As a curiosity, why exactly does one need to empty a 25-30 shot mag in 30seconds
ITT, Infantry Trophy Match, Rattle Battle, what ever you want to call it, only you get as many rounds off as possible in 50 Sec.
Winning gets you the "Dogs of War Trophy"
You have an 8 man team, six shooters and two coaches with binoculars. You're divided up in two fire teams and have a bank of 8 targets. Each team gets four, (3 shooters and one coach).
The Team is issued 384 Rounds. You fire for 50 seconds at 600 yards prone, move to 500 and shoot setting, in 50 seconds, 300 yards setting
then to 200 yards standing.
You get 6 points per hit at 600, 5 at 500, 3 at 300, and 1 at 200 yards ( I might be a little off on the points per yard line).
You also square your targets for bonus points, meaning for ever target with 6 or more hits you square it. If all 8 targets have more then 60 points, its 64, 6 targets with 6 or more, is 36 etc etc.
Notice the more hits you get at 600 the more points. A good rapid fire technique is mandatory.
Also in service matches you have a 2 mile run before you start shooting.
OK Now that answers the question of WHY.
Now to the OP's question. I've shot a lot of rapid fire with gas guns, both in the rapid fire state of HP and the ITT match. Bypods, monpods bean bags, etc don't work. You roll around, the gun bounces around, it takes too much time to get back to your natural point of aim.
What does work is a good solid (sling) position. Tight sling so you have to force it in your shoulder. You cock your right knee up, almost touching the right elbow (right handed shooter). The Left, support elbow is nearly directly under the elbow. (do not grip the stock with the support hand, just let it rest on the hand). You also don't have a 'heavy" grip with your shooting hand, A firm hand shake grip will work. The heavier the grip on the pistol grip of the rifle will cause movement of the whole rifle when you move your trigger finger.
With this position, get a good spot weld, Head straight, chip monk cheek on the stock. You fire, you automatically fall back into position after recoil, back to your natural point of aim.
I've never been able to do this with bipods, or any sort of rest for the rifle. (bags fore and aft, etc).