headspace issue with LMT AR15

[ARAR15]

Hello:

I have been reloading for my Steyr AUG 5.56/.223 for several months and shoulder bumping the fired cases using a Redding die and using a Forster headspace gauge to measure the sizing. Fired brass is a few thou above the upper step of the headspace gauge.The rifle works fine.

Recently purchased an LMT CQB MRP 5.56 piston driven and fired some XM193 thru it. No problems with feeding or ejection. Have been planning on reloading for this rifle too. When measuring the fired brass using the Wilson headspace gauge, it is a tight fit, and with slight pressure the brass goes into the tool with 30-50/1000 above the upper step of the gauge (the rim is left exposed). The bolt (without extractor and ejector) would not close on a Forster 5.56 NATO maximum headspace gauge.

Interestingly the Forster 5.56 NATO maximum headspace gauge will fit fine in the Wilson headspace gauge and projects 5/1000 above the upper step.

Does anyone have any explanation for these findings?
Can the brass fired thru the AR!5 be reloaded without annealing every time (in view of the large fired size)?
Any other suggestions would be much appreciated. Thanks

 

[rcmodel]

Size it, gage it, load it.

You do not measure fired brass in the L.E. Wilson case headspace gage.

You measure re-sized brass in it.

rc

 

[ARAR15]

Thanks! That helps

 

[243winxb]

The "headspace gauge" is inside the "cartridge gage" in the photo. The firearms bolt should not close on this headspace gauge. A sized brass or loaded ammo should fall even with high or low points on the cartridge gage. Best if in the middle. A fired brass may be placed in the cartridge gage to see where it sits. A resized case may not be at the same position as the fired case. Brass springs back after firing. The fired case may also be shorter than the chamber if a reload. The XM193 factory ammo i have shot is loaded very hot & should not spring back much, giving you a good idea of your chamber measurement. L E Wilson >

Setting up full length resizing based off fired cases LE Wilson Preferred Method:
This procedure is advised because of a tendency we have noted the last twenty years of the firearms manufacturers to use larger chamber reamers and to chamber more deeply even for rimless cartridges. We have had fired cases from factory rifles which project well above the maximum step.
1. Check your cases in as-fired condition.
2. If the head projects above the upper step, adjust your die as above to where the resized case drops even with the upper step or a little below. The idea is still to push the shoulder back as little as possible to allow easy chambering. The resized case needs only to drop .002 to .003 be-low the fired case.

http://www.lewilson.com/images/CASE_GAGE.pdf

 

[243winxb]

Annealing

Can the brass fired thru the AR!5 be reloaded without annealing every time

http://www.ar15.com/forums/t_6_42/399729_Range_Brass___Fact_or_Fiction_.html I feel its best left to the factory. Had 100 PMC brass where 96 necks split after 3 loadings. The were annealed before the last firing, didnt seem to help. I guess i am not a good annealer. Some BHM brass is on 8th loading, not anneal, 1 split neck so far. Neck turned using standard RCBS dies.