04-23-2014, 06:04 PM
My problems with the .270 and .284/7mm bores is that you have to go heavy to get BC, which means recoil and action weight. It's the point where you have gone slightly over the happy medium where everything comes together, and that point is at 6.5mm, and I was raised on .270 with a very high appreciation for it over .30 bore garbage. Imagine my disappointment during Sniper training when I first watched a 173gr M118 Special Ball cartridge fly downrange in a very high arc of trajectory, which literally appeared like a rock being thrown at the target.
For example, the 7mm's need about 10gr more in bullet weight to achieve the BC's that 6.5mm have. A 139gr 7mm classes in with your legacy 129gr 6.5mm's, and 154gr 7mm's are comparable to the 6.5mm 123gr Scenar. What's the difference in recoil between a 154gr 7mm at 61,000psi and a 147gr M80 at 58,000-62,000psi?
For these reasons, both 6.8mm and 7mm are over the edge, unless you're talking about a heavier weapon with a longer action. The 1950's British .270 and .280 cartridges fell somewhere between a battle rifle and an intermediate cartridge, leaning heavily to the battle rifle side. It would have been better than 7.62 NATO because of soldier's load and BC advancements for DM's and LMG's, but is a bit much for maneuver-oriented dismounts, especially considering the space that magazines take up on the soldier.
For example, the 7mm's need about 10gr more in bullet weight to achieve the BC's that 6.5mm have. A 139gr 7mm classes in with your legacy 129gr 6.5mm's, and 154gr 7mm's are comparable to the 6.5mm 123gr Scenar. What's the difference in recoil between a 154gr 7mm at 61,000psi and a 147gr M80 at 58,000-62,000psi?
For these reasons, both 6.8mm and 7mm are over the edge, unless you're talking about a heavier weapon with a longer action. The 1950's British .270 and .280 cartridges fell somewhere between a battle rifle and an intermediate cartridge, leaning heavily to the battle rifle side. It would have been better than 7.62 NATO because of soldier's load and BC advancements for DM's and LMG's, but is a bit much for maneuver-oriented dismounts, especially considering the space that magazines take up on the soldier.