Crown polishing?

Discussion in 'Gunsmithing and Repairs' started by daniel craig, Jun 8, 2021.

  1. daniel craig

    daniel craig Member

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    111C0F26-293E-49F7-AD5D-A26AB6E151BF.jpeg AADEE5D1-C1F4-41E8-B002-D146D01E2BB5.jpeg
    Ok, so. On a rifle I had cut down and crowned a while ago, I had an 11 degree target crown put on. It wasn’t that well done in the first place but I also hadn’t taken care of it. How, without any special tools, would you suggest I polish it for a smoother finish?


    Edit: would you recommend a recessed crown or aren’t they necessary?
     
    Last edited: Jun 10, 2021
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  2. earlthegoat2

    earlthegoat2 Member

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    First a question: Are you having any problems with the rifle that could be related to the crown?

    You can polish the muzzle out with nothing more than a marble and some valve grinding compound and about a half hour of work. That can improve things.

    Lapping paste and a rounded lap that you chuck into a drill would expedite the process. You can get that here.

    https://www.brownells.com/gunsmith-tools-supplies/barrel-tools/muzzle-lapping-tools/power-custom-brass-muzzle-crowning-lap-prod855.aspx

    https://www.brownells.com/search/index.htm?k=Lapping+compound&ksubmit=y
     
  3. Demi-human

    Demi-human Member

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    Just to polish, I’d use some metal polish and a cloth.
    But I’m not sure how well a glinty polished surface might work out hunting.

    I have done a few handgun barrels with a dremel wheel and polish. Not so worried about affecting something there.

    If I wanted to change to shape, a hard surface would be better. A domed carriage bolt in a drill or an old billiards ball could suffice in a pinch.

    A good firearm deserves a quality tool though.
    A poorly done job is a pain, twice.:)
     
  4. J-Bar

    J-Bar Member

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    Rednecks would use a spherical grinding bit on a drill if it were on anything but a bench rest competition gun. Done it my own self to polish out a ding on the bore’s edge. But probably should only be considered an emergency or temporary fix. Best left to a good gunsmith.
     
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  5. Bfh_auto

    Bfh_auto Member

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    Pan head brass screw and valve grinding compound.

    Do a little research on that.
    I've done it and it works.
     
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  6. Mk-211

    Mk-211 Member

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    I'm with Earl, are you having issues? If not, you could make things worse.

    It looks like the bore is square with rounded corners. At least that's what I'm seeing, anyone else?

    Have you contacted the person that did it? Can they redo it and make it look correct?
     
  7. Odd Job

    Odd Job Moderator Staff Member

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    Agree with the others: don't mess with the crown. If you do, send it out to someone who can do the work perfectly aligned with the bore.
     
  8. ColtPythonElite

    ColtPythonElite Member

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    I have done it several times with good results
     
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  9. chicharrones

    chicharrones needs more ammo

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    I've done the brass round head screw and polishing compound trick as well. The screw should be large enough to fit the crown, and unless you hamfist it, a simple polishing shouldn't change the crown squareness.

    However, a round head brass screw may dish out that 11 degree crown a bit, so I might be inclined to see if I could just polish it with polishing compound on a cloth bore cleaning patch supported by my thumb. And rotating my thumb as if it's on an axis with the bore.

    Afterward, you can put many applications of cold blue on the polished crown to get it to look more like the rest of the gun. It seems like cold blue does pretty well on a crown, in my limited experience.
     
    Last edited: Jun 9, 2021
  10. edwardware

    edwardware Member

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    Presuming you mean "dress the intersection between crown and bore". . . because there's no reason to polish the crown unless you're refinishing the barrel. . .

    A brass pan head screw and a gram of Clover compound is perfect. If the crown was cut off-center you can't fix it, but you can dress the edge perfectly well. The screw head should be 1/3 to 1/2 larger than the bore.

    I will have to try the marble. . . first I've heard of it. How do you turn it?
     
    Last edited: Jun 9, 2021
  11. LoonWulf
    • Contributing Member

    LoonWulf Contributing Member

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    Ive used pan head screws and fine valve grinding compound, counter sinks.....other stuff. 99% of the time they have worked fine, the 1% was usually cause i rushed.

