There's a "big bore" speed loader from Chamber Tactical...I'm going to try one and see.,..$9.50
http://www.chambertactical.com/product/ ... ed-loader/
They also have followers for making higher capacity 450b mags out of standard 5.56 mags...
http://www.chambertactical.com/
https://www.youtube.com/watch?v=Vp3E7lf-WJw
...pretty cheap, too...