Partial Neck Sizing


October 6, 2011, 02:49 PM
Does partial neck sizing in anyway affect load pressures? I always neck size and just recently purchased a Bushing die and was wondering if I'm going to be able to safely shoot an old receipe with partially sized necks.

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October 6, 2011, 03:42 PM
No worries. Do size enough of the neck to hold the bullet well.

October 6, 2011, 03:48 PM
I had done like Walkalong, stated and my accuracy was ok but then I necked to top of shoulder and put a light crimp on the projectile 7mm mag and my my accuracy did improve moreso... these are my results.

October 6, 2011, 03:54 PM
The idea of partial neck sizing is to leave part of the neck unsized to help line the round up in the chamber and help it get started more in line with the bore. True or not, that is the idea. You only need to leave a very small part unsized to do this. Size plenty of the neck, at least one full bullet diameter, or more.

October 6, 2011, 05:02 PM
There is little doubt that getting the bullet centered better in the bore improves accuracy.

The issue is that there are still many other things that can reduce accuracy cancelling any gains from the better centering.

If the case neck thickness is not uniform and the chamber very accurately aligned with the bore axis, the bullet is still not centered in the bore.

October 6, 2011, 05:37 PM
All true. :)

October 6, 2011, 06:58 PM
Thanks guys. I thought as much but, just wanted some reinforcement. I partially neck sized about 2/3 of the neck. Should be enough??

October 6, 2011, 08:38 PM
Probably, but what caliber? Some of them have really short necks.

October 7, 2011, 11:18 AM

October 7, 2011, 12:49 PM

Cartridge cases are seldom perfect, one big problem reloaders face is if the cartridge case has unequal case wall thicknesses. If one side of the case wall is thinner it will expand more on that side and have a bulge on that side of the case. this bulge can push the case off center with the axis of the bore.

Bottom line, the majority of resized and reloaded cartridge cases have better accuracy when partially resized and the shoulder of the case only bumped back .001 to .002.

There is a reason why competitive shooters use Lapua brass and its called quality control. On some cartridge cases where the case walls very widely in thickness the act of resizing the case can cause the case to warp and become banana shaped with the base of the case no longer 90 degrees with the axis of the bore.

The chamber pressure on a neck sized or full length resized case is insignificant, "BUT" the length of time the base of the case is exerting pressure on the bolt face is longer on a neck sized only cases. Also you should keep your bolt lugs lubed with neck sized cases to prevent wear on the lug and lug recesses in the receiver.

October 7, 2011, 08:16 PM
"I partially neck sized about 2/3 of the neck. Should be enough??"

There is never any advantage to sizing necks below the base of the loaded bullets.

October 9, 2011, 11:33 AM
2/3 of the neck is fine, especially if the cartridge has an inherently long neck. Are you using NSO dies or FL dies?

October 10, 2011, 12:32 AM
Thanks. NSO.

October 10, 2011, 01:50 AM
I partial neck size when I'm using new brass or once fired brass not from my chamber. I think it honestly helps to minimize accuracy problems during the first fire forming session. I don't do this once my brass has been formed though, no real need.

October 10, 2011, 08:43 PM
I do this when it's appropriate as it makes the brass last a lot longer. I put a thick washer (1/8th inch or so) that has a hole that fits allows the FL die to poke through. This way so far has proven good with a variety of calibers I shoot/reload for. This way I find that I don't even need to adjust the die when I FL resize which is what will be need after a couple or so neck resizes. About every third time it's fired will require a F/L resize. This works well most of the time for good ammo. I occaisionally need to readjust the die if I am being finicky about a shoulder set back for some of my extra special show off target rounds:cool:

October 10, 2011, 10:56 PM
In 243 win. size about 1/2 of the neck. Testing showed sizing more than 1/2 degraded accuracy. The unsized half will take about 3 firing to form to a factory chamber. Rem 40x neck turned or Rem 600 non-turned no expander used for me. Control shoulder bump also. (

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