beemanbeme I thought you were definitely on the right track, in fact when I read your post I said, "Ahhhhaaa that makes pefect sense!"
Until I did compare. I'd tried to upload a pic but it won't let me, says the folder is full and notify administrator. The bullet is way past the bottom of the neck, almost .30 of an inch.
kyote I do have one Lee die for my 25-06 but never used it yet, using the RBCS. I think the Lee came with a crimp? I'd have to dig it out to confirm.
Anyway Winchester and Lee use a similar crimp on the 5.56 which appears to be a six sided crimp. (The pic not the best highlighting what I thought was an unusal crimp I have only found on Winchester factory 5.56 rnds)