Surefire shared some hot footage of a 100 round High Capacity Magazine function test with us. They ran 5 100-round mags back-to-back turning an M4 gas tube into a light bulb in the process. Don’t try this with your own, stock AR, though. They used a heavy-barrel, select-fire milspec Colt with a beefed up gas tube to deal with the extreme heat produced by 500 rounds of continuous fire. Watch it glow. Try this with your AR and you’ll watch the gas tube melt.
As far as the ship date of the new mags, Surefire representative Ron Canfield tells us the company has delayed both models if the HCM to make minor changes to the mags to guarantee they function in the broadest number of AR platforms possible. The new ship date is June 30, 2011.
Tolerances vary widely across the spectrum of AR manufactures and while Surefire’s current design works fine in milspec Colt rifles, it runs less reliably in some commercial ARs.