Help with Hornady Headspace Gauge Kit

Deltagunner00

Sergeant
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Minuteman
Sep 16, 2011
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Central Indiana
Hello all. I recently received my Hornady Headspace Gauges and would like a little advice on using them. This is the set that comes with 5 different bushings. It connects to your caliper.

Anyway, I know i attach it to the caliper and close the ends against one another and zero. Then I put in a piece of fired brass and measure it. This is supposed to be measuring to the datum line. My quesions is how do I translate or use that on my sizing die? Not really sure what to do with it.

Thanks for any input.
 

Sniper Uncle

Patriot Marksman Trainee
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Minuteman
You take a fired case, and compare it to a freshly sized one. In a bolt rifle you want to have only about .002" difference. Any more than that, you are overworking your brass and setting up for a case head separation. I have read that some folks go only .0015" difference to have even less brass working, i can't say about that.
 

Rthur

Philomath
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Minuteman
  • Apr 16, 2010
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    Not Chicago, Illinios
    Like SU said, measure your fired brass. Adjust your sizing die to give you a datum measurement .0015-.002 less than your fired case.
     

    Sniper Uncle

    Patriot Marksman Trainee
    Full Member
    Minuteman
    Terry, I appreciate this video, but why would you have a die shortened and then raise it up one hundredth of an inch. There is a reason they tell you to cam over in a press, because you take all the "slop" out of the linkage. If you use the same make die and shell holder, they will match. If you use different makes, all bets are off. Then, the lock ring is also to keep the die from turning and be sure to keep consistency. What do you use to do that? I think you have made a lot of work for yourself here that you didn't need to. Also, if you are going to set the lock ring and then work with gaps between it and the base, say for different rifles of the same chamber, a set of shim rings for the die might be the way to go. This way you can screw the die down onto the right thickness shim ring and it will be good. You need the lock ring to contact all the way around to keep from "torquing" the die on one side but not the other and possibly creating run-out. Also, you need the lock ring to be actually "locking" the die so it won't back out during sizing, changing your headspace and making the shells possibly not chamber. I think the plan is good, but the execution is prone to error.
     

    Deadshot2

    Gunny Sergeant
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    Nov 4, 2011
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    The Convergence Zone
    You take a fired case, and compare it to a freshly sized one. In a bolt rifle you want to have only about .002" difference. Any more than that, you are overworking your brass and setting up for a case head separation. I have read that some folks go only .0015" difference to have even less brass working, i can't say about that.

    If you want to work your cases the absolute minimum, take a fired case, re-chamber it and "feel" the bolt as it closes. If it closes well without excessive pressure, then merely take the measurement from that case, set the die so it bumps the shoulder back on all cases to that exact measurement and move on.

    For a bolt action rifle it's not a bad thing to have a slight "crush fit" when closing the bolt. that means that the case is perfectly centered in the chamber and isn't relying on the ejector to center the case.