Just a word about weight, Thompson / Grease gun vs M-14. It's true there's not a lot of difference in the guns themselves. The savings is in the ammunition. On a long patrol it's not uncommon for one of these guys to be carrying 200 rounds of ammo along with the gun. If you ever have the chance, pick up 200 rounds of .45 ACP, the pistol ammo used in the sub guns. Then pick up 200 rounds of 7.62 Nato (.308 Winchester), the fodder for the M-14. I think you'll quickly come to appreciate the shift in weaponry. This was one of the great logistics advantages of the M-16 and its .223 caliber ammunition, less weight for the soldier to carry with the same firepower. Unfortunately, the M-16 was plagued with reliability problems when the Army shifted to a dirtier, cheaper powder in the ammunition. The direct gas impingement system cruds up the bolt and carrier quickly causing it to jam. The redesigned gun has a "forward assist" plunger to force the bolt closed during a jam and some other features to make the action less vulnerable to fouling. The other thing the Army did to improve reliability was to enforce a strict and frequent cleaning and maintenance regimen. While the new generation of soldiers accepts this, a WWII vet would be astounded. His Garand might see a thorough cleaning twice a month in the field. Unfortunately M-16 reliability problems have started to reappear in the deserts and the military is once again looking at a redesign. Interestingly, this one may replace the uppers on the M-16 with a gas piston system ala the AK-47. In the meantime, the M-14 is making a comeback as a more suitable weapon for the long ranges involved. And, like its predecessor, the M1 Garand, it requires far less maintenance.