    That said easiest and cleanest method is with a crowning tool. I rent one from 4D from time to time when i have enough projects to make it worth while.
     
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  12. Bfh_auto

    Bfh_auto Member

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    I use the a drill.
    I've heard of a marble. But haven't tried that before.
    I also don't jack with the crown unless it's the last option. Or if it's obviously terrible.
     
  13. doubleh

    doubleh Member

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    I have used the brass screw to true up a dinged crown with good results. Owning a small lathe and having self taught myself to do very simple things with it I have made two lapping tools from brass rod to handle small and large bores. I just cleaned up a brand new barrel that was showing a small problem at one land. The groups improved by about a third after the clean up with Clover compound. I have also recut a few crowns with the lathe and lapped with compound after the cut with improvement on each.
     
    Last edited: Jun 11, 2021
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  14. GBExpat

    GBExpat Member

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    I truncated a few barrels (as I recall, one pre-built CETME C Variant and several of my home-rolled FALs) and finished them with an 11° crown.

    Once I completed each crown, I was primarily interested in removing the knife-sharp outer edge. I used 400, 600, 800 and 1200 sandpaper to civilize the area.

    I started with the 400. With a sheet of rubber lying flat on the bench and the sandpaper on top, I carefully pressed the crown to the sandpaper and rotated the barrel to remove the sharp edge. After that I used successively finer grades with my rotating thumb to apply the pressure. That cleaned-/polished-up the face quite well and never actually touched the bore edge.

    As chicharrones suggested, cold blue does a decent job as a final touch-up. :)
     
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  15. Demi-human

    Demi-human Member

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    By hand only until the lands have been chamfered back to a good crown job already. Or so I’ve read.:D

    I thought about doing it to my Savage, but that probably won’t help, and definitely won’t reach the marks from the crowning tool pilot. (That must have been in want of lubricant…)

    It would take much polishing to detrimentally affect that crown, but I’ll still not chance it based on how it shoots now.


    Pistols? That’s an aesthetic thing.:thumbup:
    Rifles may be aesthetic too, but I’d have to weigh the situation.:D
     
  16. daniel craig

    daniel craig Member

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    Honestly with how accurate this rifle is right now I don’t really know if problems are crown related or not. I just feel like polishing it would be kind of a fun hobby to do and only runs the risk of helping me.
     
  17. daniel craig

    daniel craig Member

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    I get what you’re saying but it’s a mosin that’s already been cut up and packed away at. It’s kind of my practice doing gun work done as well as my hunting gun.
     
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  18. daniel craig

    daniel craig Member

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    Yeah I’m really not trying to change the shape I’ve heard that an 11° crown is pretty good. I’m just trying to make it smoother because in my non-gunsmith brain I feel like making it smoother might help.
     
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  19. Bfh_auto

    Bfh_auto Member

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    Don't fix what isn't broken.
     
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  20. BRatigan

    BRatigan Member

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    In my experience crowns are recut on a mill. You want absolute perfection in this process. Any good machinist can accomplish this task. Your best bet would be a good gunsmith with the appropriate tools for the job.
     
  21. jmorris

    jmorris Member

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    If you like the way it shoots, I would suggest you just quit looking at it.
     
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  22. daniel craig

    daniel craig Member

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    Well, It’s fine the way it shoots, not excellent but good enough. Was just wondering if this might help. I suppose it doesn’t matter, I mean it’s a mosin for Christ sake.
     
  23. jmorris

    jmorris Member

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    It might but it also might make it shoot worse.

    What the odds are for either outcome largely depends on the tools/hands used to do the work.

    If you would be happier if it looked better, even if it shot worse the risk/reward relationship is a lot different than, if how it shoots is more important to you than what the end, that is normally pointed away from your face, looks like.
     
  24. Bwana John

    Bwana John Member

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    That would bother me to the point I would have to "fix" it.

    If I fixed it worse, I would pay to have it "professionally" done, but I'm pretty sure I could clean that up without any detriment to precision or accuracy using just the bugger pickin method and some very fine wet and dry.
     
  25. P89DCSS

    P89DCSS Member

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    So you're saying a hand facer doesnt work?
    p_080586909_1.jpg
     
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