I have not tried it. It is my assumption that the recoil cycle of the 740/742/7400 is designed to function in the M1 and M14 pressure curve. Or for the lack of another term the "Sweet Spot." Most off the shelve ammunition falls within the Sweet Spot. Components of the firearm may receive excessive wear if the cycle rate is increased by higher-pressure ammunition.
When we were issued a new lot of ammunition for our duty autoloaders we were required to qualify with it. That way we knew where the ammo shot, and if our weapons would function with it. I can recall one unit showed up with an off brand case of ammo on range day. I have never seen so many malfunctions on the range. The ammo burned dirty and the fired cases stove-piped. I assume that a slower burning powder is used in Light Magnum ammunition and may not burn as clean.
A manufacture would not recommend against the use of his ammunition in a certain type firearm if there were not known problems. The manufacture is in the business of selling ammunition. They also test their ammunition to identify issues.
As a reloader my brother tried loading .280 Rem. ammunition for his M742 with slow burning powder.(H4831) He had all kinds of problems. His rifle would not function properly. He dropped back and tried a moderate burning powder and the functioning problem went away.
