Marlin jam question

[greenmntranger]

I've done a boat load of reading lately about the dreaded "Marlin Jam". Everything I read has the jam occurring with the lever jammed open. I have recently been experiencing an intermittent jam on a JM 336 chambered in.35 Remington with the lever closed, locked up solid requiring a ton of force to open it up again. The rifle functions fine with Hornady Leverlution ammo but jams with Remington core-lok 200grn.
I have taken it apart, thoroughly cleaned and reassembled as well as made sure all screws are tight

Any suggestions would be greatly appreciated

[Gofaaast]

Is the bullet engaging the rifling? My boolits cast with soft lead expand in the nose during sizing and I experience this. No issue with copper though.

[greenmntranger]

I don't think so, doesn't seem to be any deformation of the lead.

[Gofaaast]

Use a sharpie marker and color the bullet starting at the shoulder and continue coloring down to the shoulder of the brass. Do this with both bullet brands. Chamber both rounds, eject then inspect the core-lok for tight spots vs the Hornady. Your brass for the core-lok ammo may not have the shoulder pushed back far enough if no tight spots are found.

[georgerkahn]

First statement: I am NOT a gunsmith!!!! With that (phew!) out of the way, I had experienced the jam you mentioned in a Marlin I had. After a (too costly) trip to a licensed gunsmith, he answered my question as to what caused it as "overall case length". I was shooting my cast bullets in loads which had a total overall case length just a smidgeon and one-half (technical measurement) too short -- causing one of my cases -- not the first I loaded/shot that day -- to get stuck causing the jam. Note, too, I was not present during the repair -- but, am passing on what the gunsmith who executed repair advised me. I used a Quinetic tool to tap out, and then recrimp cartridges left, which I had not fired, and -- with the new, longer case length, had no further problems.
geo

[earlmck]

The good news is that you are not experiencing the dreaded "Marlin Jam". You probably have a minimum spec chamber and some Remington ammo that is maybe out of spec on the max side and the strategy suggested by Gofaaast will show you what is going on.

The "Marlin jam" occurs (lever open) when the carrier on the rifle doesn't rise quite quickly enough in the cycle and so allows a second cartridge to get slightly onto the carrier along with the one which should be there. There are at least two good ways of correcting this condition (bend the carrier up slightly, or add a little metal to the correct spot) and one half-assed way (make the ammo the exact length so it can't fit a piece of the second cartridge on the carrier).

[grantharris1945]

I had a 336 that I had some intermittent feeding problems with


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