Originally Posted by
OlongJohnson
All these quotes are from another thread that went off the rails and got hijacked with O'Connor talk and such. Put it here because it's a follow-up to my earlier comments on 7RM.
Ironically, I spent some time playing with load data and a ballistic calculator last night. Looking at the 7RM, .284 Winchester, .308, and .260. After I was sure I had my head around it, I thought, "You know, why don't I just take a look at .270, because I never really have?" So I looked up BCs and load data and put it all into the calculator. Laid the printouts on a big empty table.
7RM is definitely for sale.
If I decide in the future that I should have something longer-legged than the .308 and .260, it will almost certainly be a .270 Win. In a nutshell, it launches the same weight bullets at about the same speed as .308, but they are skinnier and have better BC for a given level of aerodynamic development. As a result, the .270 is clearly and convincingly better than the .308 past 300 yards in drop, wind drift and retained energy. The difference in recoil should come down to just the 15% +/- greater powder charge and its "rocket" effect when the tube is uncorked. Not a big deal. Case neck is ~0.10 inch longer than the 7RM and .284 with less powder burned, so barrels should last notably longer. Shoulder angle is very shallow, so it should feed like Cookie Monster at the Keebler factory, with the modest penalty of trimming brass a little more often than some other cases. And if deer are hunted where you are, you can probably get factory ammo if you need it.
A 140-grain bullet in the .260 will have a better BC than in .270, but it won't launch as fast, so it starts out behind and doesn't catch up until well past where I'm likely to ever have business taking a shot on game, if it does at all. (I only ran numbers to 600 yards.) And 6.5-06 has a reputation as a throat burner.
Which has all been written before, but it was fun and interesting to churn through the data myself and confirm that little has changed in 96 years.