ERGO GRIPS - Pistol Caliber Carbine Spacer 9mm Aluminum Black

I removed the 12 quarters from my AR9 buffer tube (Receiver Extension for you technical types). Comparing this spacer to a dozen quarters stacked on a flat table, this spacer is ever so slightly taller than the stacked quarters. But they’re pretty close! The carbine spring is obviously under more tension if using the quarters because the spring is compressed and under tension because the quarters are taking up that space. In contrast, using this spacer, the buffer spring slips over most of this spacer. It’s a rather clever design. I’m going to run it for a while. I don’t anticipate any issues.

Allows use of standard length pistol caliber carbine buffer. Cheaper than extended buffer. Limits bolt stroke upon recoil.

Works. Drops in easily into a buffer tube. Compresses the buffer spring an inch or so. Supposedly shortens the stroke of the bolt, so it doesn't slam into the bolt catch quite as hard and reduces likelihood of breaking the bolt catch and having to replace that nightmare of a roll pin. Probably also slightly increases the spring pressure/bolt return speed. Way cheaper than Spike's equivalent, and it's aluminum so it should last as long as the gun (not sure I'd trust a $10 plastic version).

Product does what it says. Installed in a 9mm FM-9 PCC lower. Definitely saves the bolt catch because the bolt travel is limited and wont engage with this spacer installed. Fine for the backyard plinker but useless in PCC matches.