AR15 headspace

[Kryogen]

Do you size to gauge specs, or to your chamber for 223 semi (ar15, or other NR rifles).

I have been sizing gauge specs so far for my ar15 and su16F, but that requires firm contact with the shellplate, and that's a lot of bump, and probably reduces brass life quite a bit.
I did it that way so my ammo can fit any rifle.

How do you deal with FL sizing for semi auto 223 ?

 

[Ganderite]

I full length size for gas guns.

I want 100% reliability.

For bolt rifles I size the neck only, or the body just enough to get brass compression just before the bolt is all the way closed.

 

[Pr589]

I size to the lesser of the gauge or the chamber for bulk ammo. I have some semi-auto 223 chambers that are tighter than the gauge. For specific accuracy loads for the bolt action 223 I neck size and full size to the chamber.

 

[bigedp51]

I use a Hornady cartridge case headspace gauge with a less than $30.00 digital vernier caliper for checking the "fired" case length. For a bolt action shoulder bump is .001 to .002 and a semiauto .003 to .006.

Below a fired case case from my AR15, the Hornady gauge has been adjusted to read actual headspace with a headspace gauge

The case below had it shoulder bumped back .003 after full length resizing.

NOTE, If I used my .223 full length Lee die and it made hard contact with the shell holder the case shoulder would be pushed back .011. And why I use Redding competition shell holders to keep from over resizing my sized cases.

As you can see above chambers and dies can vary in size, so remember case gauges are for SAAMI chambers and military chambers are longer and fatter
Below I use the red JP Enterprise case gauge on the right for checking case diameter after sizing and as the final "plop test" of the loaded rounds. The Wilson and Dillon case gauges do not check case diameter and only check the case for SAAMI headspace length.

As you can see below the reversed .223/5.56 cases will drop further into the Wilson and Dillon case gauges and do not check case diameter. I make this point because if you buy once fired military 5.56 brass it may have been fired in a larger diameter machine gun chamber. And the JP Enterprise gauge will make sure the case diameter has been reduced enough to chamber.

Bottom line I use the Hornady gauge for measuring fired cases and setting up my dies and measuring for the correct shoulder bump. The JP Enterprise gauge is cut with a finish chamber reamer and used mainly to insure the reloaded case will chamber. (plop test)

So the shoulder bump for the AR15 and semi-autos is .003 to .006 and the case body diameter should be .003 to .005 smaller than its fired diameter after full length resizing.
The resized body diameter of .003 to .005 smaller than its fired diameter allows the case to spring back from the chamber walls for reliable extraction.

Shoulder bump figures and sized case diameter from Glen Zediker "Handloading For Competition - Making the Target Bigger. (reloading for the AR15 and M14/M1A)

 

[meathook]

Sounds good

 

[Kryogen]

yeah, once I'm done shooting those 2500 reloads, I'll get the headspace gauge and measure headspace for both rifles and adjust the die accordingly.... that batch was just done with firm contact, but I know that I'm probably resizing too much.

Some of the rounds were definitely fired in large machinegun chambers because 1 out of 30 or so was definitely harder to size compared to the rest.