brother mac & seamon, thank you for your advice. i have been surfing for gbb info. a few days, it seems to me a reasonable gaming gbb should be around 2-3k (not include external/outlook parts, that depends on your favor; scope; mounting, etc.).
by far agm is a good selection. since only specific brand parts fit with specific gbb manufacturer, so what are the parts that is a must for agm upgrade (e.g.: hop up, aeg tube, anti-rotation!?, & upper, etc) and what are some of the recommended brand for such part (best with approx. $).
also i heard for the gas magazine, do replace the valve to avoid gas leak.
thx
