GRAW 360 question, grenades?

I notice on some of the weapon choices they list as having a grenade launcher mounted on the rifle . However when using these rifles I dont see any way to fire the grenade launcher mounted on the underside of the gun, just the regular rifle. Nothing is mentioned about it in the manual either. I'd hate to be missing out on a good weapon.

I mean you can always switch to grenades and throw them with your arm, but it seems like certain rifles have the actual launcher, which would be handy, but as above, I cant figure out how to use them or if you just cant.

Great game so far btw. Nice graphics.

alt. fire the gun

Press A long enough to switch fire rate (grenade/ bullet in your case)

Or tap B.

Easy.