Reaming .357 Mag throats to .359

[barnfrog]

The groove diameter of my Ruger Blackhawk is 0.3585". Four of the cylinder throats will accept a .358+ pin gage and the other two will accept a .359- gage. I'd like to ream them all out .359 to make them all the same. 4D rentals says their .357 cylinder throater will ream the throat to .358, as does every other throat reamer I can find. 4D also says their .357 reamer comes with pilots from .354 to .359. Why would you need a .359 pilot if the reamer only reams to .358? I'm not a machinist, so there may be something I'm missing.

More importantly, short of trying the Bubba gunsmith method of chucking a dowel with emery cloth in a cordless drill (which I am loath to do), is there a proper way to open all my throats to a consistent .359 if the only reamers available will only open them to .358? Or is the existing inconsistency among my throats insignificant since it's somewhere in the neighborhood of +/- .0007"?

 

[Kp321]

I seriously doubt you will be able to see the difference if you can get all the throats to .359”. The most important thing is that the throats are as large as the bullet diameter.

 

[Jim Watson]

Doug Guy on Cast Boolits and Cylinderhone on FB normally cuts to .3585" but will apparently go larger on request.

https://castboolits.gunloads.com/member.php?29606-DougGuy

https://www.facebook.com/Cylinderhone-756429174391912/

 

[.38 Special]

In the OP's I probably wouldn't bother. It's unlikely to improve accuracy in any detectable way. If I'm looking for the last shred of performance - and I am able to outshoot the gun - then I'd shoot some groups with the "perfect" chambers and see if that shows measurable improvement. If yes, then I'd consider it, but otherwise...

 

[dannyd]

Unless all you do is shoot from a Ransom rest that little bit of difference will never be noticed.

 

[barnfrog]

Thanks for the advice. I'm holding off on the throat reaming, but have been told dressing my forcing cone might be advisable. People recommend 4D Rentals, but once you add shipping it's almost as cheap to just buy a cutter: https://pacifictoolandgauge.com/rev...l-45-cal-11-revolver-forcing-cone-cutter.html.
Problem is, they don't sell the pilot bushings to go on the T-handle. The helpful lady at Pacific says their engineer indicates bushings aren't necessary, but that seems a little risky to me. Even if the cutter is self-centering I would think you'd want a bushing at the muzzle to make sure you're keeping the handle straight. Am I over-thinking it?

 

[gwpercle]

Doug Guy on Cast Boolits and Cylinderhone on FB normally cuts to .3585" but will apparently go larger on request.

https://castboolits.gunloads.com/member.php?29606-DougGuy

https://www.facebook.com/Cylinderhone-756429174391912/

Great Advice Here .
I can vouch for Doug Guy's work , top drawer and knows his stuff .
Gary

 

[Ru4real]

Will the six shooter put all 6 rounds inside an inch at 25 yards from a rest?

In order to meet this goal, I’ve had to do combinations of throat and forcing cone work on several of my revolvers including S&W, Ruger, Colt and Kimber. Making all the throats the same has been necessary for me to get there.

I’ve had only one revolver make the cut without my tinkering, which is the 586 no dash 8-3/8” below. The 2018 production 586 took 2 years of off-and-on tinkering, but I got it there, also shown below. I’ve had two revolvers that were close but still needed tuning: Ruger BH hunter and S&W Model 25, both in 45 Colt.

Based on my experience, if you can get there, you will not have a lot of company, regardless of what you read on the inter-web, lol.

View attachment 1146039


Here is the Ruger BH Hunter in 45 Colt. I put a scope on it to see which bullet “flew better” at 100 yards. I like the MBC 325 Slammer in 45 Colt (312gr actual weight). The Cast Performance bullets shot a little lower. Five MBC’s in a three inch circle at 100 yards from a revolver? What’s not to like

View attachment 1146040

View attachment 1146041

 

[barnfrog]

Will the six shooter put all 6 rounds inside an inch at 25 yards from a rest?

Negative, but I am aware that 1" at 25 yards is a tall order for a standard New Model Blackhawk. I have gotten a couple groups under 2" during my load work ups, but they were not repeatable. The best I've been able to do consistently is 3". I think the standard for a Field Grade gun is 2.5". I would be happy with 2".