Re: 270 Allen Mag
The ridge left on the neck, next to the shoulder (a little less than the thickness of a dime) is to hold the case firmly to length (head space) and prevent stretching of the body.
COL of both the 169 and 195 is 3.045" base to ogive using a Sinclair thinger that looks like a hex nut with various caliber holes drilled in it. Which ends up being 3.62 base to tip.
This puts things about 20 thou off the lands.
If I remember correctly Kirby was having problems with reamers at the time mine was made and my throat is a bit tight. Not the neck but, the throat. It seems to make no difference to anything. I also think its throated for the 169. It meets my specks for accuracy and velocity with both bullets. Well, actually it out shoots me.
I may be the slowest guy on the mountain . . . . but . . . . I'm on the mountain!