GP100 question?

R

rrruger

New member
I have had some mis fires using factory ammo in my GP100. I have gone to a lighter main spring and then back to stock, and in both cases the misfires seem intermittent.
I now wonder if the misfires are not so much a result of spring weight as play in the transfer bar? I notice that the transfer bar can move around a bit and this 'play' must absorb some energy from the falling hammer. I also wonder if burned powder between the transfer bar and the frame might cushion the firing pin strike enough to cause a light strike?
I would like to ask those of you that have transfer bar revolvers to comment.
Am I just blowing smoke, or does my thinking make sense?

By the way, the mis fire rate is about 1.5% and those mis fires do go BANG! on the second attempt. Either way, this is 1.5% too many failures for me.

I look forward to your input.
 
Are you shooting reloads or factory ammo? I had some issues with some reloads of mine that didn't have the primer seated all the way in conjunction with also running a 9lb hammer spring.

Once I switched to a hand priming device that fully seated the primers and bumped up to a 10 lb spring I haven't had any issues.

Transfer bars have some play, and I don't think that or un-burned powder would be the culprit.
 
The transfer bar is supposed to be very loosely attached and there is normally a lot of play. I have a couple of GP100s and another Ruger revolver (Super Redhawk) with the same basic mechanism. The transfer bars on all three are very loose and none of the revolvers has ever misfired.

Here's a relatively simple check you can do to see if the mechanism is working properly.

Unload the revolver and leave the cylinder open. Hold the revolver in your right hand in a firing grip.

Pull the cylinder latch forward with your left hand--it will pivot forward. Hold it in that position.

With the cylinder latch held forward, pull the trigger and HOLD it.* Do not release it. With the trigger held back, you can release the cylinder latch and look at the breechface. You should be able to see the firing pin protruding from the breechface. If you have the means to do so, you can measure the firing pin protrusion. It should be sticking out of the breechface about 0.05".

Pivot the cylinder latch forward again, and pull the trigger and hold it again. While holding the trigger, check to see that the firing pin is protruding the proper amount. Try this several times to insure that the firing pin protrudes each time the trigger is cycled and held back.

If the firing pin is protruding each time you cycle the trigger and is protruding about the proper amount, then the problem isn't in the hammer/trigger/transfer bar mechanism. It could be a spring that's too light, or it might have something to do with the cylinder/headspacing, or perhaps the ammunition.

*Although it is possible, using this method, to cock the hammer and then close the cylinder, this should NEVER be done with a loaded cylinder. It could potentially cause the hammer to fall unexpectedly, and if the trigger is being held to the rear, the gun could fire--possibly without the chamber properly aligned with the barrel.
 
I've been having a few failures to fire with my GP100 as well. All handloads in my case. Only has happened with Tula primers though.
 
Sounds like the Tula primers are either harder to ignite, or they are slightly dimensionally different from standard primers and, as a result, aren't being seated exactly right.
 
The transfer bar is supposed to be very loosely attached and there is normally a lot of play. I have a couple of GP100s and another Ruger revolver (Super Redhawk) with the same basic mechanism. The transfer bars on all three are very loose and none of the revolvers has ever misfired.
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+1.

I'd guess your gun is fine and reloads are the culprit.
 
I have had the same issue using Wolf primers in various guns. Wolf and Tula are both Russian, not sure if they come out of the same factory, but that's a possibility.

I've noticed that on the misfires that I have with the Wolf primers, they are seated in further than they should be, and therefore have a very light firing pin strike. So it is a dimensional issue. I haven't taken one apart to measure, but I am suspecting that the misfired primers won't be as tall as they are supposed to be.
 
Sounds like the Tula primers are either harder to ignite, or they are slightly dimensionally different from standard primers and, as a result, aren't being seated exactly right.
Click to expand...
Yeah, still trying to figure out exactly what the problem is.

I've noticed that on the misfires that I have with the Wolf primers, they are seated in further than they should be, and therefore have a very light firing pin strike.
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Generally, primers that are not seated deep enough cause light strikes. The high primer cushions the firing pin's blow, moving in as it is hit.
Primers should be .003" - .005" below the case head, bottoming out in the primer pocket.
 
I have also had the same problem with my gp-100. I am eventually going to send it back to Ruger. Mine is doing the same with factory or handloads. Maybe 1 in a hundred. I researched it a while back, and best I could come up with is a firing pin protusion issue. I figure if I send it back now I'll have to wait months to get it back so I'll wait to this frenzy is over. (I hope they'll ay the shipping !)
 
