Ok, then I think I may cut down the maverick spring. The AT doesn't catch at all with it on so it must be too long.
While the AT and Raider are fairly similar blasters, I would suggest making a power stock specific for the AT. Chances are if the AT is priming and not catching, the spring might be too long. If it was a matter of strength and not length you probably would be able to prime it to the point of catching, only it would force it right out. And then you have a bigger problem of a snapped catch plate.
Edit: I also only want to use the power stock on the AT. I just got the Raider for the drum and Stock. Alpha Trooper is better than Raider.