Barrel Groove, Cylinder and bullet diameter for .45 Colt

[Milt1]

I have a Ruger Blackhawk in .45 Colt that I've had trouble with in coming up with accurate handloads.
My understanding is that if the barrel groove diameter is .451 then the bullet diameter should be .452 and the cylinder throat should be .4525 or .453. I have been told that for the past decade that Ruger's barrel grooves for the .45 Colt has been at .451. I haven't had my barrel slugged to see what it measures. I checked my cylinder throats with a micrometer (probably not the best way but the only thing I had) and they measure consistently at .450. If my measurement on the cylinder is accurate and the barrel groove is at .451 then it seems that the cylinders need to be opened up at least to .4525 or .453. What are my fellow THR thoughts on this?

 

[ACES&8S]

I have a Ruger Blackhawk in .45 Colt that I've had trouble with in coming up with accurate handloads.
My understanding is that if the barrel groove diameter is .451 then the bullet diameter should be .452 and the cylinder throat should be .4525 or .453. I have been told that for the past decade that Ruger's barrel grooves for the .45 Colt has been at .451. I haven't had my barrel slugged to see what it measures. I checked my cylinder throats with a micrometer (probably not the best way but the only thing I had) and they measure consistently at .450. If my measurement on the cylinder is accurate and the barrel groove is at .451 then it seems that the cylinders need to be opened up at least to .4525 or .453. What are my fellow THR thoughts on this?

You are right , 45 Colt they should be easy to make accurate.
Only way I know to check the cylinder measurements you did is to take a loose 45 caliber
.452 brass jacketed bullet & see if it will easily drop into the exit end of the open cylinder.
That should tell you if ammo is ok.
Do your brass reloads feed ok?
That's all can think of.
Love those Colt 45 revolvers.

 

[Milt1]

I have a factory jacketed bullet that mikes at .451 and it goes thorough the cylinder throats with just a tad bit of pressure. I also tried lead bullets that mike at .453 and .454 respectively and there's no way that either will go through the cylinder throat. The lead bullet that mikes at .453 was supposed to be at .452 but it isn't. It's from Bayou Bullets and I'm thinking their coating left it at .453 rather than .452. Based on my findings with the bullets, I think, if my barrel groove diameter is .451 and I'll try to verify that with Ruger, then the cylinder throat should be enlarged to .4525 or .453 and that would enable me to shoot a .452 bullet which should fill a .451 barrel so that there are no gas leaks around it.

 

[murf]

your cylinder throats are larger than .451" and should be fine for any bullet diameter of .451" and above. the groove diameter of the barrel must be smaller than both the throat diameter and the bullet diameter (don't shoot .450" diameter bullets!).

the .451" dia. bullets should shoot fine. i would load up a dummy round (no powder or primer) and make sure it will fit the chamber (the rim must touch the back of the cylinder). if the dummy round passes the test, then load em up and shoot em.

if you get leading, the problem should be somewhere other than the diameter of the bullet and throat.

luck,

murf

 

[ReloaderFred]

You need to slug the barrel to find what the diameter is. Ruger can't tell you that, since they vary, depending on the wear on the broach that was used on the barrel at the time it was made. You also need to measure the chamber throats, and that's done with pin gauges. Ideally, the throats should be .4525", which should work perfectly for .452" diameter cast bullets. Jacketed bullets are more forgiving than cast, but once cast bullets are properly sized and lubed for the firearm they're going to be used in, they will equal, or exceed the accuracy of jacketed bullets.

Hope this helps.

Fred

 

[Catpop]

Jacketed bullets or lead boolits?
Boolits need to be .002 to .003 over bore AND should slide (not fall) through throat.
RUGER is known to have the throat to small (swages boolit) for best boolit accuracy. Sounds like your issue.
Rugers usually work fine with jacketed.
I speak from experience with my Rugers.

 

[highlander 5]

The problem I ran into is where the barrel is screwed into the frame. It's a crush fit and that caused a constriction at that point,fire lapped the barrel and all's right with the world. Had the chamber mouths opened to .453 also.

 

[CraigC]

The most important thing is, how does it shoot? If a .451" jacketed bullet passes through, I'd be skeptical that the throats are the problem.

 

[mdi]

"Drop through", "snug fit", "push through" aren't measurements. If you're looking for accuracy, being accurate with measurement is necessary. So, slug the cylinder throats, just like you would slug your barrel or use pin/plug gauges. Slug the barrel. Measure both slugs with micrometers. The cylinder throats must be larger than the groove diameter of the barrel, preferably at least .001" and .002"+ larger is better.. If you shoot lead bullets they must be larger than the groove diameter and .002" is a good place to start. If the cylinder throats are smaller than the groove diameter, leading will occur and accuracy will suffer. Size, or purchase lead bullets to the same diameter as the cylinder throats (larger and the throats will size the bullet down as it passes through and smaller can result in leading). For jacketed bullets, bullet diameter is best at groove diameter or .001"-.002" larger, but the manufacturer pretty much controls jacketed bullet diameter.

These are just starting points as I've experience them and not carved in stone (I've used jacketed bullets .003" over groove diameter and occasionally lead bullets under cylinder throat diameter, but the above will get you started in finding an accurate load...

 

[Charlie98]

Mismatched or undersized cylinder throats, and the 'torque bulge' in the barrel are fairly common on Ruger wheelguns. I would start by having the cylinder throats reamed, just to even them up and rule that out, then you can check the barrel for a bulge. Run a very tight fitting jag/patch combo down the barrel, if you hit a restriction (just in front of the forcing cone, where the barrel is threaded into the frame) then you have a barrel bulge.

I had the same problems with my .45 Vaquero and a .44 Flattop...