Back before MT came out (in about 1985 to be more specific) I did much what far-trader did, and designed my own magazine-fed laser weapons (carbine, rifle, & pistol).
I had the following rules:
Belt-mounted powerpack available @ +1 TL (6 hour recharge, weight 1,500/2,000 grams, costs as related backpack powerpack)
10-shot mag @ +2 TL
15 shot mag @ +3 TL
25 shot mag @ +4 TL
Remember, Laser Carbines appear @ TL 8, Laser Rifles @ TL 9.
Cost: 100 cr for carbine mag, 125 cr for rifle mag.
Weight: 400g for carbine mag, 500g for rifle mag.
Magazines are specific to general model (pistol, carbine, rifle).
Magazines are rechargeable, requiring purpose-built charger and access to "high-power" energy source (comparable to 220VAC & 25A or better).
Recharging requires 1.5 hours per magazine, irregardless of capacity or model.
Charger costs 200cr for pistol or carbine, 300 for rifle.
New Weapons:
Laser Pistol: TL 11+; base weight 900g; magazine weight 300g; 10 shots/mag; length 250mm; base price 2,000cr
Laser Sub-Carbine*: TL 10+; base weight 3,000g; magazine - as Laser Carbine of same TL; length 500mm; base price 2,500cr
*developed in 2002 picture a laser version of an MP-5