Now lets see.
The 308 Win (from Remington web site)
Velocity
Premier® AccuTip™
muzzle 100 200 300 400 500
165 2700 2501 2311 2129 1956 1792
Energy
Premier® AccuTip™ 165
Muzzle 100 200 300 400 500
2670 2292 1957 1661 1401 1176
Short-Range Trajectory
Premier® AccuTip™ 165
50 100 150 200 250 300
-0.1 zero -1.3 -4.1 -8.5 -14.7
Long range trajectory
Muzzle 100 200 300 400 500
2.0 1.8 zero -3.4 -8.6 -24.8 -50.1
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The 308 Marlin Express (from the Hornady web site)
308 MARLIN EXPRESS 160 gr LEVERevolution 82733
Velocity (fps)
Muzzle 100 yd 200 yd 300 yd 400 yd 500 yd
2660/2513 2438 2226 2026 1836 1659
Energy (ft-lbs)
muzzle 100 200 300 400 500
2513 2111 1761 1457 1197 978
Trajectory (inches)
Muzzle 100 yd 200 yd 300 yd 400 yd 500 yd
-1.5 3.0 1.7 -6.7 -23.5 -50.7
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Ballistic Data from Point Blank software using the Nosler Ballistic tip 165gr bullet for comparrison
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Range Elevation Velocity Energy
0 yds -1.50 in 2700 fps 2671 fpe
100 yds 2.72 in 2492 fps 2275 fpe
200 yds 1.35 in 2293 fps 1926 fpe
300 yds -6.71 in 2104 fps 1621 fpe
400 yds -22.42 in 1923 fps 1354 fpe
500 yds -47.84 in 1753 fps 1126 fpe
I haven't owned, shot or even seen the 308 MX, but to me the differences are not worth discussing. The 308 Win has the advantage WAY out there past where most of us shoot, but it is still an advantage, but that, I feel is due mostly to bullet desiugn, not the cartridge capabilities.
As for accuracy, I'd suggest checking the marlinowners.com web site as they have a section devoted soely to this round. all the reports I read show it makes the leverguns built for it appear as accurate as many factory hunting rifles in 308 calibers. NOTE I said FACTORY and HUNTING rifles, not to compare this to any tactical or target rifles in the same caliber.