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Discussion Starter · #1 · (Edited)
I'm pretty sure that this post won't be of much interest to most, but writing it helped me to figure out exactly how the Marlin lever action worked and from that, what was causing failure to feed in my Marlin.

Here's the dime synopsis - the small cam on the bottom of the lever arm does not raise the carrier to the top of the receive to present the round to the chamber. What does that is the lever arm catching on the hook of the carrier rocker as the lever is cycled forward, and then forcing the carrier to ride up the lever arm to the top of the receiver at the start of pulling the lever back to chamber a round. Obviously the actual gunsmiths on this forum get this. But us newbies sometimes don't.


> I think I've figured out my confusion regarding how the Marlin lever action works.
We tenderfeet get referred to an animation of how the lever action rifle works that clearly shows that the "snail" cam on the side of the lever near the pivot bolt is the cam that raises the carrier assembly to present a round to the bolt and the chamber mouth. you can see it clearly in the animation and it's very misleading. Here's a link to that amimation. Watch the animation if you haven't already. It is very clear. It is also wrong. Animation: Firing a Lever-Action Rifle South Carolina Hunting License Study Guide for Online Hunting Safety Course

Swany has corrected that - see his link in this thread
lever action animation MARLIN 336 - Bing Videos

Eli Chaps on this forum has a much better explanation under the title "The Basics of How a Lever Action Works". http://www.marlinowners.com/forum/gunsmithing-sticky-s/46737-basics-how-lever-action-works.html

In it he states that the ramp rides on the carrier and just initiates enough movement to block the next round.

Here's the revelation - he then points to the hook or rocker on the carrier and says (paraphrased) that it is this hooks interaction with the lever that is what raises the carrier (and round) completely to the chamber and then pushes the carrier back down for the next round....."

You can see this happen if you carefully watch the action. The carrier clearly does not elevate the round to battery position until the lever starts back.

This is very important to figuring out failures to feed.

Thinking that it was the lever cam that raised the carrier, I had assumed that my carrier needed to be bent upward so that when the cam raised the carrier, the round would be presented all the way to the chamber. Not true. The lever cam is NOT the mechanism that does this, so observing how high the cam raises the carrier is a total waste of time and totally misleading. well, for me it was, anyway :)

As the lever cycles forward the carrier drops and allows a round to enter the carrier from the magazine. As the lever continues forward, the cam "bumps" the carrier to raise it just enough to "strip" a round from the tubular magazine and set the carrier just high enough to prevent a 2nd round from attempting to enter the carrier.

As the lever is pushed forward, the lever arm moves backward, pushing the bolt all the way to the rear and making enough room in the receiver for the carrier to raise the round to battery position.

The lever also slips past the spring loaded "hook" on the carrier rocker and forces the lever to directly engage the carrier along it's side. Because the pivot point of the lever arm is in front of the carrier hook the next action of the lever arm sliding forward against the hook forces the carrier to slide upwards along the lever arm into battery position allowing the round to be pushed by the bolt into the chamber. As the lever arm goes past vertical in the receiver it's angle changes enough so that it can force the spring hook aside into the carrier, releasing the carrier to drop for the next round.

The point of all this? If your carrier "hook" does not sufficiently engage the lever arm and pops out of the hook before the arm has forced the carrier upward all the way to raise the round to the chamber, you will get a failure to feed. Since you can't SEE this happen, and because nearly every reference I've seen gives the impression that the lower lever cam is what raises the carrier and round to the chamber, you may misdiagnose the problem as I have.

In my new Marlin 336 30-30 this is exactly what is happening. In my rifle, the lever arm and carrier hook do not firmly engage. The lever arm slips past the carrier hook too early (almost immediately) and releases the carrier before it lifts the round to the chamber mouth. Instant jam when slow cycling, near jam when fast cycling causing nose deformation on the affected round.

Now I'm thinking that either the hook is too small, or the lever arm is mal-formed. More investigation is in order. I'm wearing this rifle out just taking it apart and putting it back together again. I'm getting fast at it, however.
 

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Can't say that I have ever had to diagnose a failure to feed of that small magnitude. The only time I had that problem was on a friend's inherited Montgomery Ward Marlin 30-30. It was apparent the spring loaded hook, pin, and spring had never been in place on the carrier from the factory. A new carrier assembly with the hook installed cured it right out of the parts box.

There could certainly be some issue with spring tension for the hook that causes this. My first cure might be to try stretching the spring a little (measure with a calipers before and after) to see if that helps. Since the gun is very new I wouldn't suspect the hook is worn but the protruding nub could be mis-shaped. It's a possibility.
 

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Discussion Starter · #6 ·
Ah well, retired engineer - we tend to fall down the rabbit hole from time to time.

I've cleaned up my post which may make it more readable.
 

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Hey! I like that video. But you see where the round comes up on an angle, then gets pushed into the chamber (pointing up)? That's where the wide flat nose cast & some wide hollowpoints (Deep Curl) 44mags get hung up at the top of the chamber in my 1894. Hornady's XTP are closed enough to slip by that ridge.
 

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Discussion Starter · #8 ·
It is a cool video - but it can confuse you if you are trying to solve that specific problem.
 

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Here is a much better video.
I wish videos were available when I was getting started. But, then again, PC's were about 20 years out at that time :( You Tube is one of the upsides for computers.

But thanks.

On the other hand, I have owned several Marlin levers over the last 40 years, and did the maintenance on several others as the "farm family gunsmith". At least a couple dozen.

Didn't take a lot of skill. I replaced a couple rusty extractors, finished a few stocks, and installed a recoil pad or two. Big repairs were replacing a bent lever from a fall, and disassembling a bolt/firing pin frozen with old oil and goo. Beyond that, every Marlin in the family, and owned by friends, just "worked".

