The YKMF-5 By Quarter Circle 10

Quarter Circle 10 always impresses me. They’ve taken the legendary Stoner design and mated it with the famed Heckler and Koch MP5. Over time they gradually went from an AR that takes MP5 mags to the YKMF-5. The YKMF-5 blends the aesthetics and handling of both the MP5 and AR 15 into a platform that transcends both.

What Does YKMF-5 Mean?

Well, I can tell you the 5 comes from MP5, and the YKMF comes from Die Hard. Remember, Yippie Kai Yay Mother F!#$*%, well, there—now you know. The YKMF-5 is a rather interesting-looking firearm. Inside, things are pretty simple. It’s a direct blowback gun, but don’t let that worry you. Yes, direct blowback guns have excessive recoil, but Quarter Circle 10 helped mitigate that.

Quarter Circle 10 YKMF-5
The YKMF-5 is an odd duck, but that doesn’t mean it’s bad.

Inside the receiver extension sits their famed adjustable buffer system. You can tailor the weight of your buffer to work with your choice of ammunition. Weights can be removed and replaced to ensure smooth and soft recoil and reliability with every type of 9mm ammo on the market. You can go heavy for those hot 124-grain +Ps or go light for those soft shooting 115s. Whatever floats your boat.

YKMF charging handle
It’s not your typical AR charging handle, but it’s plenty ergonomic.

On the outside, we get a weird amalgamation of AR and MP5. Yep, it takes MP5 magazines, and that delivers that odd receiver cut, you see. On top of that, the handguard looks very M5ish. It comes from Bowden Tactical and gives that German look with seamless integration on a flat-top AR.

Quarter Circle 10 YKMF-5 handguard
The YKMF-5’s handguard makes it a great cross between an AR and MP5.

The muzzle device on the YKMF-5 comes from Dead Air and the brace from SB Tactical. We get a big charging handle on the left-hand side to charge the weapon. It’s vast and hard to miss. You poor lefties might feel a little let down, but you let us down by being left-handed, so… We do get other ambi controls from Phase 5, so don’t feel too bad about being a leftie.

The Wacky World Of Quarter Circle 10

The QC10 YKMF-5 is an odd duck, but it still quacks. The AR market is massive, and it’s also kind of stale. So when I see something new and something odd, I take notice. When it turns out to be functional, I pay real close attention. The QC10 YKMF-5 is downright cool, and it’s shipping now with an MSRP of $1,775.

Travis Pike is a former Marine Machine Gunner, a lifelong firearms enthusiast, and now a regular guy who likes to shoot, write, and find ways to combine the two. He holds an NRA certification as a Basic Pistol Instructor. is the world's Okayest firearm instructor, and a simplicisist when it comes to talking about himself in the 3rd person. Hit him up on Instagram, @travis.l.pike, with story ideas.

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