For you knuckleheads, the problem is the WT, BULK, AND EXPENSE of heavier guns and loads. The troops don't HIT anything with 999.9 % of the rifle rds that they fire. So why weigh down and bulk up the trucks, trains, planes and troops with heavier rds that they won't hit anything with?
If you are not strong enough or fit enough to carry a heavy gun (don't know at what point a gun is considered heavy), then don't carry one.
If, on the other hand, you are strong enough and fit enough to carry one, then wt is no longer a problem.
Bulk? I guess it depends on how you define bulk.
Expense? Interesting one. You can build a very reliable FAL for far less than it will cost you to buy an AR. You can buy an AR for much less than a match grade M1A1.
That's a subjective call.
Personally, if I were buying a rifle because I thought it would be used to keep me alive in SHTF, expense would probably be the LAST consideration. What is your life worth to you?
We could write a book debunking the myth about missing 99% of their shots. A lot of data is rolled up into this figure - minigun rounds, suppression fire, break contact, etc. It would probably be more realistic to look at the current engagements by patrols in Iraq. From what I've heard, it's more like 90% of the shots are ON target.
Bottom line, you need to decide for yourself, based on a number of factors:
Can you carry / use the gear you've chosen.
Are you recoil shy and have a flinching problem?
can you shoot larger calibers with skill?
bug in - are you planning to ride out SHTF in place?
bug out to a location - do you have a cabin or a secluded spot you are planning to go to?
bug-out and wander like a nomad? nowhere to go, forced to carry everything on you back.
are you planning to initiate ambushes because you don't have any caches of supplies?
are you planning to avoid conflict as much as possible?
Planning to hire yourself out to warlords or planning on working towards a return to society?
I could go on and on, but the bottom line - it's not a one size fits all world. You need to decide for yourself what works and what doesn't.
Also, you really need to try your gear in the field...
Andy, you really need to get some exercise and start working out with the weights. Its beautiful weather, spend some time out in the field camping and hiking. As out of shape as I've heard you are, you'll have a coronary or stroke first day of shtf and miss all the fun.