Can Someone Help me with .223 Headspace?

[Historian]

I just got a Forster full length sizing die to load .223 for my AR. When I position the die correctly (touching the shell holder plus about 1/4 turn), my headspace mic. shows that the case is being sized with the headspace about .007" or greater too short. When I back the die off about half a turn, the headspace comes up to about .002" within optimum. What am I doing wrong? Or am I trying to be too perfect?

Historian

 

[rcmodel]

You are doing nothing wrong.

Most of the time, a sizing die & a shell holder of the same brand are right on when adjusted like you described.

But all dies & shell holders & rifle chambers are not exactly the same. A certain amount of variation in the machining steps required to make them allows a certain amount of tolerance in each operation.

Tolerance "stacking", or getting a minimum die, in combination with a minimum shell holder, coupled with a rifle with a near maximum headspace chamber could result in less then ideal headspace.

What you need to do is try the sized cases in your rifle.
Set the shoulder back only enough so the bolt closes easily on them.

With an AR, I would strip the bolt so ejector & extractor spring pressure are not masking how much effort it takes to close the bolt on a sized case.
Then adjust the sizing die down until the bolt closes easily on the sized cases.

rc

 

[Remo-99]

optimum headspacing is hard to accomplish with mass produced rifles, ammo, etc. that's why there is +/- tolerances.
And only your rifle will be able to tell you what it will tolerate, if it chambers the -.002" size cases without issues, then they are better than the -.007" cases. imo.

 

[NCsmitty]

When I position the die correctly (touching the shell holder plus about 1/4 turn), my headspace mic. shows that the case is being sized with the headspace about .007" or greater too short. When I back the die off about half a turn, the headspace comes up to about .002" within optimum.

Not all chambers are created equal!

Do the cases fit the chamber properly when you back off the die the 1/2 turn?

I would think that a happy medium can be reached at some point in the process, and to satisfy your quest for validation, a case gauge may be necessary for an accurate headspace setting.

NCsmitty

 

[cinteal]

agreed. If you want to experiment a little for the perfect setup (everything done according to directions), try different shellholders . You would think they're all the same, but I've seen headspace variation when using different shellholders to about the extent your getting. Stick with the die manufacturer's shellholder when possible. Other than that, see rc's comment.

 

[Historian]

Thanks guys. I'll check a few of the resized cases with my rifle chamber. I am already using a case gauge and they seem to fit fine right there but I see the wisdom in using the rifle that they are designed to be used in. Thanks again.

H.