normal hunting rifle will have 200 to 300 thousands expansion allowed and that's fine... On big bores with recoil I always turn three or four thousands off the resizer button to facilitate holding the round tightly so as to prevent bullet set back and it also takes the place of a crimp when used with a powder that fills the case....this theoretically has some bad effect on accuracy but in a big bore you won't be able to find it.... ------------------ | |||
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I'm sure Ray is a bit off on the expansion allowed in any factory chamber. 200 to 300 thousandths is a quarter inch. That won't work. .002" to .005" is tolerable. Any more than that will result in split necks, or worse. | |||
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