Case separation in a .303

[TwoTone]

No, Bigbull was right and it was something I just neglected to say.
By using the full length sizing die for neck sizing, the die squeezes down the diameter of the case, near the shoulder, before the die actually toches the shoulder itself.

Perhaps it depends on the particular chamber and the die. With my .303 chamber and FL die, with the die backed out one turn, the diameter of the case is reduced beginning at a point about 3/4" up from the case rim and below.

Above that point the die does not contact the case (except for at the neck of course) and does not reduce the diameter of the case in the shoulder area. The marks where the die has contacted the case are plainly visible.

That is a fact.

I'm sure in some cases a FL die may contact the case from the shoulder on down but that isn't what happens in my situation. .303 chambers can vary quite a bit so maybe thats why we're experiencing different results here.

Regardless of all that, I still don't believe that it's necessary to purchase a Collet or neck sizing die to reduce this problem in the .303. Partial full length resizing helps a lot whether the shoulder area gets resized a little or not. The case is still nicely centered in the chamber by the un-resized portion of the neck and the location of the shoulder is unchanged and should keep the case back against the bolt face to minimize stretch.

A neck sizer is nice to have but it's not the only solution.

 

[lister]

Also, the 'one full turn back' for neck sizing isn't cast in stone. I find the amount of turn-back varies between a half-turn and a full turn, depending on chamber and caliber. MO.

 

[TwoTone]

Also, the 'one full turn back' for neck sizing isn't cast in stone. I find the amount of turn-back varies between a half-turn and a full turn, depending on chamber and caliber. MO.

Agreed, one full turn is plenty and half a turn is often enough. It's how little you want to work the brass vs. how much of the neck you want to leave unsized.