#1
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setting die for headspace
218bee had a threat about a problem he was having with a case not fitting in his 20 vt chamber.
thought I would post how I set my die for the headspace I desire. if you don't have a fired case this won't work. I use a cylinder with a center hole larger than the case neck. in this case I used a bullet puller collet, but you can use whatever you have. that allows me to identify the datum line and case length from the base to the datum line. once I have that length I adjust the die to size the fired case to .001 shorter. unless you have a case with the head expanded from hot loads the sized case should chamber easily. if it's a little tight I push it back another .001 and repeat the process: fired case. sized case:
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#2
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DocEd always makes me a widget out of the the end of a barrel (1/2" long or so), cut off and chambered with the reamer he used to cut the chamber. Perfect fit on the case. Put the widget on a fired case, measure OAL, set your die and adjust for 0.001-2 thou difference. Done. Works wonderfully.
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#3
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Do the same thing using a Sinclair 'nut' comparator.
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#4
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Pretty much the same for me, except......
......I use RCBS Precision Mics, with different "adapters" for different cases, to measure case headspace. No calipers required.
I also remove the bolt firing pin assembly, while test fitting sized cases to a specific chamber. Kevin |
#5
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I don't move shoulders(bolt gun) until a clean chamber and bolt/brass test show a tighter fit. My 3 custom chambered guns I have the headspace gage numbers for, I size for 0.0015- 0.002 under the gage measurements. Two of the rifles were same barrel(blank) lot and same reamer, the smith cut them nearly identical(intentionally) for me. So I can size and use the brass in either one. With an AR(custom 20p and 17 rem) I measure a handful and set back 0.0025-0.0035 from the longest. I tried under 0.002 but had an occasional fail to go into battery, mostly first off the mag. For my two factory AR's I size 0.003-0.004 under the longest fired brass(223 rem wyde chamber).
Last edited by coyotespotter; 06-20-2020 at 12:26 PM. |
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