The BJ-1 carries a mix of energy and ballistic hard points spread across its arms and torsos. The arm mounted weapons are quite high on the chassis, and will allow you to fire while mostly concealed behind cover. The ability to mount Jump Jets helps to offset the low top speed of the 'Mech.
The BJ-1(C) is a Champion BattleMech. It features a modified loadout when compared to the Blackjack BJ-1, but it has the same hardpoints. The BJ-1(C) can only be purchased with (MC), but it does provide a 10% XP bonus. It also shares the same efficiencies as the standard -1 in the Pilot Lab tree.
This model of the venerable Blackjack removes the Jump Jets of the Blackjack BJ-1 in favor of two Small Lasers. Mobility and heat efficiency are reduced slightly, but the design has more overall firepower.
The BJ-1X was the original prototype of the venerable Blackjack. It was designed as a scout hunter, carrying four Flamers and four Medium Lasers. No Jump Jets were fitted on this model. Later changes gave way to the production Blackjack BJ-1.
The Blackjack BJ-3 removes the two AC 2s seen on the Blackjack BJ-1 and replaces them with two hard hitting PPCs. However, this presents a potential heat problem since all of the weapon hardpoints are energy based, similar to the Blackjack BJ-1X.
BattleMech Hardpoint List