Here are my 2 Amend2 6.5G mags... Left side shows a Cain Arms +6/7 5.56 extension, and right side shows an Amend2 +5 5.56 extension.
Left mag holds 13, right mag holds 12 6.5 rounds. Both mags hand-feed just fine. ETA: Cain Arms extension needs a shim to tension spring correctly to allow follower to trip bolt catch. No big deal.
The Cain Arms extension is 3d printed and costs $18. The Amend2 extension is machined AL and costs $35.
Left mag holds 13, right mag holds 12 6.5 rounds. Both mags hand-feed just fine. ETA: Cain Arms extension needs a shim to tension spring correctly to allow follower to trip bolt catch. No big deal.
The Cain Arms extension is 3d printed and costs $18. The Amend2 extension is machined AL and costs $35.

