occasional light strikes

[Virgil Ray Hality]

So, the gun is a Uberti Open Top chambered in 44 Colt.  I get an occaisional light strike.  Most times, the primer will ignight on the second strike.  About 1/3 of the time it will not.  I checked and did a lot of different things to this firearm,which, at one time would pierce primers and light strike em with the same cylinder fulll.  I think I have most of the issues fixed, except I get 1 out of about 100 that still strike light.

I read that SAMII specs say that primer pockets for large pistol primers should be between 0.118 and 0.122 deep.  I am not sure how deel the top of a properly seated primer should be.  I started to seperate out the shell from ammo that had light primer strikes.  What I found is that the shells that did not fire, or did not fire on the first strike all had primer pockets that are 0.115 which is shallower than SAMII specs. Before I cut bak the rear of the cylinder to adjust head space, I wanted to ask a few of questions:

  1)  What should the head space be on my Open Top?   
  2)  Can a shallow primer pocket be causing the anvil and cup not to seat properly, or squish the priming compound out of the way?
  3)  What should the depth of a poperly seated primer be?

Any help would be great.  Thanks.

[Fox Creek Kid]

Cut back the cylinder to adjust headspace? HUH?  Headspace for these is regulated by the fit of the gas ring at the breech face. Only a pro should even attempt this as your pistols will be FUBAR in short order. When you adjust anything on a Colt style wedge frame EVERYTHING else must move in relation to that. Sometimes the rim thickness on brass cases vary tremendously hence the variation in the distance from the primer to the frring pin. There's an easier fix. By some new firing pins and have them fitted professionally. Luckily for me my gunsmith runs a public range and we did it a few licks at a time and then a test fire until we got a good solid strike just this side of piercing.

[Virgil Ray Hality]

Kid, 

Been to "professional" smiths twice.  W/ costs totaling almost as much as the gun.  I think the gunsmith option will not help round these parts.  Besides, the hammer and pin assembly have been replaced with a new hammer (w/new model firing pin) and hammer screw. 

Your point about the rim thickness on brass cases varying tremendously is good to note, and a new thing for me to look at.  I will check that out.  Thank you very much for that info.

[Virgil Ray Hality]

Well, I think the new firing pin was too short.  I also now know I have a real fead space probem on this revolver.  It looks like the replacement pin will be long enough to do the job. 

[Be-A-triss Bandit]

Glad you got 'em working.
My Cimmaron 1872s appeared to have excessive head space and they pierced primers with the original firing pins.
For problem #1) Trimming 44 Special brass to 44 Colt length is perfect.  I think Uberti built them all for 44 Special/45 Colt cases rim thinkness.
For problem #2) Install aftermarket firing pins which are less pointy and stronger. www.thesmithshop.com
Two questions though:
Why would increasing headspace fix misfires?  Should do just the opposite.
Why would shallow primer pockets cause misfires?  Shallow seated primers not touching the bottom of the primer pockets cause misfires.  Shallow pockets cause high primers which can cause cylinder jams but 
Try the trimmed 44 special cases.  They fit perfectly.
BB

[Coffinmaker]

Virgil,

The Open Top is sensitive to head space.  Optimum head space should be 5 thou, +/- .001.  Often there is a "run-out" problem with Open Top cylinders.  Front and Rear faces aren't machined parallel and out of concentric.  Usually not enough that it can't be delt with.
You will need an automotive type flat feeler gauge set.  Load the cylinder with resize unprimed brass and check head space at each chamber before you do any refining of the head space/end shake.  As posted above, when you "adjust" the head space, you may well have to "adjust" all the other clearances as well.  In some instances, I have had to completely replace a customers cylinder and re-fit it.
If, your gun is experiencing this much light primer strike misfire, first CALL CIMARRON.  Give them the opportunity to make it right.

Coffinmaker 

[Sir Charles deMouton-Black]

See Hellgates post today on SCORRS on a similar topic.  How far the wedge is driven in affects headspace directly on open top colt style revolvers

[Montana Slim]

Primers will make a difference, too. If you're using CCI, might want to try another brand.

Slim