My friend sold me his bushnell red dot #730134 (pic here) that he had it mounted on his airsoft M4, but the rings are so short that he had to cut off the FSB. I dont have my rifle yet, but I'm hoping to use the red dot for range practice and I'm definitely not cutting the FSB. I'm thinking of YHM 1/2in height rail rasiers in either .75in, 1.3in, or 4in lengths. Are there any taller rings or mounts that I can use? The scope body is 30mm.

Check out the Yankee Hill 5" extension riser.  It is of a cantilever design and will get the scope forward where you need it.  I always keep a couple of these on hand.  I also use the Warne high rings.  This should put the scope right where it needs to be.  If it isn't high enough for you, you could look at the ultra high rings, but the combined cost of those and the riser will put you close to what an ADM mount will cost.  The high rings are cheap at around $30 a set and another $40 for the extension riser.

Good luck.

You can probably get by with x-high rings.  Or , you might contact Primary Arms.  I think he has a good price on cantilever mounts that he could set you up with.