Yep XCR is awesome, I've had mine for not quite a month and more then 2 1200 round crates through it of 7.62x39mm.
XCR Pistol mags are great, available everywhere and if you are lucky you can still snag some old stock pistol mags for $26
As for the 5/30's I haven't seen them anywhere, but I will say I don't exactly go looking for them.
Ya best if you cannot source the 5/30's, get the 10 round pistol mags and throw some magazine body extensions for them.
Currently equipped with a Vortex Strikefire II 1x30mm Red Dot, Blue Force Gear QD Sling Mount, Voodoo Tactical One Point Sling & Magpul MOE+ AR15 Grip.