View Full Version : Need some revolver advice

02-09-2012, 12:02 PM
I've got a new-to-me Ruger GP100 with a cylinder that occasionally binds up. As far as I can tell (thank you IBOK) the headspace is a little short. With a cartridge in the cylinder, I measured it as .006" - .007" while the in-spec range is supposedly .008" - .012" with .010" being ideal.

What should I do about this?

I called Ruger customer support and they weren't very helpful. They were not able to tell me what the headspace spec should be or the best way to measure it. They did say I could ship the gun if I wanted to but made no guarantees that anything would be done with it or that any work done would necessarily be covered by warranty.

I considered trying to do the work myself, but the importance of a thousandth of an inch has me a little hesitant.

I would be willing to have a gun smith look at it. Can anyone recommend a good smith in the vicinity of Berkeley? If it would be reasonably cheap, I'd be totally happy with this route.

If the headspace will loosen up with use, that would be ok too. I just can't have an unreliable weapon.

Any advice?

02-09-2012, 12:28 PM
Other factors might be causing it to bind.
High Primers, dirt under the star extractor, barrel to cylinder gap, etc.

How much front to back play is there in the cylinder?

Does it only happen after you shoot a bunch, or can it happen with the first six rounds? Have you tried it with various ammo with the same results?
Are you shooting on the low end or the high end of the spectrum when this occurs?

Too little information to really know what is happening.

02-09-2012, 1:00 PM
The SAAMI spec for headspace on 38/357 revolver is 0.060" to 0.074". This is measured from the back of the cylinder to the breechface. I know S&W recommends the headspace be 0.060" to 0.066". I think Ruger is the same. Before you measure it, check that the firing pin hole is not peened. Sometimes a lip of metal builds up there and will bind the cartridges giving an illusion of a headspace problem.

02-09-2012, 1:07 PM
Clean really well under the extractor star. My SP101 was binding up, it looked clean under the star but I gave it a little more and the problem went away.

The headspace should not bind anything up unless there is foulant built up on the cylinder face and forcing cone. Also check that there is nothing in the firing pin hole.

Are you shooting reloads or factory rounds? Are the primers flush or protruding?

02-09-2012, 3:08 PM
Thanks for the replies so far. Some additional information.

This has only happened to me a few times so I don't have a lot of data. So far it's about 1/100 rounds. They've all been with .357, never with .38 spl, all were factory with flush primers. Measuring the head on the rounds, the .357 were .001" thicker than the .38 spl (.054" vs .053") which puts the overall headspace at ~.060" - .061". It sounds like that's at the low end of the range but still acceptable.

I did make sure the cylinder was clean after the first time it happened and it still popped up (eventually). I guess it's possible that the extractor star on the cylinder is just getting crap blown under it. I have checked the firing pin hole and it's smooth. The b/c gap is small too, though I don't remember exactly what I measured it as. The front-back play on the cylinder is negligible (~.001").

02-09-2012, 4:00 PM
Are you firing .357s after .38s? If so, the powder is probably building up at the seat of the cylinder. Unburnt powder collects there causing the longer .357s to not seat fully. Is this what might be happening?