Uh... I've got a 9.6V 3700mAh in my CA33E stock, which is almost the exact same size as an MP5 stock, without any modification. An AK will however require a very cell unique arrangement for a 9.6V to fit without modification.
Also, a 2400mAh will put more wear than the 1700mAh. It sounds stupid, but the 2400mAh will have a higher ROF meaning more wear on the mechbox, and will increase wear on the electrical system, including motor. My 3700mAh makes my gun run MUCH, MUCH faster than a 2500mAh 9.6V.
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