I am going to build a long range hunting rifle in some sort of 7mm. I am set on compmnents: Lawton 7000 SA, 30" Kreiger 1-9 twist, AI stock. My dillemma comes with the 7SAUM and loading 180 Berger's long. (I want to use an AI stock and magazines and obviously they won't work this way.)
I had also noticed that a .284 Shehane will do basically the same velocities but is even a tad longer when loaded long. This got me thinking wildcat. My idea was to take the proportions of a 6mm Dasher and push them out to a SAUM case.
When I did these calcs. I found some interesting things:
- This gave me almost identical volumes to a .284 Shehane
- The start of the shoulder was only slightly shorter than a standard SAUM
So, I thought why re-invent the wheel? Keep the lower (below the shoulder) part of the case the same, and put a 40' shoulder on it. With this combination it should have a slightly larger capacity than the Shehane but not much. This smaller volume should be more efficient than the SAUM or WSM. I am hoping that with about 56 grains of H4831sc it will consistently reach the 3000-3050 fps velocity node.
- This will easily fit into an AI mag. with a 180 Berger loaded long
- with the 40' shsoulder I think that t will give slightly better vels. with similar charges as the Shehane
- With a similar powder load to the Shehane I was thinking that the barrell life should be similar (everything else being the same).
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 was also wondering if someone could run this through QUICK LOAD and see what it spits out.
I also have not had a chance to measure any bullets yet so if anyone knows the bearing surface lengths of some bullets and could post them that would be great so that I can finalize the freebore length. As you may notice this is basically a SAAMI chamber with a 40' shoulder and a slightly tighter neck.
Please let me know what you think!Attachment 6482
Here is a copy of what I have so far.