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Discussion Starter #1
Gents:

Got a problem with a 4 yr old new vaquero (45 colt): been getting misfires. Looks like it could be light primer hits. I don't know how much of the firing pin should be protruding when the hammer is down, but this gun looks like it has just slightly over the length equivalent of the pin diameter. Been using starline brass and various brands of primer and unique. Seems like the problem gets worse after 50-100 rounds are fired without cleaning.

Any thoughts?

Northwoods (of MN)
 

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Northwoods; First check the firing pin travel. Cock the gun, hold the hammer, and pull the trigger while letting the hammer down to push the firing pin as far forward as possible. While holding it in that postion get a measurement on how far the firing pin protrusion is......should be about .055 to .065. If it is not, check the nose of the pin for damage,. If the pin is not damaged in any way, clean the pin, tunnel and orfice. Take another measurement to see if that helped. If it does not, check the sides of the hammer, and the mating areas of the reciever for any obstruction that may be limiting the hammers ability to strike the pin to its full travel. If need be you might have to "clean up" those ares to alloow for proper function. Also check to insure that the transfer bar safety is clean, free and operating properly. There can be other issues involved, but these are the simplest first steps to follow.
 

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Good suggestions from Flat Top. Another approach is are the primers fully seated in their pockets? Since the problem doesn't show up right away, are the cartridges fully chambering once the chambers start collecting residue? It's possible that some of the firing pin force is used up if either the primer or cartridge can be moved forward when the firing pin strikes resulting in light strikes.
 

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northwoods; One more thing, which is actually step 2:......check to insure that the top step of the hammer fully engages the firing pin, and that in part, the transfer bar safety is not blocking full engagement of the hammer with the firing pin in any way.
 

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Usually when the transfer bar breaks they don't fire at all. It happens rarely.
 

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It'll be a cleaning, seating, or perhaps even a chamber throat issue. The last is an extension of what Marshal suggested. It is generally good to get bullets up to about the throat diameter, but if the full diameter of the bearing surface of the bullet sticks out of the case far enough, it can drag in the snug throat and cause Marshal's failure to chamber fully and firmly. It gets worse as fouling accumulates.

You probably should slug the chamber throats and bore to make sure the chambers are very close to the same size and are all bigger than the bore grooves by 0.001" to 0.002". If not, you can pull the cylinder and send it to these guys, and they will ream them to 0.4525", or you can buy or rent a reamer and do it yourself, if you are so inclined. I've seen several Ruger revolvers with undersize chambers and throats, and I gather the Vaqueros are no exception.
 

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Discussion Starter #7
thanks for the tips, guys. I have measured the chambers, and polished them up to the proper size. Got a feeling its crud buildup. Unique does not burn all that clean, but is a good powder otherwise. Faster powder leads the bore. I did have the problem of brass sliding back and sticking before (I wasn't full length sizing) and fixed that by -well - full length sizing! I checked the pin exposure and it looks about right. THe throats were pretty cruddy so cyl got soaked in #9 over night. I plan to run out a batch of new loads in the next week, and will make sure all is as it should be- clean gun, brass, clean primer pockets,etc. Heard one suggestion off the web- something about a turned hammer spring hitting the trigger spring. Can't quite figure this one out as hammer spring can't rotate hardly at all.

Back to the loading bench...

northwoods
 

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Not full length sizing is a big problem, because the case will not headspace fully and the energy of the firing pin is expended by pushing the case in the chamber. Remember that the .45 Colt and other rimmed cartridges headspace on the rim and need a clean and full contact area or things like misfires will happen.
 

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On my Rugers the hammer rests on the frame and never touches the firing pin. When I cock the hammer and pull the trigger the transfer bar moves up to fill the space between the hammer & firing pin. If someone (like me) tries to do a trigger job and polishes the full cock notch in the hammer a little too much, the hammer can fall before the transfer bar is fully in the "fire" position. When that happens I get a light primer strike and a misifre.
Or not, .... just sayin'
..
 

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. . . Remember that the .45 Colt and other rimmed cartridges headspace on the rim and need a clean and full contact area or things like misfires will happen.
When I chamber a round in any revolver, I expect to hear the round make a slight "thonk" noise as the rim contacts the chamber. When that doesn't happen, I know something is wrong be it a chamber full of powder residue or a round that is out of specs. Usually it's something simple like residue in the throat preventing the round from fully chambering. A thorough brushing of all chambers periodically is not such a bad idea during a firing session.
 
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