I have a Tufflight Terminator that fly's very nice and turns on a dime but due to it's deep chord it doesn't want to do tight loops. It is a flying wing with elevons. I also have a new Predator X with a much smaller chord that loops and turns on a dime. So again the question is can I do anything to make it loop tighter?

move the c/g back, its probably nose heavy

I tried that. It ended with the first test of crash survivability. It passed the crash test fine but did not like the CG back.

then you set it too far back, c/g on flying wings is pretty sensitive. 1/8" can make a BIG difference...

If you have dual rates on your TX. try increasing the elevator rates on high by about 10% . Get your plane a few mistakes high and start pulling loops. If it doesn't snap stall to either side, the nest time you take her up set your low rates to the high rate level and ove the high rates up another 10%. step it up like that till you like it.
Remember, if your CG is close to its aft limit, when you hit the limit of elevator deflection the snap to one side or the other could be pretty violent.

I agree about slowly increasing the elevator until it snaps out, of course that is the limit. There two other thing I do to increase turning. First is weight, every 1/2 ounce makes a noticeable difference, of course this is best done in the building faze. Second and the only thing left to try is to get the iron out and with a weight on the left wing and the right hanging off a table, twist the right wing with one hand CLOCKWISE and iron the wrinkles out of the outer 1/3 of the right wing. Then do the the left wing COUNTERCLOCKWISE. This will create wash out and allow the wing tips to stall at a slower air speed. Try to be sure both wing tips are the same amount of twist for max effect. Good luck.