I have all of the Smallest / WST Dinobots. Swoop came with the missile launchers or all the Dinobots. It never says which launcher fits with what Dinobot (well except Swoop which is obvious).
However I have been able to find on the internet which launcher goes with which Dinobot.

Now the last problem: where do you put them?

Swoop is obvious of course. Although I had to glue them because they kept falling off. Since I have a 2nd Slag I gave him the gun of this Slag so he can hold a gun in robot mode.   Although I do display him in dino mode mostly.

With Slag I figured out it fits on the side of his shoulders in both robot and dino mode.
With Snarl I found out it fits on the shoulder in robot mode (which are the rear legs in dino mode).
But I can't seem to find where the launchers of Grimlock and Sludge should go in either robot or dino mode.

They do fit in their hands in robot mode. Is this the only way they can carry it?
I find that a bit odd as the 3 others are able to place it elsewhere which allows them to hold all their 3 weapons at one time.

Perhaps there is a place I overlooked?

If you have the original Dinobots you can reply as well as these appear to be nearly identical.