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Thread: Difference in cylinder diameter between Ruger GP100 6 shot vs 7 shot

  1. #1

    Difference in cylinder diameter between Ruger GP100 6 shot vs 7 shot

    I have been looking at the GP100 and comparing it to SW 686. There are several things I like about the GP100; No side plate, Simpler takedown, easy front sight replacement and 3 point cylinder support for alignment. I owned a 1986 SW 686 for 34 years and had no issues. It is a great pistol. But I never looked at a Ruger equivalent. The 7 shot cylinders were not a thing in 1986. Just wondering if the larger diameter has downsides . If I was not using for concealed carry cylinder size seems like a non-issue. Would appreciate thoughts on 6 shot vs 7. Having an extra shot seems like a good thing. But if you ever needed to defend your home or truck (purpose for this pistol) seems unlikely you would shoot that much? I have thwarted 1 attempted robbery in my life while using my truck on a hunting trip. Merely brandishing the SW 686 caused the thieves (2) to leave quickly. So is the 7 shot preferable to 6?

  2. #2
    Revolvers Revolvers 1911s Stephanie B's Avatar
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    https://pistol-forum.com/showthread....-7-shot-GP-100

    Rimlock with a 7-shot GP-100 seems to be a thing.
    If we have to march off into the next world, let us walk there on the bodies of our enemies.

  3. #3
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    I thought I read, perhaps here on p-f, that Ruger had solved that problem. As to cylinder diameter, it should remain the same. I'm pretty sure S&W kept the same diameter for their 686+ as the original L-frame. I have a 7-shot 386 and have owned a number of 6-shot 586s. I can't tell the difference if there is any. And no, I haven't measured them as it wasn't a problem.

    Someone smarter than me can correct this if it isn't the case.

    Dave

  4. #4
    Well if it is same diameter, the case rims must be closer together. Seems like a sad oversight IF any SAAMI ammo case rims touch preventing proper function.

  5. #5
    Quote Originally Posted by Rmiked View Post
    Well if it is same diameter, the case rims must be closer together. Seems like a sad oversight IF any SAAMI ammo case rims touch preventing proper function.
    I agree, but I might remember it may have been only one brand.

    Sent from my SM-G892A using Tapatalk

  6. #6
    Yes, I’m reading Blazer. I’m considering buying a GP 100. I would be inclined to get 6 shot anyway. But I would consider 7 shot IF I knew the same margin in spacing was preserved in 7 shot. There had to be a basis for the original 6 hole spacing in “6 shooters”. I guess it could Have been coincidence that 7 shots seems like it should work? As an Engineer I assumed the 7 shot cylinders were larger diameter for this very reason. And they could be larger? I have not compared them side by side or measure any. When I owned my SW 686, there was adequate space between case rims but it was a 1986 vintage 6 shot. With this potential issue, I would get the GP100 6 shot. It looks like a brute of a pistol. I watched a take-down video and front sight replacement video and it seems very easy to work on and therefore easy to properly maintain

  7. #7
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    Quote Originally Posted by Dave T View Post
    I thought I read, perhaps here on p-f, that Ruger had solved that problem. As to cylinder diameter, it should remain the same. I'm pretty sure S&W kept the same diameter for their 686+ as the original L-frame. I have a 7-shot 386 and have owned a number of 6-shot 586s. I can't tell the difference if there is any. And no, I haven't measured them as it wasn't a problem.

    Someone smarter than me can correct this if it isn't the case.

    Dave
    Cylinder diameters- The Ruger GP100 6-shot cylinder has always been 1.545" in diameter. When they first came out with their 7-shot, they kept the same size cylinder. I have one of the early examples and it measures 1.545". Crowding 7 chambers in that size cylinder meant that case rims in the upper half of the SAAMI diameter range would rim lock. The bottom half of the range work just fine. I don't own any S&W revolvers, so I don't have first hand measurements. In discussions of the problem on the Ruger DA forum at the time, others gave a diameter of 1.55" for S&W 7-shots. In December 2018, Ruger customer service began telling callers that the problem was fixed on new production guns. For the record, to my knowledge, Ruger has never publicly said what they did to fix it. Several buyers of the late version guns reported on the Ruger forum that they did not have any rim lock problems. A few supplied cylinder measurements, and I gave those from my early model. It appeared that Ruger increased the diameter to 1.55", the same as the S&W 7-shots. It also appeared that they moved the chambers outward to create more rim space. Since that time there haven't been any complaints show up on the Ruger forum, it's been a dead issue for almost a year now. Someone here on PF bought one last summer and reported back that he tried some of the most problematic ammo brands, and he didn't have any problems. And that's where things stand at the current time.

  8. #8
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    Quote Originally Posted by vtfarmer View Post
    It also appeared that they moved the chambers outward to create more rim space.
    That would require them to move the barrel upwards by the same amount they moved the chambers. S&W had to do the same with their 8 shot N frames, i.e. move the barrel to align with the increased chamber offset. While S&W openly state that they actually did move the barrel higher in the frame to align with the new chamber offset, Ruger will neither confirm or deny whether they did on the 7 shot GP. (If they did, then I missed it - my bad)

    Hence, I will not buy a 7 shot GP until I know that the barrel offset in their 7 shot revolvers are the same as the chamber offset.

  9. #9
    Agreed. If you moved chambers radially outward, machining would need to change to keep alignment with bore. I’m looking right now to purchase and if I found the 6 shot version today, I would likely buy it. I guess you could always attempt to load some Blazer in the 7 shot to observe rim-lock or not? I kinda like the 6 shot anyway. But would not be opposed to 7 if I knew the bore was moved accordingly. Ruger would need to state that or show the drawing change? I can’t imagine Ruger moving chamber out without moving bore however

  10. #10
    Quote Originally Posted by Rmiked View Post
    I would consider 7 shot IF I knew the same margin in spacing was preserved in 7 shot. There had to be a basis for the original 6 hole spacing in “6 shooters”. I guess it could Have been coincidence that 7 shots seems like it should work?
    Remember the GP is bigger than the Security Six and the N-Frame is bigger than the K-Frame, I think there was probably some wasted space in the larger six chamber guns.

    My most recent purchase was an order 686+, but I have hardly fired it so I have not formed a basis for an opinion.

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