Fixing the dreaded “Marlin Jam”
By Rusty Marlin
How the Action Normally Works:
As the lever is cycled, it slightly lifts the cartridge carrier which allows one shell to come onto the carrier. And the carrier blocks the other shells so they stay in the magazine tube.
The "Marlin Jam" as it is affectionately known is caused by an inherent design/manufacturing flaw of the Marlin lever. The lever has a snail shaped cam surface that goes around the pivot screw. Every time the lever is cycled the carrier bounces on the forward edge of the cam. The forward most edge of this cam is left sharp at the factory (the flaw).
After many thousands of cycles, the sharp edge cuts into the carrier enought so that the timing is slightly changed. At first, you will feel a slight "hitch" when cycling, then the timing will get worse; the carrier nose gets lower in relation to the magazine tube opening so that two shells are allowed to exit the magazine. The first shell comes in on top of the carrier as normal, and the second shell slips past the carrier nose and gets trapped between the top of the carrier and the magazine opening in the frame.
Marlin calls this "letting in two" because rather than letting in one cartridge at a time, the carrier allows two to slip by.
See the cam After the sharp edge was removed.
The bouncing forges a notch into the bottom of the carriers' slide surface and over time (high number of cycles) lowers the carriers' initial pick-up height allowing the rim of the next incoming shell to slip over the front and jam it up tight. Note the notch labeled A in the photo.
Simply changing the carrier out as many repair places do is only a temporary fix at best. The new carrier will get a notch forged into it from the sharp edge of the lever cam and over time will settle downward in the action and again give you the “Marlin Jam”. Following the steps below will cure this problem FOREVER.
The Cure for New Guns
For Coyote Caps Alternate solution
With new guns (less than 50 cycles) you can generally get away with just putting a radius on the forward edge of the lever cam. While this will lower the initial pick-up height slightly, it typically will still be high enough to prevent the dreaded "Marlin Jam" from ever occurring. If your rifle jams you will need to follow the steps outlined above.
Many of you will have guns that jam once and a while but haven't figured out why. You probably have an odd piece of brass or two in your collection. For example the gun might run fine on Starline or Winchester but lock up tight on R-P. R-Ps are slightly smaller than others and this will cause the problem to be sporadic. Eventually the gun will jam on anything you feed it and you will need this fix.
The Fix for Used Guns
Note: This is a good solution to general timing problems
Three things are required to fix the problem. The first two prevent it from ever occurring again and the third retimes the carrier to proper height. Don’t even bother to do them if you aren’t going to do item 2A or item 3.
- 1) Put a slight radius on the front edge of the snail cam on the lever. I use between a .025 and .035" R. This radius spreads the load out from the force of the carrier bounce and prevents the forged notch from reoccurring. You will notice a shiny line will form but it won’t be a notch like before. The large radius also self limits how deep it can forge into the softer carrier.
- 2) Order a new carrier from Marlin. If you do this, you will be done, other wise, read on...
- 2A) Grind the slip cam surface on the carrier to just remove the forged notch.
These two items will make the problem worse until item three is done.
- 3) Bend the carriers' nose up about .05".
Use the heat and bend method described below.
Clamp the carrier in a large bench vice so the pivot hole axis runs vertically. The two parallel faces at the pivot hole end need to be clamped in aluminum blocks for a heat sink. If the heat gets to the plunger spring you will need a new carrier, so the heat sinks are very important.
Heat the neck just behind the front of the carrier till dull red. Position a block of steel (or brass) just behind the shell stop (tang that hangs down in front) and tap the head "up". This is actually going to be parallel to the floor.
Measuring this movement can be difficult. I gave up trying after the first few and now it’s by eye. After cooling try it in the gun. If you went too far the very first incoming shell will jam as the lever is opened; the carrier will wedge it up against the top of the magazine opening. You will need to heat the carrier again and tap it back a touch.
This retimes the carriers' initial pick up height to let one round in and keep the rest in the magazine.
Rusty Marlin, SASS #33284
Coyote Cap's Cure
- Take the lever off and the carrier out, place them back onto the OUTSIDE of the frame using the mounting screws and a piece of tape to seperate the parts from the frame (to prevent scratching the bluing).
- Measure the distance from the pivot of the lever mounting screw to the offending point on the lever (where it contacts the bottom of the carrier) and write this measurement down.
- Then using a flat file or belt sander, remove enough metal from that darn point to make it flat, instead of a point, then low amp wire weld the same area back up beyond the measurement and then file it back down to a large flat spot that will match the flat of the carrier.
- Then weld the depression line in the carrier, (that was caused by the sharp point on the lever), back above what it should have been, then file or grind it back down to a nice flat surface once again.
- What you will have done is to do what Marlin should have done years ago when they knew they had a problem with speed cycling the rifles, (get rid of that sharp point).
Why Marlin has not cured this problem, long ago, amazes me.
But I don't have a welder!!!??
Some folks have used other pieces of metal. They normally grind down the carrier to fit in another piece of hard metal. Some used JB Weld or a similar adhesive to attached hacksaw blades, others used two jig saw blades (with the teeth filed off).
Here's what Butcher John Remington did:
I went one better. I cut 2 strips of jig saw blade. (very hard steel) 1/2 " by about 1/8 " wide and removed the teeth. JB Welded them onto the bottom bottom plate where the carrier hit to keep the carrier up a little. Probably 6,000 rounds through it now and there is barely a mark on the pieces or steel and the problem never happened again.
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Updated on 4/11/2007 By Our Excellent Staff Email:email@example.com