I bought a beat 20ga here on CGN's to use as a truck gun.Today it misfired with Rio factory ammo twice on Huns costing me birds.My handloads and Imperial factory shot fine.Does the Rio stuff have hard primers or should I replace the firing pin and hammer spring?For all I know the gun may have been stored cocked for decades? The Cooeys don't have a firing pin spring do they? Not sure what protrusion is correct?
Cooey 840 light hammer strikes
- Thread starter mbogo3
- Start date
Often the 'rocker' on the end of the hammer spring that causes the hammer to rock back after firing can be the problem. This 'rocker' is at the end of a strut that fits inside the spring. Some times it requires alteration.
Some times the combination of a short firing pin and a weak spring is the problem.
If you don't want a smith to fix it buy a new hammer spring assembly and try that...
Some times the combination of a short firing pin and a weak spring is the problem.
If you don't want a smith to fix it buy a new hammer spring assembly and try that...
I'll get some assistance taking it apart Tuesday and see what's inside.The firing pin flops around in the hole like there's room for a wool sock as well ,though the hammer spring still seems strong.It is the curved down model hammer so that I would also change.The firing pin appears to be bent down somewhat but lockup is tight.The only light primer strikes were with Rio shells and about a 1/2 dozen 3" paper Gevolot shells that have huge copper primers it would fire but the pin barely made an impression? Might be gunk and a bent pin?
I believe it is best to remove the hammer spring assy first... look at the rear piece on the strut... is there a small hole in it... there should be a corresponding hole in the strut... and when they line up you can insert a small nail through and that will capture the spring within the assembly... you don't need to remove the hammer...
I did but thanks,a finishing nail through the hole while cocking the hammer until it lines up and out it popped.I taped the two springs under the opening latch so they wouldn't go airborn while tapping out the hammer pin. Guerrilla gunsmithing I figured a brass door hinge pin would be about the correct size and it was.McGiver would be proud.Got the pin and hammer out and replaced with the better angled new one.De-greased the lot with brake cleaner.Now I can use some advice on where and what to lube before putting the stock back on.What type of lubricant etc ?It appears the rocker,plunger and strut are in good shape so they didn't get replaced.We'll see when I test fire it with the previously difficult Rio factory ammo.
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Often the 'rocker' on the end of the hammer spring that causes the hammer to rock back after firing can be the problem. This 'rocker' is at the end of a strut that fits inside the spring. Some times it requires alteration. Too much on the 'rock back' not enough on the 'push forward'.
Hold the hammer ahead as far as possible... how much does the firing pin stick out?
You can always buy some good ammo and test it too.
I get .056 protrusion of the firing pin? Doesn't sound like much? I don't think I can find a new rocker so perhaps someone that knows what they are doing can build this one up? I may take a new minty assembly from another gun and swap out the part as a test and see if it goes bang.I put the brake cleaner to the ejector crevasse and a lot of black !@#$% came out. Works fine with Imperial factory fodder or my Win AA handloads but I want it working with everything.
Been following this with some interest. I had somewhat the same problem ,and finally noticed that the rims of some brands of shells (offshore particularly)seem to be thinner. My theory is that this allowed the shell to sit a tiny bit deeper in the chamber, perhaps just enough to escape the full force of the firing pin blow. I "solved" the issue by simply feeding it what it liked. Not a fix, but avoided a lot of grief.
I get .082 protrusion with the pin nudged all the way forward.Which sounds better. I think you may be on to something adding to the back of the pin. How does one do this without taking the temper out of the steel ? Or should I just grind a piece of drill rod or sacrifice a bit?
The Rios appear to fit flush. Rim thickness is another story Rio .049". Gevolot .062 " Imperial .059" And Win AA .066". I took a bolt ,drill as I don't have a lathe ,files and a Dremel and in 2.5 hrs made a firing pin slightly longer than the original.Heat treated both ends to cherry red then quelched in vegetable oil to harden .See what it does tomorrow.
