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GP100 barrel shank size

Discussion in 'Gunsmithing and Repairs' started by xtratoy, Oct 8, 2013.

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  1. xtratoy

    xtratoy Member

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    Can anyone supply me with the size of the threaded shank and thread per inch of a Ruger GP100 barrel ? I was wondering if any other gun barrel could be used in a GP100 frame. It appears that S&W barrels show up more often as parts for sale. Maybe a Taurus Barrel could be modified. Thanks for any help with this question.
     
  2. BBBBill

    BBBBill Member

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    Why would you want to put some other manufacturer's barrel on your GP100? If yours is damaged, why not stick with a Ruger replacement? GP100 barrels do show up for sale on GunBroker and AuctionArms. Don't know about GP 100 thread pitch, but the older SIX series barrels were different from S&W and Colt. Ruger supposedly uses some kind of thread locker on their revolver barrels which has resulted in some destroyed frames when folks tried to pull the barrels, even when using the proper receiver wrench. Do you have a receiver wrench?
     
  3. xtratoy

    xtratoy Member

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    I am totally capable of making a form fitting receiver wrench. As to why put a different barrel on, Why not if it would work. Have you never heard of a Smolt or Smython? A lot of custom guns use barrel from other makers. Rugers end up with S&W barrels frequently from custom gunsmiths. Another favorite barrel people like to use is the Colt Anaconda or Python barrels. While I am able to unscrew a barrel from a frame, I do admit that I will have to utilize the services of a capable machinist to clock the barrel properly to the frame. I wish there was a pile of GP100 barrels just waiting to be had, but that doesn't appear to be the case. The use of any barrel for me is predicated on the barrel having the proper sized shank and thread size. I still have not received any information as to the thread size Ruger uses on the GP100. I have a Kunhhausen book for the Ruger single actions but that does me no good for this gun.
     
  4. BBBBill

    BBBBill Member

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    No inferences as to your capabilities. Just straight up questions about where you were going and why to help guide the answer. Yes, I have heard of Smolts, Smythons, and Cougars. They all started with longer barrels shortened on the breach end and rethreaded to fit. Actually, I owned a Cougar many years ago. It was stolen in the late 70s.

    http://www.gunbroker.com/Pistol-Parts/BI.aspx?Keywords=GP+100 No barrels currently listed, but I do see them there fairly often.

    The previous caution about the adhesive is specific to the GP 100s. The earlier Rugers were not "glued" in. Hamilton Bowen is a master revolver smith with a lot of experience doing this. You might contact him for advice on barrel removal specific to the GP series. Could save you some trouble/ruined parts.
     
  5. BBBBill

    BBBBill Member

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  6. xtratoy

    xtratoy Member

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    BBBBill, I appreciate your help on this. I have just enough ambition and tools to either get the job done or create a bigger problem than I started out with. I have that barrel on my gunbroker watch list and hope that the price doesn't spiral out of control. I thought about just sending the gun to one of the premier gunsmiths and having it converted to a 10mm, but remembered that I don't have that kind of cash laying around. At the worst this will be a backburner project until I can acquire the parts needed to complete it .
     
  7. Jim Watson

    Jim Watson Member

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    Revolver barrel threads from Brownells list of taps and dies:
    GP 100 .625x24
    Colt SAA .695x20
    S&W K .540x36
    S&W L .562x36
    S&W N .670x36
    Ruger SA .680x24
    Redhawk .750-20
    Colt Python etc .563x32
    Colt Python .562x36 post 1991.

    Sorry, I could not find the shank thread specs for the Anaconda. Chances are not good that it would match the GP since it was made in .44 and .45 and is probably as large as if not larger than a S&W N or Blackhawk.
     
  8. xtratoy

    xtratoy Member

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    Jim, that list shows that depending on the minor thread diameter of a S&W Model 28 barrel, it could be a possible donor barrel since it has an enclosed ejector rod like the GP100. If it could be turned down and rethreaded with the correct thread for the GP100, that looks like the only one that may work. It would be a two tone gun as I don't think the Model 28 was ever offered in Stainless. I did see some of those barrels while searching. The Model 28 Highway Patrolman is 357 Magnum caliber. Thanks for finding that list of barrel thread diameter/TPI. I am heading to Brownells to try and find the list of taps you posted. Thanks for the info!!!
     
  9. xtratoy

    xtratoy Member

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    Jim, I tried finding those taps but ended up chasing my tail in circles. I always have a hard time chasing down special tools on their site. Can you tell me how you got to the specific taps you listed? Special keywords I may be missing? I clicked on the gunsmith tools tab, then on handgun tool / taps and dies and still didn't find them.:confused:
     
  10. Jim Watson

    Jim Watson Member

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    I cheat, I have the print catalogue.

    I got the Colt diameters off a gunboard that Bing turned up. Nobody cared what an Anaconda barrel measured. The gun prices are so escalated, nobody is working on them anyhow.

