Most sandys have them attached to the backpack shoulder strap via nylon webbing and a quick release buckle.
I personally use a 4" piece of nylon webbing that loops around the bell strap and sits between the bell and chest to back strap. The other end fastens to a snap mounted on the ammo pack.
If you want to go sandy I would highly suggest you visit and read the Sandtrooper's CRL - http://www.mepd.net/crl/
The leather ammo pack seller is Blaster 8266, you can reach him at abailey8266@yahoo.com.
NOTE: Leather is NOT required for basic deployment (Police). From the Sandtrooper CRL - #20.AMMO POUCHES: Two or three in total, made of black leather, black or dark green canvas or black vinyl. Worn either at the hips or left shoulder, opposite of the pauldron.
HOWEVER, if you plan on going for S.W.A.T. then don't buy a thing until you researched which trooper you want to emulate being there are many differences between them.
Edit: Since you have a orange paldron (Sandtrooper Captain) here's the page you can see all the different versions - http://www.mepd.net/crl/captain/
Edit, edit lol, if for some reason the Captain link doesn't work just go the above CRL and scroll to the bottom... sorry