Yes, I abandoned this thread. How dare I not immediately get on the computer once I woke up?!
Anyway,
http://www.ammo-oracle.com/body.htm seems to be working right now. It's a very good site, explaining the differences between .223 and 5.56 and then explaining the differences between all the different kinds of military 5.56 rounds.
Xargos, the tumbling myth got started because the bullet used to tumble, but not necessarily in the body, nor on purpose. Just as much as hand loaders can adjust the bullet size and amount of powder to tune the loading to the specific gun to get a more accurate load, you can go the other way and get an inaccurate load.
Not counting the wrong type of powder used, the lack of cleaning kits, and poorly made barrels... The bullets used in early vietnam were detuned (though inadvertently) to the M16, resulting in wildly inaccurate bullets and sometimes resulting in the bullet tumbling in mid air causing them to be even more inaccurate.
Only after thousands of US troops died after their M16's failed them in multiple ways did the government issue cleaning kits, issue new m16's with better bullets, and fix the bullet.
But onto the topic of butt pads... Recoil of most fire arms hasn't been too big of a problem for me. The garand, any 12 gauge, the 91/30 and the 1903 were all relatively easy to shoot because I focus on the target and do not worry about the recoil.
However, the MN 91/38 carbine hurts like a ***** if I don't have the butt perfectly in the right place, and perfectly up against my shoulder. Even if I do have it perfect, it still hurts.