20181208

reloading 5.56mm with CFE223 and 55gr FMJ

Sounds kinda boring and vanilla, right? 

Lake City never-fired pulldown cases, still have the Uncle Sugar primer.  I miked a pile of them for head-to-cone length and separated them into cases with .003" or less under nominal, and those with .004 or more under nominal, and used these shorter ones for this trial. 

Generic 55 grain FMJ (Hornady?  IMI?  Milsurp?  can't remember) but they've been tumbled in molybdenum disulfide powder in a pill bottle for a few hours. 

Hornady's manual, on the page for 5.56mm NATO instead of .223 or 5.56 Service Rifle, says CFE223 goes max at 27.6 grains  Hodgdon's site says 27.4.  With a 20" barrel, a startling 3200 fps. 

So I rolled 5 each starting there and going downward to 26.6 gr in .2gr increments, so I would start shooting them at the bottom of the charge weights and move up, stop at first pressure signs. 16" Bushmaster barrel.  I should be able to stretch 3050 fps out of that with 55 grainers, maybe? 

Nope.  2826fps. The bolt wasn't locking open until I shot the 27.4 grainers.  Cases come back out with HTC of about .002" over. 

Feedback, people.  Meanwhile I'm pulling all that are left, and starting over.