Personally, I would prefer to see .257 Roberts, it has a little longer point blank range then the other (non - magnum) calibers in that bore range
The .257 Roberts, 6.5X55, and a lot of other 6.5s, are just about the greatest all-around cartridges ever. Lot a stopping power at 300m and very good out-of-the-box accuracy, just where the .223 starts losing its allure.
Reports from Afghanistan are that the .223 is making reliable hits fired from sniper weapons at extreme ranges, but that the bad guy is not hurt too badly unless it's a head or chest shot. In other words, they can keep shooting back.
Pete Kokalis theory is that in order to get accuracy from the 5.56, they have increased the rifling, so you get a small bullet drill-through at long range, rather than the bigger bullet penetration and expansion you need to keep the bad guy down for keeps.
As a kid, I bought a surplus, as new Swedish Mauser in 6.5X55. On the range, it displayed phenomenal accuracy. A 1" group at 100yards ... as delivered for $54.95! Still have it 45 years later.
Most interesting thing I've found on the subject lately: 6.5mm PPC, or .26 Grendel. More compact than .223, but I'm sure weighs more. This guy claims 1000 ft/lbs. @ 1000 yds, 1.5" groups at 300 yds. in an AR 15 match rifle. I want one.
http://www.competitionshooting.com/pages/708565/index.htm
A little bit too long. I've always lked the idea of a .250 savage loaded for pressures above and beyond what the original lever actions it was designed for could handle, or something on the order of a .25-08 with about a 110-115 grain death pill at rght about 3K fps...
Has the firepower of the 50 cal. without the weight and recoil.
Best sniper round around and will be my next rifle.
Accurate out to 1500 meters. Can enter lightly armoured vehicles and will penetrate an engine block.
Hot damn.
Hey Gunney Ermey..........how about a mail call demonstration?