Marlin 336 misfires

[ba_50]

I've got a 1968 336 in 30/30 that looks like new although I have put about 300 rounds through it. It misfires with either handloads or factory ammo. It leaves light hits on the primer.

The rear firing pin, bolt spring, and mainspring were replaced. They were out of front pins but I don't think that is the problem.

I smoothed up the bolt spring, firing pins, rear firing pin chamber, bolt, feed ramp, anyplace there might be drag. The bolt sat in Hoppes #9 for 3 days and cleaned using a bristle brush and drill. I put the original rear firing pin back in since it was tad longer than the new one. A pipe cleaned was inserted in the front bolt holes in case there was any thing on the firing pin ramp.

As far as handloads, CCI primers were the worst but the other brands misfired too. The primers never misfired in a R77. I picked out the thickest rimmed casings, neck sized the case to headspace off the shoulder instead of the rim. Put spent primers in partway and closed the bolt and the headspace seemed ok.

A different lever was put in with same results.

It's been a while since messing with it but I think that about covers everything. I won't be able to do anything with it for a couple of weeks but thought I would post this anyhow, especially considering JS's help in my last post.

There is a light resistance when pushing the firing pin by hand the last fraction of an inch.

Anyone have any ideas? Figured a gunsmith was next.

What od you think JSCandale?

Thanks.

 

[chuckbuster243]

You dont have a hammer extension on it do you?? It will make mine misfire with CCI's almost all the time. But it has some weak springs and I have not had a chance to change them yet. Check the headspace first and formost. I am sure you already did that I just wanted to make sure. The hammer extensions will slow down hammer fall just enough on some rifles just to not make them fire. Matt

 

[tazzman]

You have mentioned 'a light resistance when pushing the firing pin by hand the last fraction of an inch'. Is that resistance felt when only pushing on the front firing pin, or when pushing the entire firing pin assembly(rear, spring and front)?
Have you been able to identify where that friction is with regards to the firing pin and where it is held?
If there is a restriction in the fit between the firing pin and the bolt?
Is the firing pin hole concentric with the firing pin?
What firing pin protrusion do you have? It should be 0.050"-0.055". If not, maybe your rear firing pin is too short or your spring is damaged.

Phil aka tazzman

 

[ba_50]

Yes I do have a hammer extension on it, but there are plenty of them being used so I doubt if that is the main problem.

I pushed on the rear firing pin. Can't tell you how far it protrudes, but it looks like plenty just eyeballing it.
The bolt spring was taken completely out once but didn't help.
The firing pin hole is round and I don't believe it was hitting. If I remember right, the front pin moved freely.
I put in a new rear firing pin which didn't help. The original was actually longer and was put back in.
I don't know what is causing the drag, yet. It is hard to believe it would slow the firing pin movement that much.

 

[trader steve]

either pin is to short or you have a burr some place there is friction in there if all springs been replaced need to break bolt down all the way,take a Qtip and slide up down where pin runs see if any a Qtip gets caught also maybe a burr so lite you cant see.

 

[mikegaiz]

My money says you have a firing pin problem. I had the same problem on a gun a while back. Went to Federals, CCi are harder cups. Finally replaces the spring.
All better now.

 

[chuckbuster243]

I thought he said he already changed the springs? As the others have said you got a pin problem or something slowing down the hammer... Matt

 

[jonbearman]

How about the hammer spring.I had one that was weak.Now I see you replaced the main spring.Where did you get your springs as some replacements just plain suck.

 

[xs hedspace]

I had a 45-70 Marlin that did light hits, misfired sometimes. Added two washers behind the hammer spring, fixed the problem. Check headspace.

 

[ba_50]

The rear firing pin, hammer and bolt springs came form Midwayusa. I don't think I could get any washers under the hammer spring, as it was tough enough just getting it in.

The q tip sounds like a good idea.

I asked a company who makes one piece pins about it and he said he wouldn't guarantee it to work. He thought it was something inside the bolt.