Originally Posted by redneckclimbing
I have drawn up a reamer for Mr. Kiff but am needing some suggestions on some things I didn't really know. (the question marks on the print)
I'm new to reading these prints too, but I think the question mark boxes are for the throat angle and length (they are geometrically dependent on each other so, technically, it should only be necessary to provide one or the other of the values). The first question mark box is for the throat angle extending into the rifling (the taper that begins after lead section, which is straight in most chambers).
Downloading the prints from SAAMI, I see that the throat angle is 1.5 degrees (1 degree, 30 minutes) for the WSM cartridges and 1 degree for the 7mm SAUM. The second box that your marked with a question mark should be the length of the tapered throat section that ends at the fully rifled bore. SAAMI prints seem to specify only the throat angle and not the length of the angled throat section.
My latest results look good for short-chambering in 7mm WSM by 0.20" and modifying a full length sizing die to push a 270 or 300 WSM case shoulder back 0.162, if that much push back can be done cleanly. Quickload says it should slightly outperform the 284 Shehane and achieve 2950 to 3000 fps from a 28" barrel. I'm not so much interested in efficiency (requires 2.5 to 3 grains more powder than the 284 Shehane to match the same velocity with heavy bullets) as mag-feeding and more easily manufacturable brass.
I don't see much interest in this thread so I might need to move to another forum. I certainly need to run my ideas past people more expert in the art than I!