I bought a used Marlin 45 70 and have experienced some misfires. I tried various things to remedy this problem to no avail. I took the gun to a gunsmith who supposedly was able to chamber the no go headspace gauge (not in my presence) and then said that it had excessive headspace. I finally got around to calling Marlin and they sent me a shipping label. I thought it would go to Marlin but it was instead sent to Williams Gunsite. The guy at Williams said it does not have excessive headspace. So either someone is incompetent or is lying to me. Williams was about to ship the gun back to me but I asked if they would instead send it to Marlin to see if they can figure out why it occasionally does not fire.

I noticed that when pulling the trigger on a fired case the bolt will often move forward about 0.015" which to me seems quite a bit and to me would indicate excessive headspace but I am far from expert in the workings of a lever action. I sure hope Marlin can get it running reliably.

Any thoughts on what is causing the misfires?

Since the .45/70 headspaces on the rim that should be easy to determine. Im surprised you got someone at Remington to even answer your phone call.

Maybe they repurposed some employees from the ammo division since they're a bit light on work.

Since you bought it used, is there any chance the original owner might have installed a reduced power hammer spring? I tried one in my 1895 Marlin and I got light primer strikes so I put the original back in. Problem solved.

That thought occurred to me too. A buildup of grot inside the breechblock, impeding the firing pin, would be another possibility, as would a worn/damaged firing pin.

Were there any other symptoms of excessive headspace? Primers backed out after firing, for example? It may be that your gunsmith managed to shut the action on a no-go gauge, but did he use any force at all? The test is that the rifle closes with no resistance.

Check all of the screws to make certain that they are tight.

The action is a number of pieces, and if the screw in front of the lever is not tight things stretch out giving you misfires. On my rifle I use a bit of blue Loctite on that particular screw. If I don't after about 20 stiff rounds down the pipe I get a loose screw. Check all of your screws!

It also would not be unusual for some idiot to have lightened the hammer spring so that they could work the action faster. Cheapest is to c heck and make certain that the rifle is tightly assembled.

I had a similar problem with my 444 Marlin with misfires. Mine had noticeable drag on the firing pin when I pushed it forward with my finger. It turned out that the spring, that disconnects the back portion of the firing pin when it's not in battery, was catching on wear marks (or tooling marks) where it slides on the pin. I cleaned up the roughness on the firing pin and it solved the problem. If it ever gives me trouble again I'm going to a 1 piece firing pin.


Lee

I had a 35 Remington that would do that. I replaced the firing pin and all springs that I could and it did not solve it . Down the road it went

Some good ideas, thanks. I will see what Marlin says once they have looked it over.

also if your model is a cross bolt safety, that can sometimes become partially engaged if it has wear/weak spring.

I had the same problem with my 1895SBL. It was a combination of two things that caused my occasional misfires.
1. A lightened hammer spring, along with
2. CCI LR primers

The lighter spring worked fine with Federal 210M primers but after a switch to the CCIs the problem began. I put the original hammer spring back in the rifle and started to load with Federal primers again.

Problem solved!
I thing either change would have resolved the problem but it was easy enough to do both.

I have found it is important to keep it very clean.If I keep it maintained I have no issues

My son's 45/70 guide gun misfires with CCI 250's. Switch to Federal,problem solved.