few questions on resizing lake city (12) 7.62x51 brass

[elfster1234]

so I picked up 500pcs of once fired lake city (12) 7.62x51 brass for my LMT MWS 7.62x51 chamber..... first and foremost this brass is amazing and nice thick walled stuff..... what ever they shot this once fired out of i'm getting a headspace measurement of about 1.639ish / damn near all the way up to 1.640 before I resize... the brass that comes out of my LMT is usually around 1.631ish, maybe pushing 1.632.... like usual I bump back .004 for semi-auto to about 1.627ish..... now with that being said, does this sound about right to you guys? just would like to get some feedback and to make sure i'm on the right track before I do this entire batch. so far on the test pcs I've been able to easy get the bumped back to about 1.627ish and they trim wonderful in my WFT to 2.005 +/- .001... and work great with my Wilson case gauges. what do you guys think before I go to town on this much brass.

 

[elfster1234]

just for shits and giggles... I measured some of my factory hornady .308 ammo and that shows a headspace of 1.624ish..... and some American eagle 7.62x51 nato factory ammo measured out to 1.626ish.

 

[JRM83]

Everything you've said sounds spot on. I've measured a ton of fired/loaded .308 rounds and my observations are consistent with yours.

Most factory ammunition that I have measured is headspaced around 1.626 (.004 below SAAMI min), I assume for reliable chambering in many rifles.

I own a Remington 700 and a POF P308 where the fired brass measures right around 1.631 for headspace. Makes sizing a bit more convenient that they have pretty close chambers. I owned a CMMG Mk-3 that measures 1.635 on the fired brass.

I bought a lot of 2500 once-fired military (majority Lake City) and most of the fired brass measures around 1.636 to 1.640 (some up to 1.642). I'm going to assume that the machine guns that fired this brass have larger chambers to increase reliability and the violent feeding/extraction process doesn't help either. When you are resizing this stuff make sure that each piece gets resized down to where it should be. In the lot of CBC brass I just finished resizing I had a few stubborn cases that did not resize enough on the first pass through the press, even though the vast majority went through fine. There might be a problem somewhere in my setup or technique that is causing this, but I have seen it happen with WCC brass as well (haven't got into the LC stuff yet).

When I load for my rifles I use the fired case measurement to get close to the actual chamber size, and then try chambering rounds of different headspace dimensions to see what the actual largest case that will chamber and extract is, then subtract .003 from this. For my POF the largest case that will reliably chamber and extract is 1.631, so I size all of my brass right at 1.628.

 

[insight3b]

About normal condition for 1x fired LC brass. One thing that will help you get consistent shoulder set-back during your sizing is to knock out the crimped in primer first. Without knocking out the crimped primer first your decapping pin will knock out the primer with intensity on some and ease on others. Knocking them out first allows the ram to travel at the same speed for each stroke resulting in more uniformly set-back brass. Helps with ALL brass but a must-do with LC brass
Don't forget to change the batteries in your caliper too

 

[elfster1234]

thanks guys! this is all really really good information... anyone else like to chime in here before I size $120 of brass?