This is a Magpul Industries Magazine known as the PMAG, model MAG698-BLK.
The PMAG 5 AC L" Magnum is a reliable and durable polymer magazine for .300 Winchester Magnum based family of cartridges and is compatible with long action AICS-spec bottom metal" to include the Bolt Action Magazine Well 700L for the Hunter 700L Stock. Built using M3 technology" this magazine is advanced in both material and manufacturing processes providing an economical" lightweight" durable and reliable single-stack bolt action magazine.
Features:
5RD capacity
Black polymer construction
Self-lubricating follower
Stainless steel spring
Accepts cartridge with overall length up to 3.50"
