Primer not going off

[wvmtnman]

Let me start off by saying I am new to Spencer's and reloading. 
   I have an 1860, 56-56.  I went out today and could only get 8 of the 20 to fire.  Many took 2 hammer falls to go off.
    The conversion block I have, has 2 screws in the plate.  On a closer look, i noticed that the back screw was brock off in the firing pin base.
   Front screw is fine. It looks like the front screw may adjust the depth of the firing pin.  I did these but still didn't have any luck.
    And help would be appreciated.
           Thanks, Brian

[El Supremo]

Thanks, Brian/"wvmtnman":

We've been texting for a while and I see your upper block photo's in your text tonight. Please try to add here. I have never seen that style, but it looks good.

The striker has a small coil spring behind the firing pin, so yours is an "inertia" style that should retract the pin tip to prevent dragging on the primer as block lowered without hammer at half cock.

Normal SAAMI rifle firing pin protrusion ranges .035" to .050". Please push your striker full forward and measure pin tip protrusion. If ample, then FTF's are probably weak mainspring, gap betweem block face and primer or tough primer cup metal.  Winchester large rifle primers seem the easiest to ignite.  I have lots of second hits needed  with CCI's.

You can add layers of clear tape to rear of case to feel block gap/resistance. If more than one layer produces no felt resistance,  maybe case rim narrow or rim cut excessive.  Rim and cut should be around .065".

Please add photos of the Spencer.  Thanks.
El Supremo/Kevin Tinny

[wvmtnman]

Pictures added

[Arizona Trooper]

That looks like a shop special centerfire block. Nicely made, but the screw that connects the slide to the firing pin carrier takes all the force of the hammer, and it's loaded in shear across the threads. Screw threads loaded in shear are a recipe for failure, which is what yours did. When that screw failed the carrier was no longer firmly connected to the slide, so you got misfires. Depending on exactly how the parts are made there are a couple possible ways to fix it.  Unfortunately, the better ways all involve a trip to a machine shop. You could just replace the broken screw and it would work for a while, but the screw would eventually break again, and it's probably a custom made screw. The easiest way to solve the problem (and it's probably not too easy) is to add a shear pin connecting the slide to the carrier, between the two screws. That way the unthreaded pin takes the hammer strikes instead of the screw threads. Bigger is better for that pin, If it's too small diameter it will eventually pound loose and your problem will come back.

[DJ]

I haven't seen it in action, so don't know for sure, but the firing pin carrier (part where the hammer strikes) looks kind of short, at least compared with an original rimfire firing pin and the other centerfire conversions I have seen.  Perhaps your firing pin carrier is not getting a good solid hit from the hammer.