> ...twice as less... Which is not so great, as gas cost must certainly add up down the road and compensate quickly for the mags price?
I own KJW Beretta M9 and can tell you, gas usage is not concern at all. Mag holds enough gas for ~40-50 shoots (so reload every second BB load), depending on outside temperature and rate of fire. Holding a mag in the hand for few seconds before inserting it into gun adds few more shoots.
You want to save on Propane? Lets see how much are the savings.
Well coleman bottle is 5.50$, enough for lets say 30 charges, your cost per charge is 18 cents. You dont do more then 15 mags per gaming day on the secondary, and this is including maybe some pistol rounds. So 8 charges, comes to 1.44$ of propane. You can save a 0.77 cents per game day! And this is maximum.
You know, if you coming to airsoft to save money, you'll better run away as fast as you still can
Anyway, as my opinion, the more propane you spend on 1 shoot the better, thats why everyone want to own gun with blowback action. More gas spend - more realistic and hard kick back.