Taurus Barrel Crown

Discussion in 'The 1911 Forum' started by Balchinator, Mar 1, 2007.

  1. Balchinator

    Balchinator New Member

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    Hey Everyone,

    I just picked up a new Taurus 1911 I haven't shot it yet but one thing I'm worried about is my barrel crown seems to be cut crooked (kinda like they tried to chamfer the inside edge and messed up) and wonder if any one else has noticed this. If it shoots erractic I was gonna have it sent back but if it shoots fine I wasn't going to worry about it too much. Anyway I look forward to hitting the range this weekend and if anyone has some input that'd be great.


    thanks
  2. stash247

    stash247 New Member

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    If the crown looks nasty, it likely is nasty, and will so shoot!
    This is the last point in the barrel, at which the shooter has any input, and, so, is an essential, for accuracy.
    Had I any misgivings, in this regard, I would return the pistol, to the maker, and challenge them to re-assure me,with a 'test target'.
    Taurus offers a Lifetime Warranty, so this ought to be no big deal, with them.
  3. LDBennett

    LDBennett Well-Known Member

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    Taurus is not the only manufacturer to get the crown wrong. Me and several other Beretta 87T owners detected an off center crown on our guns. Not all 87T were off center, only some. Apparently some of the factory tooling was wrongly made and some of the crowns were done off center with the bad tooling. I just squared off a portion of the crown near the bore and then chamferred the bore down to the bottom of the grooves and slightly beyond with Brownell's brass spherical chamfering tool, grinding compound, and a hand drill per Brownells instructions. Gun shoots real well, now.

    Since the gun is so new simply send it back to Taurus to get it fixed. It can make a difference as the gas escaping on one side before the other might make the bullet yaw and not be dynamically fully stable (???). The key is the relationship between the end of the bore, both lands and groves and whether they are perfectly symetrical all the way around the bore. If not then the bulllets path may be affected. Use a magnifying glass to check this out.

    LDBennett
  4. Balchinator

    Balchinator New Member

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    Thanks for the input, susposedly taurus test fires them at the factory so im thinking it passed their criteria, but i know from shooting rifles the crown is pretty much a sacred part of the barrel so I wasnt sure if this is something thats come up before or even something they might do at the factory that has some sort of purpose
  5. stash247

    stash247 New Member

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    Your comments are accurate, LD, and to the point, as far as you went, but consider: The bore of the barrel, and it's outside diameter, for the length of the round portion MUST be concentric, for accuracy, and the termination of the lands and grooves, exactly perpendicular to the bore, for the same reason you gave, so as not to 'tip' the bullet with gas, at exit.
    The same tooling may well be used to both turn the OD of the barrel, and crown it, leaving the question of concentricity, unexplored.
    If you do not have a lathe, and a toolpost grinder, in your shop, any decent machine shop can turn, and grind a round rod to bore dimension, but 6" longer, and it won't cost much! Brownells used to sell 'range rods' designed to verify the firing pin as being in the center of the chamber, that might also be used!
    Mount the rod between centers, in a lathe, or clamp it in a vise, gently, by one end, with the barrel slipped over it, then indicate the barrel's round portion, end to end, at, say, half inch intervals, 360 degrees at each station; personally, a half a thousandth runout is the limit I would accept, in an 'accuracy pistol'.
    If the runout is greater on one end than the other, or greater on both ends than the middle, the bore is skew to the OD, will likely never shoot well, and the crown will 'look wrong', if worked from the bore, which is not centered in the barrel OD.
    I often spend as much as an hour, setting up a rifle barrel blank before contouring it, and work to a tenth, as a matter of honor, in my work, then do the same setup, barrel reversed, to cut the tennon, barrel thread, and chamber the barrel, and a third time, in the steady rest, to crown.
    If the barrel won't hold a thousandth, end to end, 360 degrees, you need a barrel, not a crown; all the paint in the world won't make a Princess, of a pig.
    Your thoughts may differ, and I address this comment not to LD, specifically, but to the list, as a whole. Should they differ, please speak up!
    I learn something new every day, or it would not be worthwhile
  6. LDBennett

    LDBennett Well-Known Member

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    stash247:

    What you say is very true IF you contour the end of the barrel into the classic rounded crown shape or use the now standard 11 degree target contour.

