You can modify a rifle buffer, EASY. It's 1/2" internal diameter, so you only need a piece of 1/2" OD PVC pipe, to remove a weight, and replace it with a piece of PVC of the same length.
I'm telling you right now, that if that is the case - and you need to lighten that buffer to get it to function... You need to drill up your gas port. The gas port is too small. Been down this road too many times, and know it too well.
Before you do anything to that gun, I'd pull that gas block and measure out the gas port diameter - and post that number in here.
I'm just sayin'... don't exactly know what I'm doin' here, but I'd be drilling that gas port up if it was mine...