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Thread: Shim for barrel timing?????

  1. #1
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    Default Shim for barrel timing?????

    I am nearing completion of my third (and last) HighWall type SS rifle and I guess I screwed up by not torquing the barrel down enough when setting up the head space and extractor. The problem is that after removing the barrel a couple of times it now does not torque down tight enough to make me feel comfortable with it and still maintain the proper timing, I suppose High strength Loc-Tight or stud&bearing mount compound would hold the barrel securely enough since it's really not "loose" just torqued too lightly to suit me. Milling the shoulder at the barrel stub to set the barrel back would require a full revolution and .062" back since the extractor and Breech-Block cutouts would need to be in the same positions and of course the head space would need to be reset and the chamber reamed a bit deeper, as if that is not enough it's an octagon barrel and setting it back that far would mess up the ends of the flats where the barrel meets the receiver. What I propose to do is deepen the normal recess for the barrel seat into the receiver by .030" and then make a spacer/washer about .035" resulting in a net gain of .005" over the uncut barrel seat, that .005 is just a guess as to how much would be needed and likely would need "adjusting". Setting the barrel back presents a host of problems that I would really like to avoid and locking compound just seems like a "shade-tree" solution (but then maybe not?) so I hope I am making sense with my explanation of what I am thinking of doing, I would like some opinions on doing this. Good idea or bad? Assuming this is a viable solution to the problem should the spacer/washer be harder or softer than the 4140 HT of the receiver and 4140 barrel? Other suggestions?

    BTW, the spacer/washer would be precision ground to spec using a surface grinder.

  2. #2
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    There are a couple of ways of tightening up the draw up of a barrel. The simplest is to peen the breech end enough to stretch the breech at that point. If done with care, it can be draw filed so it won't show. A simple shim will also work, it need not be as involved as your plan, but if that is the way you choose to proceed, I see no problem with that as long as it does not increase headspace.

    As long as the draw up is snug, I also see no problem with loctite. There are many high quality take down rifles that make up hand tight with some mechanical means to prevent unscrewing.
    Jim H.

  3. #3
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    While it's not on the same level as your project I have done something similar in the past. I wanted to put together a pile of spare parts that included a 1903-A3 Remington receiver that looked like someone had taken a dull wood rasp to the front receiver ring for some unearthly reason. I faced off the receiver wanting to install a NOS 2 groove Remington barrel that I had as well. I made a spacer from plain steel shim stock that gave me just the right amount of crush to align the index marks. No thread locking compound at all and it's never budged. It turned out to be the most accurate '03 in my stable too. I never would have guessed that.


  4. #4
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    I knew one of the old time bench rest gunsmiths out in CA (Harvey Miller) who never torqued his barrels much more than hard hand tight, and relied on Loctite to keep them from moving.
    David Kaiser
    “You can have peace. Or you can have freedom. Don't ever count on having both at once.”
    ― Robert A. Heinlein

  5. #5
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    Maybe I have been over thinking the problem and placing too much importance on a rather tight fit, I have been basing this on the fact that every factory barrel I have ever removed (with the exception of some rimfires) have been so tight as to almost seem welded in place so I assumed that to be the standard way of doing it. I first thought about using just shim stock but past experience with thin shims only a few thousandths thick under a sliding/twisting surface, for example under a bolt head as a washer, has been extreme distortion and usually galling of the material so that's why I was thinking of using the spacer ring instead. Maybe I should just save myself some trouble and rethink the Loc-tight?

  6. #6
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    I never could understand why people tighten barrels to the point of stressing. This is right over the cartridge and at the highest pressure point. I use low strength locktite. Never had a loosened barrel and they all hold good groups.

    I vote low strength locktite. If you use high strength whoever takes it apart will not say kind words about you and your ancestors.

    Bob

  7. #7
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    include a little written comment on the barrel channel of the fore stock that the barrel is secured with a thread locker? Then they know that they need to heat it up to soften it and allow coming loose. Or notes on a little history card that fits in the shoulder stock behind the butt plate?

  8. #8
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    The low strength blue and lower strength purple don't need any heat. They can be turned with the proper tools. Blue is the norm for gunsmithing. Purple is for very small screws, commonly used on circuit boards and electronics. I use blue on revo barrels that are hand tight and they never come loose.

  9. #9
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    Radkins: I realize that this is after the fact on this particular project, but it might come in handy on the next one. That is to use a bit of lapping compound when going for the final fit on the threads. Do this a couple of times and you will take out the "high spots" in the threads. This is not only good for gun barrels, but lots of other "fits".

    Sarge

  10. #10
    Join Date
    Jun 2013
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    Quote Originally Posted by radkins View Post
    I am nearing completion of my third (and last) HighWall type SS rifle and I guess I screwed up by not torquing the barrel down enough when setting up the head space and extractor. The problem is that after removing the barrel a couple of times it now does not torque down tight enough to make me feel comfortable with it and still maintain the proper timing, I suppose High strength Loc-Tight or stud&bearing mount compound would hold the barrel securely enough since it's really not "loose" just torqued too lightly to suit me. Milling the shoulder at the barrel stub to set the barrel back would require a full revolution and .062" back since the extractor and Breech-Block cutouts would need to be in the same positions and of course the head space would need to be reset and the chamber reamed a bit deeper, as if that is not enough it's an octagon barrel and setting it back that far would mess up the ends of the flats where the barrel meets the receiver. What I propose to do is deepen the normal recess for the barrel seat into the receiver by .030" and then make a spacer/washer about .035" resulting in a net gain of .005" over the uncut barrel seat, that .005 is just a guess as to how much would be needed and likely would need "adjusting". Setting the barrel back presents a host of problems that I would really like to avoid and locking compound just seems like a "shade-tree" solution (but then maybe not?) so I hope I am making sense with my explanation of what I am thinking of doing, I would like some opinions on doing this. Good idea or bad? Assuming this is a viable solution to the problem should the spacer/washer be harder or softer than the 4140 HT of the receiver and 4140 barrel? Other suggestions?

    BTW, the spacer/washer would be precision ground to spec using a surface grinder.
    i know a couple of benchrest shooters/gunsmiths that would screw there barrels on by hand, seating the last thread with a quick twist and then shoot them like that. you couldn't unscrew it by hand. the trick to this of course is having threads a little on the loose side and lets the shoulder fit up tight. some smiths insist on fitting threads so tight that you need to use a wrench to install the barrell, i never understood the reasoning behind this. i shot benchrest for years and probably never used more than 20 to 30 ft lbs to tighten a barrel (guesstimate) if your barrel is seated firmly to the receiver i would leave it alone and i also would not be afraid to use some loctite if you require more peace of mind.too much can go wrong by fooling around with shims now. and i definitely would not modify the receiver. if this is your gun you could cut the barrel tennon back far enough to make a decorative spacer to correct your barrel timing and most people would not be the wiser, but this is not the type of thing to do with a customers gun without his blessing i would be interested to know how you make out. best of luck==

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