    But notice I said I "squared off" the end of the barrel. By that I mean I machine it off at a 90 degree angle to the bore centerline. If the bore is off center to the outside of the barrel then the cut I make is still 90 degrees to the bore centerline. I sometimes square it off then square a recess off closest to the bore, kind of like a flat bottomed counter sink, one of the common target crowns you often see on target guns. The Brownells chamferring tool is nothing but a brass ball loaded with griding compound on a shaft that you can turn with a hand drill, or hold by hand while the barrel turns in the lathe chuck. It makes the chamfer so that it centers on the bore not the outside of the barrel. The chamfer will end up concentric to the bore and the barrel end will always fade away from the chamfer at 90 degrees to the bore regardless of the concentricity of the outside of the barrel to the bore.

    The way I do it in my lathe is easy and makes the crowning (a target crown) concentric with the bore regardless if the bore is concentric with the outer barrel profile or not. Did I miss something you were saying? I think my way works too. If not it is not evident to me why it doesn't.

    By the way I use the chamfer tool with grinding compound to get rid of the burr that forms when I machine off the end of the barrel. I have never been able to make a cut across a hole without a burr forming no matter how sharp my bit, how small the cut, or how fast or slow I turn the work piece, but I'm not a machinist either. The grinding compound and the chamfer leave no discernible burr and a perfect chamfer.

    LDBennett
    Last edited: Mar 3, 2007
  7. stash247

    stash247 New Member

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    Bro, first, no mention of a lathe, in the previous post, so I was in the dark; If the crown is square with the barrel bore, not (necessarily) the barrel od, it may look eccentric, but it's the best one can do, with that barrel!
    If true, with the bore, AND the muzzle od, it looks good, as well.
    If the barrel is truly concentric, end to end, you have given a shooter the best he can hope for; the rest is on him.
    All the best, with a private message to follow, Terry
  8. LDBennett

    LDBennett Well-Known Member

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    stash247:

    I never seem to get the responses quite right. Normally I end up not only with a response but a proceedure and a history and....... My post tend to be wordy. This time I forgot to mention squaring off with a lathe (key point!) and your making mention of that oversight was right on! But my response was minimal. One of these days I'll get it right!

    Got you PM and sent response. Have a nice day!

    LDBennett
  9. stash247

    stash247 New Member

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    LD, and the rest of the crowd:
    As long as we continue to trade information and ideas, eithout insults thrown, or taken, we all grow in our knowledge.
    That's a GOOD THING.
    To steal an old friend's Sig line, the 'art of the spiral tube' is a huge subject, on which I know of no 'absolute' authority.
    I have persevered, for forty some years, to better understand the intimate workings of the .22 LR cartridge, and this is my first love.
    I have a 'day job', so this is my 'night time passion', but the love of my life, to build the most accurate rifles going, all that applies to this caliber, and rifles, extends to pistols, and other calibers, as well, as physics does not consider a particular application.
    I am fortunate to live in a machine shop, and sleep in a house, both with the same address, so my replies may seem odd, if you did not know the above.
    But, LD, I mean never to give offense, and almost never, take it.
    Please, all, continue to share your knowledge, as it is worthless, unless shared!
  10. LDBennett

    LDBennett Well-Known Member

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    Stash247:

    Good advice and the reason I am even here is to help and share. I wish no notoriety and only to help. I accept any and all question and response, but I do not always agree. But I do listen and try to learn. I absolutely do not have all or the only answers. We all should share as per Stash247 request.

    LDBennett
  11. 45Smashemflat

    45Smashemflat New Member

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    Good stuff guys - what I would wish to have access to the shops you guys have right handy! I'm lucky to have room for my table saw and the requisite tools required to work on a '78 Spitfire.

    Along those lines, if a guy was wanting to try his hand at some simple gunsmithing tasks - what recommendations do you have for some basic kit? Smithy Lathe that kind of thing?
  12. LDBennett

    LDBennett Well-Known Member

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    I have a Smithy and I am no machinist. The Smithy 1340 has made me many neat parts, mostly for Vintage motocross bikes that my son raced. But it is rather crude and the mill part of it is just OK with its problem being that it is not rigid enough for bigger work. I works OK for small gun parts. I did make a 6mm BR heavy barrel bench gun out of a Ruger Model 77 (gun of opportunity originally in 243). The Smithy did it all right but keeping it in alignment has been a problem. It is just a little crude for precision work like re-barrelling a heavy barrel bench gun. It also does not have a thread counter (newer ones may) but threading the barrel had me sweating bullets trying to instantly stop it (no brake) and back it up after a cut with it still engaged...not ideal. I'd never do it again. At least not on this lathe.

    LDBennett
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