I was just wondering how you fix jammed guns in this game? They will jam on me during missions, are they useless or can you fix them?

You have to keep trying firing. If I'm not mistaken a merc's stats (which ones?) and gun's condition (?) determine how quickly this will get done.

They jam on a 99% too. With a bad ammo. At least in JA1.

And just in case somebody doesn´t know, to repair, your mechanic needs to have a repair kit ready and will repair (so long the repair kit lasts, as it will be used up during repair) all equipment in his inventory.

AFAIR the mechanic needs to have the tool kit in his right hand, a spare one in his inventory will be used automatically.

No need to put a tool kit in the left hand, as repairing never deplete the tool kit entirely and you can combine tool kits to refill them in between missions. And if I recall correctly, a mercenary will only repair the items present in his left hand and his pocket vest. He'll first repair the item in his left hand, and then proceed to repair the items in the pocket vest, starting from the top pocket to the bottom pocket, meaning if there are equipment you want repaired as soon as possible, put them in the left hand or top pocket. You can stack items you want repaired too, for instance if you want to repair five grenades, you can stack them in the same pocket and once a grenade has been repaired, the merc will repair the second grenade in the pocket, and then the third, etc, until they have all been repaired, before moving to the next pocket.