I have a CYMA SCAR, A&K M4 + CYMA M4A1 (all full-metal), shooting Matrix-branded 0.25g BBs exclusively. I've been using the magazines that came with each gun and have one spare Matrix hi-cap. Note that the magazine that came with the SCAR fits like a $500 gun—zero wiggle—while a Matrix mag in the SCAR has quite a bit of play. As usual, I suspect, both M4s' magazines wiggle a little. I'm currently running hi-caps but I could easily be convinced to convert to mid-caps if that resolves the rattling-BB problem (I'm only backyard-plinking). I saw a magazine spring-mod somewhere which totally solves the problem. But mods aside, which magazines feed the best out-of-the-box, and is this gun-specific? Price is not an issue. Thanks!