Well lookie here it's a modified Asymmetric Recoilless Carbine-920 (railgun) from Halo 4. I recommend that you add more modifications and remove more original features from the base model so as to make it into a more personal design. I like the idea though, but it would be better if it fired slugs coated in plasma energy or slugs loaded with explosive plasma charges instead of two separate ammos. Ammo is easier to deal with if there is only one cartridge to deal with not two.
Now, if you use a special "clip"-like apparatus to recharge the magazine's internal cells, that could work. The problem right now is that I don't know if the magazine is even detachable. But of course, it can use two kinds of ammo, but maybe the mag can carry either or, from either type of clip, like an en bloc clip a-la the Garand.