...in 3rd ed (the last edition I played and GM'd extensively in) they had Standard and Gyrojet Plus rockets (the latter being useful against vehicles).
In Run & Gun on P. 26, the following is mentioned:
FN makes a full array of alternate munitions that match up well with their standard counterparts. Jelly rockets (Gel) are awesome
The R&G Errata mentions on page 3 (for
Ammo Specific Called Shots ) that both Gyrojet Tracker and Gyrojet Plus rounds "are not in the book and should be removed from this list"
It would also make sense that the Standard (10DV) rockets were the same availability as the weapon (12F)
For now I'll just get the Standard ones as per 4E until this gets sorted out. Seems like there needs to be a revision of the Errata to explain just what is available as well as give the corresponding prices and availability.