You might get away with a low pressure tank on a level 7 mag with an 11" non-ported barrel. They operate at around 350psi in the front chamber with the perfect barrel length for optimum efficiency. As soon as you put a level 10 on it, even with the gold spring, you increase the operating pressure in the front chamber up to at least 400psi or more, which would require about 600psi to proper charge at rate that would prevent shootdown and chuffing. If you use a longer, stiffer bolt spring the pressure requirement is even higher. If you use a ported barrel, the pressure requirement is higher again, because you are loosing efficiency.
Except for the Automag in front, its usually the man behind the equipment that counts.