Home Forums Hunting & Shooting Ask The Gunwriters Interpreting SAAMI drawings - case length

In looking at the SAAMI cartridge and chamber drawing for 270 Winchester, the case length is given as 2.540-.020. I'm not experienced in reading engineering drawings, so does the -.020 mean a tolerance of +/- .020, or minus .020 for the minimum length? Thanks

It means the length should be 2.52-2.54 so2.52 min to 2.54 max.

The former. It's not +/- 0.20".

2.540" would be the maximum length where as 2.520" would be the minimum length. The "trim to" length is typically the maximum length - 0.010", or 2.530".