[Unclenick]

The actual SAAMI spec is 1.760" +0/-0.020". So anything from 1.740" to 1.760" is within that spec. The long number is to prevent the case mouth going deep enough into the chamber to jam in the throat and raise pressure. The short number is so the smallest bullets made still seats deeply enough in the case to have adequate neck tension on them for magazine feed without the bullet being knocked too far off axis if they are seated within the SAAMI max cartridge COL. Still shorter bullets can be used, but often have to be seated below maximum COL, and the manufacturers usually give you the reduced COL in their load data.

The trim length is usually in the middle of the SAAMI range to allow for some plus and minus tolerance error in the trimming. The fact is there are people who trim much shorter than even 1.740". If you don't crimp, you can often get away with that. The advantage is you can trim the case just once and never have to trim it again within its normal case life because it will just grow to 1.760" about the time neck splits or other wear problems cause you to retire the case altogether.