Originally Posted by
oldsagerat
I lube the .223 cases first with imperial sizing die wax. I run them
into a 300 BLK trim die once, cut the case off with a small chop
saw, trim the case to length on a normal case trimmer. Then
To test if the case neck is thick or thin, I lube the case, run it into
a 300 Blk sizing die. I then seat a .308 bullet and measure the
outside of the case neck with a micrometer. If this is thicker than
a factory round I know I must turn or ream the case necks before
I use them to load up 300 BLK. A tedious but necessary process.
Most 300 BLK formed from military .223 has necks that are too thick. They may chamber in your rifle but there won't be enough
room for the necks to safely expand on firing and this can be
very dangerous to you and your firearm. Just a little FYI.