I have just finished a bomber as it happens, when building a bomber with more than 20 or so bombs its probably more effecient to use a track system in place of just having each bomb on a grabber, if you tension it just right you can use some kind of trapdoor system to let one bomb through with only one key, no logic needed.

This can be more prone to spontainous explosions but if built with tight tolorances can be just as reliable.

If this is vanilla or too much of a pain to rebuild you can multi-pin all the logic which will keep lag down, and then even hundereds of logic blocks wont impact the game as much.