Well, if you are using a rail bushing, and I assume you are, then you have a rail that is out of spec. I wouldn't go with the scotch tape idea. The sear pin is usually tight as it is. You might be able to press fit a solid slug into the rail bushing hole and drill the hole in it so it is forward of where it normally sits. That would push the valve farther forward.
Originally Posted by factoid
What might work, is if you shave a tiny bit off the inner flat edge of the powertube tip. Its the flat surface that pushes against the carrier. Taking a bit off it will allow the carrier to sit farther forward. Make sure you do it against a flat surface so you don't sand more off one side than the other.
The other option is to shave a bit off the carrier itself. The problem with this option is that it only works on the one carrier. If you have to make a change for any reason, you will have to do it again for the next carrier, and then the carriers won't be interchangeable in other guns.
Except for the Automag in front, its usually the man behind the equipment that counts.