There are two separate files you need to change and I cannot remember which ones they are but if you google increase weight limit (or change weight limit) + STALKER (or Shadow of Chernobyl) you should find someone's guide on how to alter them. With ammo for all three and all the other supplies I want, that sucks up about 35-40 kg of capacity. I understand your desire to increase carry weight, my personal preference for a combat load in the game is completely unrealistic in the real world but in STALKER it suits me perfectly - assault rifle, semi-auto shotgun & VSS sniper rifle.