Under_Dawg, I just got done dealing with Ruger's CS last month (March 2013), turnaround time for a replacement gun was three weeks from the day of the call. Turnaround for repair was two weeks.

Your results may vary, but in my experience Ruger is still on the ball with their service in these high-pressure times!

Ivan
 
Your results may vary, but in my experience Ruger is still on the ball with their service in these high-pressure times!
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Good to know.
I researched it a while back, and best I could come up with is a firing pin protusion issue.
Click to expand...
I thought that as well, but mine seems to have plenty protrusion, traveling more than halfway between the recoil shield and the cylinder face.
Mine does seem to have a very stiff firing pin spring that has to be overcome by the mainspring. I also see a lot of drag marks on the side of the hammer, so I'm going to try the shim set from triggershims.com and slick up the action while I've got it apart.

I also wonder if there's some issue with the transfer bar. Maybe bent or some other issue where the transfer bar is taking up more than it's fair share of the hammer blow.
 
Hammerhead said:
I thought that as well, but mine seems to have plenty protrusion, traveling more than halfway between the recoil shield and the cylinder face.
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When I measure my GP100, there is a gap of about 0.014" * between the cylinder face and the firing pin.

The gap between the recoil shield and the cylinder face is about 0.064" on my gun, so that means the pin should protrude between 75% and 80% of the way to the cylinder face.

If your gun has a firing pin protrusion on the low end of the spectrum and the Wolf/Tula primers seat deeper than U.S. primers (requiring more firing pin protrusion than normal) as suggested by Gdawgs, the two issues may be combining to cause a problem.

In addition, if, as Gdawg suggests, the primers should be seated more deeply than one might expect and you are seating them to normal depth, then they wouldn't be seated properly. As you correctly note in an earlier post, not seating primers fully is a common cause of misfires.
I also wonder if there's some issue with the transfer bar. Maybe bent or some other issue where the transfer bar is taking up more than it's fair share of the hammer blow.
Click to expand...
I have heard of broken transfer bars, but never of a bent transfer bar. I guess it could happen, but I don't think that would be something I would suspect.

In any case, the transfer bar can be easily removed. Strip the gun as detailed in the manual. Take the trigger group and carefully squeeze the trigger and the tranfer bar will probably fall out. Be sure to look at the trigger group carefully to see where it's supposed to fit before doing this.

You can take it out and post a few pictures (front, back, side views) and it should be readily apparent if it's bent or otherwise sufficiently abnormal to cause a problem.

Ok, all that aside--since you note that you are only having issues with one type of primer (a brand known for having dimensional issues--and I'm not speaking only about Gdawg's comments), it doesn't really make sense to focus on the gun in your trouble-shooting process.

* When measuring this, be careful not to compress the firing pin spring with the feeler gauge leaf. If you feel the feeler gauge "snap" out from under the firing pin, the spring was compressed and you need to try a thinner leaf to get an accurate reading.
 
I have a GP100 (it is my workhorse), as far as I know the transfer bar is supposed to have a little play. I have fired both factory and hand loaded ammo thru it with no misfires.
 
Good stuff JohnKSa, thank you.
I just measured the protrusion with the method in post #3. I get an average of .048".
I was also seating some Federal SPP's just now in the Win brass I'm using. Using a Wilson cartridge gauge and a dial indicator and the rims are all over the place, from -.004" to + .008" relative to the top surface of the gauge. Primer depths vary widely when done by feel on top of the press with an RCBS Ram prime. From -.008" to -.002".
Gotta' run, not much shooting light left.
Thanks for all the help.
 
I just measured the protrusion with the method in post #3. I get an average of .048".
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That should be good, as long as the cylinder/breechface gap isn't larger than normal.

In retrospect, the distance between the firing pin tip and the cylinder face is probably more significant to the issue at hand.
 
I would agree. If you have limited protrusion, large headspace, a thin rimmed case with a deep pocket, the errors might add up against you.

FWIW, just shot a bunch of Federal SPP primed Winchester brass, no troubles even though some of the primers were .008" below flush. (seated by feel, then checked with a dial indicator)

I had been seating my .357 primers to a predetermined depth (-.003") instead of by feel. Maybe my misfire was deep primer pocket.

My next test will be to see of Tula primers seated by feel will go off 100%.
 
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