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    • #23094
      blademasterii
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      I welded and recut the threads for my ruger mkII 3 times. Now after much cleaning and reinstalling the sights it shoots high when cold, lower when warm, dead on when hot and back to 6” high at 10 yards when cold. I tig welded the stainless bull barrel threads with stainless rod to build it back up, cut it to true and OD then threaded first with the lathe, then a die. I’m bottomed out on my sight and this was the most accurate pistol i’ve ever shot before i welded on it. Seven or eight shots out of 10 on an 8” plate at 100 yards suppressed. Recut the crown and face as well. Did I warp it or do i have a crown issue. In case you are wondering why 3 times, first time cutting threads with a lathe and got distracted the second time and wiped them, first time had to many low spots, third time fixed all mistakes and cut it true.

    • #23105
      Goodsteel
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      In my opinion, there is no more important part of the barrel than the very end. I think that by welding it, you induced stress into the barrel that is manifesting itself as it heats up.
      What I think you should do is cut 3/4″ off the barrel and start again. Leave the welder alone, as it has very little place in gunsmithing (even less than a dremel tool).
      The proper way to cut threads in a barrel is to mount the barrel in a double spider and make certain that there is not too much tension on the aluminum tipped bolts.
      You line the bore up with a range rod (PTG sells a complete line of these rods and they are inexpensive and very helpful).
      Once the bore is running true within .0005, you cut the threads with a very sharp cutter and use three wires and a micrometer to precisely gauge your pitch diameter. What you are looking for is the big side of a class II fit. Assuming you are using the .0206 wires, that would be an “over the wires” measurement of .5060.
      Next, before removing the barrel from the lathe fixture, you reinsert the range rod and check for alignment. Once you are very very sure that everything is as straight as you can make it, clean the thread seat perfectly flat, and then the barrel face at 90 degrees.
      Finally, set your compound on 45 degrees and install a sharp carbide boring bar.
      Break the leading corner of the threads about .050 by running the lathe in reverse and cutting on the back side, then throw it in forward CCW and clip the corner of the bore just enough to clean up the rifling lands and leave a slight bright ring.

      Without moving anything, screw your suppressor on the threads and put an indicator in the exit hole. if it does not run true, find the source of the trouble and correct it. You want to be able to seat the can and break it loose and have it return to an exit hole runout of less than .010 three times in a row.

    • #23128
      Alphawolf45
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      • Overall: 19

      Welding all around the muzzle has caused it to constrict with the cooling of the filler metal .Since you already have the can installed and damage is already done I would bore out the rifling for about 3/4 inch back from the muzzle , put the can back on and try it .See if that gives you back some accuracy.

    • #23134
      6bg6ga
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      Goodsteel;n1044 wrote: In my opinion, there is no more important part of the barrel than the very end. I think that by welding it, you induced stress into the barrel that is manifesting itself as it heats up.
      What I think you should do is cut 3/4″ off the barrel and start again. Leave the welder alone, as it has very little place in gunsmithing (even less than a dremel tool).
      The proper way to cut threads in a barrel is to mount the barrel in a double spider and make certain that there is not too much tension on the aluminum tipped bolts.
      You line the bore up with a range rod (PTG sells a complete line of these rods and they are inexpensive and very helpful).
      Once the bore is running true within .0005, you cut the threads with a very sharp cutter and use three wires and a micrometer to precisely gauge your pitch diameter. What you are looking for is the big side of a class II fit. Assuming you are using the .0206 wires, that would be an “over the wires” measurement of .5060.
      Next, before removing the barrel from the lathe fixture, you reinsert the range rod and check for alignment. Once you are very very sure that everything is as straight as you can make it, clean the thread seat perfectly flat, and then the barrel face at 90 degrees.
      Finally, set your compound on 45 degrees and install a sharp carbide boring bar.
      Break the leading corner of the threads about .050 by running the lathe in reverse and cutting on the back side, then throw it in forward CCW and clip the corner of the bore just enough to clean up the rifling lands and leave a slight bright ring.

      Without moving anything, screw your suppressor on the threads and put an indicator in the exit hole. if it does not run true, find the source of the trouble and correct it. You want to be able to seat the can and break it loose and have it return to an exit hole runout of less than .010 three times in a row.

      I can’t agree more. The welder has no place here. Sounds like Goodsteel has a grasp on proper lathe operation so I won’t comment any further on that. Follow his recommendations and your weapon will once again shoot true.

    • #23139
      Goodsteel
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      That’s brilliant.

    • #23141
      Alphawolf45
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      Of course Goodsteel is correct but if the OP will follow my advice he can be out shooting while he gets his tools and skills together and then cut the barrel shorter and do it correctly at the time of his choosing…Of course I am presuming he is short on tools and skills since he admitted to twice messing up threading with lathe…I being a tool and diemaker by trade would not have admitted to it Hehhehehheh

    • #23143
      blademasterii
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      Being a welder fabricator with only minor lathe skills it was something I was willing to attempt my way because the worse case scenario for me was cut the threading off entirely and recut it all. Which was going to have to happen anyhow with the threads that were there. I had them cut 15 years ago and they were the wrong pitch for my suppressors and the adapter looked stupid and added even more length. Boreing out the rifleing was in my mind as well as a temporary fix. I am slowly getting everything done to get my garage built. Got the funds but the county is being a pain for permitting. Once I have that i’ll work on a decent lathe for this kind of work. I am using the lathe at work right now and it never was a great lathe even new. I have shortened, threaded and crowned an ar15 barrel for my sbr to use as a .22 upper that shoots better than it should. I would never call myself a gunsmith based on what I am capable of doing and or fixing, but any work I feel capable of doing myself I will. Of course that has meant replacing a few things here and there but not very many and the knowledge gained succeed or fail made the attempt worthwhile.

    • #23148
      Goodsteel
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      If you want, I can cut those threads for you. I have all the tools mentioned above and I’m used to using them.
      If you want to take another crack at it, ask questions here and we can get you lined out.

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