F5 MFG Modular Stock System (MSS) for B&T APC9

The F5 MFG Modular Stock System is the dedicated adjustable stock for the B&T APC9. Unlike a universal 1913 brace that needs the A3 adapter to mount, the MSS ships with its own 6061 billet aluminum B&T 9mm adapter, so it bolts straight onto the APC9's proprietary rear interface. The stock itself is a telescoping, left side-folding polymer unit that is fully adjustable for comb height and length of pull, which is more than most folding braces offer.

The billet adapter is 922r compliant, and the assembly weighs 10.72 oz without a buffer (buffer not included). Users report a rigid, slack-free lockup and well-machined components, which is the standard the APC9 platform demands. The adjustability makes it a better fit for shooters who run the gun with body armor or who want a precise cheek weld for optic use.

At $299.99 it sits between the cheap A3-adapter-plus-universal-brace path and the $625 to $650 B&T factory folding stocks. Pick the F5 MSS when you want a single dedicated stock with real adjustability and do not want to source an adapter and a brace separately. Pick the A3 adapter plus a Strike Industries folder when you want the lowest-cost or shortest possible setup.