Review: Mitchell Defense “Rat Dog” SBR

In a modern world dominated by the 11.5-12.5″ barreled 5.56 NATO SBRs of exceptional performance, the era of the pistol caliber seems relegated to obsolescence. But it’s not a declining obsolescence, it feels proportional. It is parallel to comparable 5.56 and 300BLK offerings, neither closer to them or further from them. There are things the 9x19mm cannot do, there are things the rifle calibers also cannot do. Those key points of difference cannot be made up by one or the other caliber and so 9x19mm really hasn’t declined so much as having been put into an overt niche.

Into that niche we’ve seen a second resurgence of the the pistol caliber carbine. The PCC is full of modern offerings. The SIG MPX. The CZ Scorpion. The B&T APC9. The Noveske Space Invader. The Aero EPC.

And this guy, the Mitchell Defense “Rat Dog” SBR.

 The “Rat Dog” got its name from a SARC (Special Amphibious Reconnaissance Corpsman) who is known to thrive in the suck and stay in the fight no matter how dirty or tired. The whole Mitchell Defense line up is built around reliability. The Rat Dog is no exception. This rifle was designed to be the most reliable and functional PCC on the market. Featuring a two-stage trigger that is built specifically for the PCC and wont break due to increased stress from a blowback gas system. Adding a lipped buffer tube, flat wire spring, and a properly weighted buffer all came together to make an extremely reliable and enjoyable PCC.

Allow me to skip the weighing of capabilities dialogue for a moment, I’ll return to it but there’s a feature I want to highlight foremost.

This little gun is stupidly fun to shoot.

Running a 33rd Glock stick through the MD9 Rat Dog with its Timney PCC trigger is a riot. That ‘feature’ is among the strongest keeping PCCs market relevant. There is something unparalleled in the delight that a 9mm carbine produces that I cannot replicate out of a rifle. My Z5, My Scorpion, and this Rat Dog MD9 all illicit this primally joyful reaction while you shoot them. Whether hammering away at steel or grouping a bunch of hits centered on paper far faster and tighter than you can with a handgun, the Rat Dog slaps.

PCCs are awesome.

Now back to performance.

A 9mm 124gr +P cartridge fired from an 8.3″ barrel could produce muzzle velocities a touch higher than your 3″ to 4″ handgun in the range of 1200-1300 feet per second (fps) and top up the muzzle energies in around 400-450 foot-pounds (ft-lbs). This increased velocity and energy improve the cartridge’s effectiveness in self-defense and other scenarios where external and terminal ballistics need an important boost.

Unlike 5.56 guns, the 9mm guns get most efficient in their SBR personas. Instead of compromising muzzle energy for size savings they thrive as 4.5-10″ barreled guns, allowing the round to accurately reach targets out to 200 yards. It is almost impossible to build a PCC too small. SIG actually tried with their Copperhead, but 3.5″ of barrel is the standard space 9mm powder charges are designed to burn within. The longer guns exhibit very comfortable handling characteristics and add a little more speed onto the rounds. The cost is an additional factor with 9mm ammo having returned to very affordable levels to purchase by the case right now.

The Rat Dog sports an 8.3″ barrel in its SBR configuration with either an MP5 like profile handguard or a modern M-LOK handguard. The tri-lug muzzle over the 1/2×28 threaded barrel encourages the addition of a suppressor and I also encourage its addition.

Being a blowback gun, it exhibits the rather entertaining phenomenon of being louder near the shooter (specifically by the ejection port) than near the muzzle when a can is attached.

The MD9 Rat Dog handles like a svelte AR. It is fed from Glock pattern 9mm magazines, offering a number of feeding options and sidearm cross compatibility. It’s only departure is that the bolt lock is manual only, it won’t operate with the Glock magazines slide stop engagement feature.

Function of the Rat Dog is flawless and smooth, the carrier and buffer system are properly massed for cycling and function. This is the crucial balance of forces making a blowback PCC run and any AR9 is made or broken in this balance. The Rat Dog nails it and the gun becomes a point and shoot interface instead of the a light but violently recoiling mass tossing just waiting to stop on a round trying to chamber.

“But NFA!”

Yes, NFA wait times are a righteous mess. However, I also cannot stress enough that the wait time for getting a stocked gun is worth it.

That said,

You can get it in 16″ ready to run in competitive PCC spaces.

• Ambidextrous safety & charging handle (Radian)
• Glock magazines (D50 time)
• Timney two stage trigger

Let it run and have fun.

Pratical/Tactical

The perks and limits of 9mm carbines are well established. You are choosing a pistol round in a carbine format that modestly increases its terminal ballistic capabilities while vastly increasing its handling capabilities. We aren’t changing the energy profile of the rounds by much, we are changing the hit probability and the off hand maximum effective range. We are also (potentially) consolidating ammunition expenditure between your carry gun and your carbine.

The question then boils down to a neat and simple one, can 9mm do the things you are asking the carbine to do?

Probably.