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Cylinder throat reaming question

Discussion in 'Handguns: Revolvers' started by IlikeSA, Jul 9, 2018.

  1. IlikeSA

    IlikeSA Member

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    If you were happy with the accuracy but did not like the leading, would you ream the cylinder throats (knowing that they are a tight .451 for 45 ACP/Colt shooting lead)? Has anyone ever reamed cylinder throats to match bullet diameter and had accuracy degrade?
     
  2. jaguarxk120

    jaguarxk120 Member

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    What make/model revolver?
     
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  3. Walkalong

    Walkalong Moderator

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  4. IlikeSA

    IlikeSA Member

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    I kept up with the thread. The revolver is a blackhawk flattop convertible in 45 acp/colt.

    Usually reaming the cylinder decreases leading...but has anyone teamed a cylinder and lost accuracy?
     
  5. Mixed Nuts

    Mixed Nuts Member

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    I can, probably, let you know by Friday. I've just reamed a mixed size .357 cylinder to uniform .358s.

    I don't have the cast bullets I want to shoot yet but I've wondered the same thing - about accuracy after reaming - with factory, jacked ammo. So I intend to shoot 150 rounds of factory jacket .357 this week.

    A respondent to my thread on cylinder throat reaming said that he's never heard of a loss of accuracy from the reaming. So I'm optimistic. Perhaps six uniform throats at .358 will perform better with .357 than did the mixed sizes I had before.
     
    Last edited: Jul 10, 2018
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  6. IlikeSA

    IlikeSA Member

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    I look forward to hearing your results!
     
  7. Varminterror

    Varminterror Member

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    I have reamed throats and forcing cones on dozens of revolvers, would have to check books to confirm, but I wouldn’t be surprised if it’s been more than a hundred. Not a single one has ever lost accuracy.
     
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  8. IlikeSA

    IlikeSA Member

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    Thanks for the reply Varmitterror.
     
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  9. 200Apples
    • Contributing Member

    200Apples Member

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    I am presently neck-deep into this very thing with a few of my whirlenpoppers.
    I have discovered that there's more to it than merely reaming cylinder throats, although most do not consider that detail.

    Have you slugged the bore to determine groove diameter?
    When slugging the bore (one may also use Minus Gauge Pins), is there thread choke or other barrel constriction due to a dovetail (sights) cut?
    Is the forcing cone rough (do coarse machine tool marks exist)?

    I would also look into pressure-lapping your gun if leading and lack of desired accuracy continue to be an issue after you might size your throats. Beartooth Bullets offers all that is required for this admittedly tedious effort... but many notable folks swear by the results. Men like Brian Pearce, Ross Seyfried and of course Marshall Staunton of Beartooth extoll the virtues of pressure-lapping (fire lapping).

    Yes, one's hardcast slug should fit the cylinder throat. The throat should be slightly larger than groove diameter, and the whole affair should gently taper tighter in diameter to the muzzle for best accuracy.
     
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  10. Varminterror

    Varminterror Member

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    It’s really rare to see a revolver with an undersized bore. Contrarily, it’s exceedingly common to find undersized or inconsistently sized throats in production revolvers. Slugging the bore is a necessary first step, but I’ve yet to stumble across one where the bore was the problem. Discounting frame thread crush, naturally.
     
  11. Mixed Nuts

    Mixed Nuts Member

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    Hey, IlikeSA. Haven't forgotten this. Didn't shoot yet. Found a box of Hornady 158gr XTPs though. Loaded 60 rounds and put it with a couple of boxes of Federal stuff. Should go next week. Will try to report back on your question.

    View attachment 796244
     
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  12. IlikeSA

    IlikeSA Member

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    Thanks for the replies thus far.
     
  13. FROGO207

    FROGO207 Member

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    I have almost 30 center fire revolvers and I have reamed the cylinders in almost every one. I have not seen a decrease in accuracy using lead or jacketed in any one of them. 30 carbine, 32, 38/357, 44, 44-40, 45 colt.
     
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  14. IlikeSA

    IlikeSA Member

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    I guess I have my next project. Thanks everyone! Mixed Nuts, I'd still like to hear how your shooting went.
     
  15. 243winxb

    243winxb Member

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    This Old man confused? Leading and XTP?

    If the lead bullet makes it to the barrel from the cylinder and its the same diameter or .0005" larger then the barrels groove diameter, there will be no leading. When using a proper alloy and lube.

    Tested in my S&W M28 357 that has 1 tight throat. Groove dia .3575"

    Shoot a .3572" dia bullet, it will make leading.

    Now i have 3 - H & I Lyman sizing dies. 3575, 3579, 3581. :confused:
    full.jpg
     
    Last edited: Jul 15, 2018
  16. Arkansas Paul

    Arkansas Paul Member

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    If your throats are .451 I would think opening them up to .4525 would improve accuracy beause it's not gripping th,e riflings as well if it's swaging them down in the throats.
    It will also increase leading because of gas cutting around the base of the bullet, for the same reason mentioned above.

    Sorry if that is too elementary, you may already be aware of this.
    I can't imagine opening the throats to .4525 having anything but a positive impact on accuracy with cast bullets. It likely won't make a difference with jacketed.
     
  17. walnut1704

    walnut1704 Member

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    I've reamed, or had reamed, over a dozen revolvers and have never had the accuracy degrade after reaming.
     
  18. Varminterror

    Varminterror Member

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    Rereading this thread today reminded me of ANOTHER avenue of evidence which confirms my comfort in "regularizing" cylinder throats:

    1) I've done enough of my own to know it almost always helps, and never hurts.
    2) I've seen enough other gunsmiths who have done many which have never hurt

    and really the coup de grace...

    3) I have never even heard/read online of anyone who has regulated their cylinder throats and ended up worse
     
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  19. murf

    murf Member

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    no.

    luck,

    murf
     
  20. Ohen Cepel

    Ohen Cepel Member

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    Can one send a cylinder out to have it reamed and if so, suggested source for said work? Or, is it better to DIY and buy the reamer? Thanks in advance!
     
  21. Varminterror

    Varminterror Member

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    It’s better to send it out. Only cheaper to buy the tools and DIY if you have about 4-6 to do.

    Cylinder & Slide used to take it on. Cylinder Hone (aka Dougguy on a lot of forums) specializes in throat reaming - he’d be my go to, wanna say he was like $30-40 per cylinder.
     
  22. FROGO207

    FROGO207 Member

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    If you want to rent a reamer and DYI then 4Drentals has one for you to rent. I have so many revolvers that it was worth buying my own sets.
     
  23. Mixed Nuts

    Mixed Nuts Member

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    Hi 243winxb,

    The original poster has had leading problems with his revolver, and wants to ream his throats, but is worried that the work might effect his accuracy when shooting jacked ammunition.

    I'm going to shoot some jacketed stuff through a recently reamed security six to see if jacketed ammo has become less accurate as a result of the work.

    Not a big sample for testing, but it's the only modded revolver I've got.
     
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  24. TTv2

    TTv2 Member

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    Arkansas Paul is right that opening the throats will increase leading because there will be no gas seal and hot gases will blow by the bullet and soften the lead. The throats should be .0005-.002 smaller than the bullet diameter.

    If leading is the issue, use a bullet that uses a harder lead alloy.
     
  25. Varminterror

    Varminterror Member

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    ^nope.
     
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