Hey Nathan, im Riley Decker from your forum, i will send you a PM in a bit.Hi guys, please excuse my metric and mixed units.
I built a 7mm-300 (7mm Practical) on a Howa last year for a client. The magazine box is 91mm but for smooth feeding from the mag, max COAL needs to be no more than 90.2mm. Divide by 25.4 for imperial.
OK, so I took a gamble with the above and we set the rifle up for a max COAL (touching the lands) of 91.2mm, then seated the A-Max to 90.2mm for 1mm (40 thou) jump. It worked and the rifle shot well. Pet load was 3215fps from a 26" barrel.
I chose the 40 thou jump because if I had gone any shorter, the client would never be able to use a conventional soft point or SST bullets. I wanted the client to be able to use the Partition if need be. As it is, these bullet designs are at a point where the ogive is in or up against the case mouth.
There is not a great deal of difference between the max COAL of the A-Max versus the max COAL of the Berger- Berger tend to run about 20 thou longer.
I have to admit that I do prefer to work with a longer mag box. 92mm is a good minimum (3.622).
As for new generation heavy 7mm bullets, I have been playing with the 190gr Matrix in my rifle, video and autopsies here if anyone wants a look:
Long range hunting with the 7mm 190gr Matrix bullet - YouTube
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