    There are Smolt/Smython conversions out there with a .562x32 Colt barrel taken down to K frame .540x36. I am told that there is some amount of old thread showing and the shop just kind of cross threads over it. If so, it won't be pretty and you might not be able to get it back apart, but they shoot.

    I have seen Smythons on N frames. Looks like you would have to make a bushing for that.

    Apparently a late model (one front sight pin) Python barrel should go right into a L Smith.
     
  11. xtratoy

    xtratoy Member

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    I got the parts kit off of gunbroker. I will upload some pics of my progress so far. The new replacement barrel went just past where I needed it to be so it looks like I have harder route than the easier one. I will have to remove approximately .035" to get the barrel where I need it prior to final tightening.

    Frame and barrel blocks. I roughed out wood blocks and then took up the gap with JB Weld epoxy for an exact block to frame fit.
    20131106_182946.jpg
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    Gun clamped in blocks with barrel block taped on.
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    Barrel off
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    Where the original barrel tightened down prior to final torquing.
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    Where barrel I bought tightens up.
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    I was hoping that it would have been before rather than just past where it needed to go. Trying to decide whether to face off the mating surface on a lathe or use an aggressive grinding compound and spin the mating surface down the approximately .032" it needs to go to end up like the original barrel is.
     
    Last edited: Nov 6, 2013
  12. xtratoy

    xtratoy Member

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    Poor boy machining. I am using hardened steel drive wheels from a Lincoln Mig welder. These are large enough to cover the barrel lug area and the frame area. They have parallel surfaces front to rear unlike a common washer. Another good thing is the shaft hole is .625 / 5/8", the same as the threaded barrel shank. I got some self adhesive sandpaper and stick it to the drive wheel and sandwich the drive wheel between barrel and frame and rotate the wheel while applying pressure to the barrel by tightening as I turn the wheel. right now I am almost half way to where I need the barrel to be for final torque. Then I will have to order the forcing cone end facing cutter from Brownells to set the cylinder gap.
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  13. xtratoy

    xtratoy Member

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    I needed to clean up where the threaded shank met main body of the barrel. My other method was working slowly but it looked like I was loosing the tighter radius needed for clearance. I dug out my 4 jaw chuck and put it on my little Craftsman/Atlas lathe. There was no way to hold the barrel with a 3 jaw chuck. I will go back to my previous process after I clean the area described above. I don't trust facing off the whole barrel surface because it would suck if the bit grabbed and messed up the barrel. The lower lug around the ejector slot holds much potential as an area the bit could grab. I have had projects 1% from being finished and had that happen before. Not fun!
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    Last edited: Nov 8, 2013
  14. BBBBill

    BBBBill Member

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    The rear face of the lower lug would normally be clearanced so that only the rear face of the barrel around the threaded shank bears on the receiver. Doesn't take much. 5 thousandths is plenty.
     
  15. xtratoy

    xtratoy Member

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    Thanks for that info. I have never done this before so everything helps. I have built some FAL's from parts kits and new upper receivers before. The main thing on those is getting the barrel clocked correctly for the final torque down. The inch model use a round shim/washer that has to be thinned down to set the clocking and metric ones have to be filed down on the barrel shoulder to clock before final torquing.
     
  16. BBBBill

    BBBBill Member

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    Yep. Built a few FALs, too. Your first barrel fitting method reminded me somewhat of a popular "redneck" barrel shoulder fitting method often used on them. I've atually shimmed a couple metric barrels that turned in a little too far. Cut shims out of stainless shim stock.
    That 4 jaw chuck works better for precision turning than a three jaw ever will.
     
  17. xtratoy

    xtratoy Member

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    I finished my barrel swap finally. I was moved to swing shift and working 6 days a week since the last post on this. Here are a couple pictures of the barrel before torquing it down. I took the measurements off theold barrel to figure cylinder gap. I then turned on the lathe since I didn't want to spend the $55 dollars + shipping costs to buy a facing tool once the barrel was installed. I ended up with a .003 cylinder gap. Here are a couple pics just before torquing it down. 20140831_150646_resized.jpg

    20140831_150623_resized.jpg
     
  18. BBBBill

    BBBBill Member

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    Glad you got it done successfully. I guess I never understood why you embarked on this project. Bulged barrel? Poor accuracy? Wanting a shorter/longer length? You may find that the cylinder to barrel gap is a little tight. You might be able to rent the barrel facing and forcing cone cutters if you find that you need to adjust. Nice hack on the frame wrench.
     
  19. xtratoy

    xtratoy Member

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    It had a slight bulge in the barrel (squib load from previous owner?) in the section just forward of the frame. I looked it over as well as I could where I bought it and didn't figure it out until I ran a Lewis Lead remover down the bore and felt the loose spot. The out side of the barrel just ahead of the frame for about 3/4" measures .008" larger measuring on the round part of barrel. The lug section on the bottom and the upper rib section show no difference in measurement. It shot fine but that bulged barrel irritated me. I sent it back to Ruger but they wanted just shy of $400 to fix.That was more than I was willing to shell out on top of what I already paid for the gun. I also wasn't willing to pawn it off onto the next guy.
     
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