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Model 12 cartridge cutoff

Four Fingers Fred

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Hi folks,


Hi folks,


I just got a model 12 and i have a problem: the cartridge cutoff doesn't always stop shells from getting out of the tube when the slide is pulled back, causing a jam. I did a thorough cleaning. It looks like the cutoff isn't going down enough to block the shells, although it could pivot further. Any input? Is there a way to fix that or do i need to change the part?


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This is one of those problems where it would be nice to have the gun in-hand before offering ANY suggestions.


But, fools rush in, and here I am...


The shell stop is easily installed incorrectly.  I've done it many times.  Note the following:


1. The area where the stop contacts the receiver is large -- like a big bearing surface.  This area must be clean and generously oiled.  I use zero weight Mobil 1, YMMV.


2. The forward end of the stop has to go BEHIND the magazine "extension", the very end of the magazine that protrudes into the receiver.  You kind of have to install the stop in a two-stage movement where, first, you get the tip down, behind the magazine tube and, then lay the stop into place onto the receiver.  You can check for smooth and complete movement of the stop at this point.  If good, then carefully complete the rest of the assembly without disturbing the stop.


Hope this helps.

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If the Cartridge Cutoff is not installed correctly if will not function properly. The receiver is slotted and recessed for the Cartridge Cutoff to cycle correctly.  The forward end is inserted into the recess of the receiver.  I get M12's in the shop from customers that have incorrectly installed the cutoff and their guns will not function properly. 
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[glow=blue,2,300] It looks like the cutoff isn't going down enough to block the shells, although it could pivot further. Any input?[/glow]


OK, you've described the action of the cutoff as if gun is upside down.  Directions on a firearm should be written as if gun is upright and held ready to fire.


The cutoff only is active during the part of the cycle where the lifter is raising the first shell up to the chamber.  While lifter is doing that, the cutoff tip RISES so it sticks out onto the base of the (second) shell in the mag.  Otherwise, during the rest of the firing cycle, the tip of the lifter holds shells (mostly) inside the mag tube.


The amount of movement of the cutoff tip on a fairly new (1950s) M12 of mine from fully down (with action closed) to fully up (blocking the shell) is 0.120"  If you don't get half that much movement, the engagement nub on the bottom side of the cutoff where cutoff is pushed down by action slide lock arm opening is worn or damaged, or the nub on the back end of the cutoff is worn, thus preventing enough force being applied to pivot the cutoff.


Find a buddy with a M12, compare how the tip of the cutoff is shaped, to your part.  If sufficiently worn or bent, a cutoff fails to hold shells in mag tube, intermittently.  If the tip looks good, then check the back-end nub of the cutoff that pivots the cutoff - that area may be bent or worn.  Installing a new cutoff may be fastest way to check this.


Nu-Line Guns in Missouri has cutoff's for M12 12 gauge:



As does Midwest Gun Works



Both are $40.


Good luck, GJ


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