Cylinder throat reaming question

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IlikeSA

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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?
 
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?
 
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.
 
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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.
 
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.
 
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.
 
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
 
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.
 
I guess I have my next project. Thanks everyone! Mixed Nuts, I'd still like to hear how your shooting went.
 
shooting lead)
Hornady 158gr XTP
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
 
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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)?

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.
 
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
 
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!

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.
 
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:
View attachment 796379

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.
 
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.
 
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