Having ALSO grown up in the military, and served for 22 Army Reserves, and a veteran, what I've learned is that soldiers don't always want what they get, and often don't understand the application. That's why they go to schools, and constantly rehearse in training exercises.
Just like any other team, you don't get to do what you want, you train to do what you NEED. The .300 Win Mag is certainly replacing the .308 - simply a matter of better long range ballistics. It's certainly NOT replacing the 100,000 M16's and M4's in Afghanistan. It's a extreme precision cartridge for the specific use of a highly skilled two man team. And they can both shoot the M16's they are issued for their personal defense quite well.
Question was asked, the most impressive .308 - and answered, the AR10, which is the pinnacle of the design cycle. It's the most accurate, lightest, least complicated, easiest to maintain and service, endures abuse, doesn't need nearly as much maintenance.
Let me expand on that: It's not steel, so the receivers don't rust and deteriorate half as much, if at all, compared to the exposed machined steel action of the M1. The composite furniture needs nothing more than a wipe down, unlike wood that requires some oil as a protective finish to be regularly reapplied. The composite surface resists abrasion and dings with a much higher hardness, and is less prone to cracking along natural lines of weakness.
Any one who's been required to clean and service a Garand piston knows that it's mandatory on a regular basis, more complicated, and adds difficulty to disassembly. The AR10 shotguns, the carrier pulled out, and then torn down simply with no parts needing complex twisting motions to separate. There is no operating rod to suddenly fail and disconnect from the bolt to fly back at the shooter - a known defect in the Garand design. Nor will the trigger mechanism fail to lock into place, falling out into the mud at an inappropriate moment just as rapid fire is desperately needed.
The romance of the Garand has it's appeal, but only compared to the '03A3 it replaced. Just like the Garand, the AR10 offers quite a few superior upgrades that a combat soldier can appreciate, and exactly why they still are, even downscaled in the M16. That's why it's the most impressive .308, as it was the last of the post WWII impetus in design of new combat rifles.
Mechanical designs mature to their zenith, like roof prism binoculars, or the internal combustion engine, the AR10 made the final decisive modification by putting the gas chamber and piston in the bolt carrier. It's the same as sticking the camshaft directly over the valves, or making the pixel on the TV screen self illuminating without the use of a scanning electron gun.
Shooters are an extremely conservative lot, old wood and steel guns like the Win 94 .30-30 sold extremely well for over 100 years. In that same light, shooters would still be revering dial up land line telephones, massive Curtis Mathes 27" color console TV's, and flathead Fords. It's exactly the same thing - and come to think about it, they were impressive in their day.
But compared to cell phones or a twin turbo V6 F150, no, not so much. That's why the AR10 is hands down the most impressive .308 ever designed - and literally the last of it's kind. The proof? It made the transistion to intermediate cartridges, and owns the market in the free world.
