Sound Effects required

[Peter Webster]

Hi all,
       Can someone tell me of a small, lightweight sound unit I can use to simulate a "twin 50mm machine gun" set up in an Elco PT Boat. It is a 1/35 scale Italeri Kit which I am converting to R/C with twin Graupner 400 motors and 7.2v power pack. I have looked at the Ram units and they don't seem to sound right although I may use these if I can adjust them .
       also I must ad the keel and bulkheads are assembled for the 1/24 P.S. Pevensey
Peter W