I've got a bunch of the plastic ones from Harbor Freight. They will hold 500 rounds of .556. Catch them on sale with a coupon for $3.99. Sometimes $2.99. Works for me.

LUCK:::; When presistence, dedication, perspiration and preparation meet up with opportunity!!!
- - - - - - - -A government big enough to give you everything you want, is big enough to take everything you have. Thomas Jeferson - - - - - - - -