How important is consistent neck tension from cartridge to cartridge...

[ChrisBCS]

...in keeping group sizes at their smallest?

As a corollary, how necessary is annealing for the life of brass that is neck-resized only? I'm starting to notice some perceptible inconsistent neck tension when seating bullets in Rem brass that has been resized using a mandrel and collet neck sizing die after 4-5 firings.

 

[Sniper260]

Extreamly important. It creates different pressures when the powder ignites till the bullet exits the muzzle. Its not easy to get them all perfect.

 

[oldfudd]

I assume that how tightly the projectile is held by the cartridge neck impacts the internal pressure build up significantly. The pressure curve in the chamber and barrel is influenced by a number of significant variables including the speed of the powder burning, amount of free space in the loaded cartridge, projectile weight, ogive jump to lands and grooves, and friction encountered when the projectile moves down the barrel, plus others. To me the bottom line is how quickly the projectile is moving when it exits the barrel (fps). To have identical time of flight to the target (and time that it is impacted by gravity and other external variables), I believe that exit velocities must be as close as possible if you want subsequent projectiles to pass through the same hole in the target.

 

[gstaylorg]

Weighing powder accurately and neck tension may the two most important factors for consistent MV and low ES/SD. Definitely worth spending some time to get nk tension consistent. If you don't, you'll see it on the target, even at distances as close as 300 yd.