Chamber dias on late NMBH (large frame) 45 Colt

[Onty]

Just located Bisley 45 Colt, blue, 7.5" barrel. excellent condition. According to serial number (47-12XXX), revolver was manufactured 1986, see https://ruger.com/service/productHistory/RE-NMBhawk45 . The problem is that many of those earlier Ruger 45 Colt revolvers had issue with oversize chambers, .486" to as much as .490", and chamber throats .457" to ,458" (see article "The .45 Colt - Dissolving the Myth, Discovering the Potential by John Linebaugh", https://www.johnlinebaughcustomsixguns.com/writings ). According to John, Ruger did later correct this issue with chamber dias, and gentleman from another forum stated that correction in manufacturing process was done 2010.

Since I don't want to buy revolver with grossly oversize chambers blindly (revolver is located about 10 hours straight drive), I was thinking about contacting seller and sending him plug gauges and asking to check chambers and chamber throats.

In that respect, I would appreciate if somebody who purchased NMBH (large frame) 45 Colt, manufactured 2010 and after, could check chambers and chamber throats, so I could make my gauges accordingly. Please check these two diameters:

Thanks for help!

 

[NikA]

While I understand your desire to have correctly sized chambers and throats, why make the gages to a manufactured sample spec rather than the correct sizing for your intended use?

For instance, most here would say .4525-.453" would be correct for the throats with .452" bullets.

I don't believe I have access to a post-2010 NMBH, could look and measure this evening.

 

[NikA]

2016 .45 Colt Redhawk:
Back of chambers ranged from .4820" to .4823"
Front of chambers ranged from .4808" to .4810"
Measured a few throats from .4515" to .4525", remember possibly fire-lapping this gun.

2009 .45 Colt Blackhawk:
Back of chambers ranged from .4817" to .4818"
Front of chambers ranged from .4815" to .4817"
Measured a few throats at .4525"-.4530". Almost certain I lapped the throats with a brass lap and diamond paste.
Only measured 3 chambers on this one, all adjacent.

Not sure if these tell you what you want to know. Both examples are tighter than SAAMI spec per my measurements. SAAMI specs chamber diameter near base at .486"+, with a taper down to .480" at the case mouth.

 

[Onty]

Thank you Sir for remarkable data. This is exactly what I am looking for.

Chamber throats are not big issue, you are right about sizing bullet. The issue is chamber dia where case goes. My intention is to use close to "Ruger" 45 Colt loads. If chambers are large, cases will bulge, and their life will be short.

 

[Ale-8(1)]

I've had all my OM .45's reamed to 0.4525" and they work great.

 

[Hvymax]

I didn't know that there's a Drop In Auto Sear for the Blackhawk???

 

[gunzo]

"Close to" Ruger only loads won't have the gun or any decent brass even breathing hard. About the only thing that will be off on an '86 model might be the throats. And they'll likely be small if untouched. Easy fix.

 

[Hvymax]

This reminds me of the accurizing method for 1858 Remington's. The barrels are 45 caliber and the cylinder 44 caliber so the swaged to fit balls were too small to properly engage the barrel. Reaming the cylinder to the proper diameter increases accuracy considerably.

 

[George]

I have a 2017 stainless steel two Ginger prefix mid-frame Blackhawk convertible, chamber size on the colt cylinder is standard size however most of my Ruger 45 Colts cylinders have tight throats! Easy fix but I'm not that fussy! I checked it against a 2002 large frame! Same issue with the throats cylinder where the cases ride are the same, not oversize on my guns. No bulging from mile to Wild, and wild in the large frame is Ruger only loads!