Longrange, just noticed your question. The seating die was reset to seat the smk bullets .020 off the lands. I only adjusted the die to seat back to 3.291 when I reloaded the new amax. Had I not adjusted for smk I assume I would have noticed the difference when I seated the first amax.

I did test some bullets this evening. I had 2 lots of 178 amax. I measured from base of the boat tail to the ogive on the bullet (bearing surface, less the boat tail in the back). All rounds from each lot were within .001 of their counterparts from the same lot. With 30 cal insert the difference between lot 1 and 2 was .007. With 28 cal insert the difference was .003, same bullets.

I also remeasured the overall chamber length in my 260 with the 140 smk and amax with hornadys oal tool. Got the following measurements from 5 bullets from each lot.

140 Amax
1) 3.282
2) 3.284
3) 3.275
4) 3.287
5) 3.276

140 smk
1) 3.350
2) 3.350
3) 3.350
4) 3.350
5) 3.349

This again was the total length from casing base to ogive on bullet with oal tool and 25 cal insert on an rcbs dial micrometer.