Lets get these out of the way from the start,
Looks like the SP-1 is a Registered conversion to full auto, so going to guess that there is a tax stamp in the mix.
Next, you really, really suck at shooting full auto, and no way in hell that I would even get in a kill house with you for a match run!!!!
Angle square your back foot back for lower body rocking support, get your shoulders in front of your hips, and lean the fuck in to hold the muzzle steady during the bursts..
You want to absorb the rifle recoil's in your upper body (not rock your upper body back past your hip line), and as the gun recoils your upper body backwards towards your hips, you have the power of your stomach to hold the muzzle on target as you get a slight head rise.
https://www.youtube.com/watch?v=WVJsNKvLk5g
As for the troubled uppers, was the problem with semi auto and full auto, or just full auto instead?
Also, the same M-16 B/C is being used in all the uppers, or do each of the uppers have their own B/C's instead?
If same B/C across the board, we can weed that out, and would be a gas or chamber/head space problem in the upper's instead.
Also, look at the bottom of the Uppers, and make sure that they are Auto sear relief cut and not the problem at hand.
If different B/C's, then need to head space checks, and start to check the gas keys for leaks on top of the carriers.