Why won’t my Mac-11 bolt retract?

[ianian]

I’m having an issue with my Cobray 9mm M11 semi auto closed bolt gun. 9 out of 10 times, when I go to charge the weapon, the bolt gets stuck and only retracts about half an inch.

The feed ramp has some interesting wear which may be causing the issue (but not likely). When I separate the lower from the upper receiver and retract the bolt by placing the buffer plate on the floor, the bolt retracts fine. This makes me thing something is getting caught in the lower.

Any suggestions?

Thanks!

 

[sniperdoc]

Sounds like there may be a part in the lower that is installed incorrectly.

 

[ianian]

Following up on this, when I take the upper off the gun, insert only the recoil rod and spring, and push down on the recoil plate, it’s not able to move forward more than half an inch. So the recoil plate isn’t able to enter the receiver because of how little it travels.

 

[ianian]

With a magazine inserted, it will retract fine but won’t bring the hammer back far enough to cock it. Without the magazine, the bolt won’t retract.

 

[Member13]

If the upper is removed does the bolt slide freely in the upper? If so it may be getting caught on the recoil spring or the ejector spring...or the guide rods of both.

 

[Offmarksman]

Is the guide rod bent? Take it out of the bolt, and roll it on a flat surface. If you can’t roll it, it’s bent

 

[Villafuego]

Is your recoil spring not captive on the guide rod? (the whole assembly should be held to the bolt by a small cross pin)

 

[ianian]

The guide rod is not bent and the recoil spring is captive. After closer examination, I’m able to rack it regardless. However it often takes two hands, with the back of receiver against my chest (not exactly safe). If I had to estimate, it takes around 40 lbs of force.

 

[Offmarksman]

The 3 or 4 of them I have had are hard to pull back. It’s actually crappy design. It was an afterthought to sell some guns after the 86 mg ban. The receivers were designed to be open bolt.

 

[Jmacken37]

Safety on?