You can also get the lionheart just after Timber...

You need:
-12 pulse ammo

-4 dragon fangs

-1 adamantite

-- 12 pulse ammo can be accuired in 2-3 ways, but both require the Ammo-RF abbility (ifrit)

-1.- You can do it the very slow and painful way-win 20 elnoyle cards (a few people here and there use them, starting in blamb), and then refining them into 2 energy crystals, which can then be refined into 20 pulse ammo.

-2.- The much faster way is to learn the mug ability (diablos) and increase your average character level with Squall, Selphie and Quistis to at least 30 by the second encounter with the "dream world". There you find monsters called Elnoyels near the end of the place, and they only appear in this one place! Any Elnoyels lvl. 30+ will give you laser canons when muged; after getting 3 you can move on, or you can stay and get more, as they are quite useful (1 refines into 5 pulse ammo, and Quistis learns homing laser from them). Now refine 3 of your Laser Cannons into 15 pulse ammo. {Belhemels very rarely drop laser cannons, so Elnoyels are the way to go}

--You can get quite commonly 6 dragon fangs from lvl. 20 - 29 T-Rexaurs, which can be found commonly in the training centre, and not so much in the forests of blamb.

--Adamantites can be aquired one of 2 ways:

-1.- Refine Minataur card into 10 Adamantites.

-2.- Adamantite is a very common drop by lvl. 30+ Adamantoises, which can be found at a beach close to Dollet, near a forest.

After aquiring these Items, go to the nearest Junk Shop (most likely Dollet or Timber, unless you're in Deling City, then there is one there.) and you will be able to remodel your current GunBlade to the Lionheart even if you have no Weapon monthly magazenes at all!