7.62x51 is a bit different the 7.72x39.
And their magazines are a bit different then the AR15/16 Ak magazines
My HK 91, M1A/M14 and AR10 magazines are prime ensamples of that.
I was referring to weight difference/similarity between the AR-10 20rnd mags and the AR-15 60rnd mags. One v one in weight, fully- loaded. My 10rnd Beowulf .50cal is a heavy one, too, loaded w/ 425gr HPs.
To carry a vest of those into a battle or street fight (SHTF) will make you work and sweat.
I know all the calibers. I worked for an FFL for several years and am familiar with their differences. But thank you, sir, for your information.