Of the many firearms I've maintained, the M336 is about the simplest most problem free since the matchlock. Just more durable.

But I guess a couple do have a bug. Never saw one myself.
 

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Discussion Starter · #11 ·
Of the many firearms I've maintained, the M336 is about the simplest most problem free since the matchlock. Just more durable.<br>
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But I guess a couple do have a bug. Never saw one myself.
Before I comment on the quality of this particular 336 let me say that I am enjoying the challenge of putting it in order. I'm retired, and it's an interesting task. I'm no gunsmith, for sure, but I'm a curious American and every weapon I've ever owned has been in parts on my workbench the day I bought it so that I could enjoy the mechanical beauty of the machine and come to understand exactly how it worked. This includes Winchesters, S&W's, Rugers, Kahr's, Kel-tecs, Springfield Armory, Remington and the M1A1 issued to me in the Army.

I have always wanted a Marlin lever action, and I admired the ones my friends had when I was younger. They were always fine quality weapons. Unfortunately, based on what is written on this forum and on others, I surmise that Marlin's quality suffered pretty badly when it was purchased by Remington. This surprises me as I have a fairly new Remington shotgun that is a nice weapon inside and out.

I know that what I'm about to say is going to hurt some people's feelings and perhaps I should just keep my opinion to myself. However, I think that this experience is worth sharing.

This rifle looks really nice on the outside, but the inside was an unpleasant surprise. I have never opened up a weapon made anywhere that suffered from the simple lack of pride in manufacturing craftsmanship that existed in this 336. Castings looked like pot metal thrown in worn out molds and barely deburred. The hammer appears to be a minimally finished casting. If it is a forging, then the forging tooling should be replaced. Every machined edge was ragged sharp. It cycled rough and gritty, but I assumed that cleaning would remedy that. Cleaning was a start but it seriously needed final finishing with some parts rejected and replaced with parts in spec. Yes it worked. No it was not a pleasure to handle, and No, I don't have pictures.

Light stoning and filing took off the ragged edges. I left the dimples in the block (so as not to screw with the headspacing) and the dimples and the deepest of the grinding marks in the carrier because removing them would have made the action plain sloppy. The bolt was the best looking part inside the rifle, but the slot for the ejector looked like the center portion of a railroad track. The outside of the hammer looked great but the part inside the receiver looked like it was passed over or ignored during finishing. The trigger pull was crisp, but at an amazing plus 15 to 20 pounds. The exterior corner ends of the trigger were sharp. When I started cleaning up the hammer I discovered that the full cock hook actually had a dent in it - the ramps to the hooks are just ... sad.

I thought that I had discovered part of the problem with the carrier not cycling completely when I discovered that the lever arm was bent about 1/16 away from the carrier (the arm releases the carrier before it reaches the chamber), but fixing that made no difference.

My son, a Marine and a one time range instructor looked at the weapon and asked why I hadn't returned it. The reason is that I'm having fun with it - it's like solving a mechanical puzzle - each thing that I fix improves the action somewhat and leads to the next puzzle piece. Also, I'm enjoying reading the posts on this forum, asking questions and getting answers. And the rifle is cleaning up very nicely as a result of my effort and I'm looking forward to shooting it this fall. When I'm done, it'll be a rifle I'm proud of.

Today the rifle cycles more or less smoothly. The receiver's interior is still scratching the bolt but I haven't made a tool to smooth that better than I have been able to accomplish with a dowel and 600 grit wet or dry yet. If I cycle it swiftly, it feeds. If I cycle it slowly, it refuses to feed the shell into the chamber.

Most of the rifle's problems responded pretty well to simple finishing. The inside works are not embarrassing to look at anymore, but the carrier will still not fully raise the round to the chamber during slow cycle. It'll be interesting to see if the new carrier remedies this.

The bottom line is that, even though I'm having a good time working on this rifle, bringing it up to snuff and sharing my experience on this forum, I would not recommend a new Marlin 336C to any of my friends. One made before Remington's purchase of Marlin, yes. One since then, no. And I guess it's maybe a little naive of me, but I'm really surprised that the writers in the several gun magazines I read every month haven't commented on this decline. But it's possible that maybe, just maybe, my rifle is not representative of what is coming off the line today and is simply a lemon - hey, that does happen, even with cars.

I'm not sending it back, but I do need to call Marlin. The manual that came with the rifle made a point of mentioning that the bolt is matched to the rifle (as part of setting the headspace?), and not to mix bolts with other Marlins. To that end, they state that every 336 bolt has the last three numbers of the rifle's serial number etched onto a flat on the bottom rear of the bolt. My bolt has no such marking. Was this step missed, or have they discontinued the practice as another cost reduction.
 

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Your observations are spot on. There are not many new marlins out there with no issues...be it fit finish etc.

I have a thread going outlining similar issues.

I'm thinking of sending for repair but don't want it coming back worst than it is.
 

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Discussion Starter · #13 ·
I talked to Marlin this morning and learned that my rifle was made in July 2011 - it's been on the shelf a while. Perhaps current production IS better.
Also they have discontinued the practice of engraving the bolt with the last 3 digits of the serial number.

I discussed my failure to chamber and asked the rep about bending the carrier upward and he stated that that would probably fix it, but that if it didn't then sent the rifle to them and let them figure it out. Re warranty, they said that they would charge me for parts that they had to replace if I had obviously modified them, but simple polishing shouldn't trigger a warranty refusal. Good to know.

The rep that I talked to was very cordial.
 
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