I tried your tactical reload technique and it worked like a charm. It does require a fair amount of dexterity and fairly large hands, and under the stress of a fight it might be easy to drop one or both mags and then be unsure which one is fully loaded, lose them in the dark, etc. For those reasons a lot of tactical trainers advocate stowing the partially depleted mag before drawing the reload. Hopefully, however, a tactical reload would be performed during a lull in the action and from behind cover. The tactical reload technique Kruger described requires carrying the mags with the feed lips down, bullets facing forward.
While I was working with the rifle I tried a couple of techniques for quickly slinging the rifle over the head and support arm in order to transition to the sidearm or otherwise free the hands. The typical AR15 techniques don't work too well with the long, heavy M1A - too easy to knock yourself unconscious!
I found the best technique was to slide the left hand back to grasp the front of the magazine where it enters the well. Lift the buttstock up off the shoulder and turn the rifle sideways to a horizontal position, muzzle left. With the right hand, grab the sling about four inches from the rear sling swivel. Lift the rear of the rifle over the head and let it drop over the left shoulder, while letting go with the left hand and pushing the left arm through the opening formed by the sling. The rifle ends up slung over the head and left arm, muzzle down, and you can can keep your eyes on the threat the entire time. If you have Jim Crews' manual for the AR15 entitled "Some of the Answer- Urban Carbine," this technique is illustrated with the AR15.
To recover the rifle, grab the forearm with the left hand, thrust the muzzle toward the target while rotating the rifle to the left so that the muzzle describes a counterclockwise circle. Duck your head to the left and allow the sling to slip over your head. Take a firing grip with the right hand. It is difficult but not impossible to keep your eyes on the threat while recovering with this technique.
My apologies to the lefties out there for not addressing left handed techniques. This is a work in progress and I would appreciate any and all input, especially from shooters with actual expertise, like Kruger.