[Unclenick]

Sorry. I absentmindedly gave you the .308 Win spec as if you had an AR10. So many gas guns, so little time.

SAAMI specs on the .223" was 1.760" -0.020" in 1992, so trim-to length is 1.750" by that standard. In 2001 they changed it to 1.760" -0.030" for some reason, putting the trim-to length at 1.745". The military spec is 1.760"-0.015" IIRC, so 1.7525" would be the nominal trim-to length by their system. Just aim for the middle point in the length spec. I think the best thing is just to use the 1992 1.750" so you have some growth room and are within all three specifications and one and three quarters inches is easy to remember.

The bulge you feel does sound like you are crimping too hard. That's a common result. When you chamber hard the chamber narrows the bulge, pushing the bullet forward and may add some shoulder to the neck that way. Hatcher gave an example of chambering .30-06 in a 1917 Enfield shortening headspace -0.006 just with fast bolt work. A chamber can move brass around some.