I’m wanting to shoot cast in my (new to me) Ruger BH convertible. Sent both cylinders off and had them opened up to.452. I have some Hunters Supply 250 gr. FPs sized @ .452.
How much resistance should I encounter getting said bullets to pass through the newly honed cylinders. I’ve miked the bullets @ .452. Checked the cylinders with calipers and they check.452. With a dowel rod and mallet it takes several sharp raps to drive the bullet through the cylinder.

When the big light hits the base of the bullet, they’ll slide right through.

It is very hard to get a proper reading using calipers. You really need plug gauges, which I can lend you as I have done here in the past. That said, I would just shoot it and see.

The critical relationship is the throats with the bore. If your bore is bigger than .452 you may still have trouble getting accuracy. What does your bore mike at?

Well I haven’t actually slugged the bore and I’m assuming that’s what you meant when you asked what it miked at. That’s on the agenda for today if I can find some pure lead egg sinkers in my fishing stash. Haven’t used any of them in a long time but I’m sure I had some somewhere.
I’ve ordered a Lee .452 sizer die for these bullets as they’re crowding .453 unless you really snug the mike down tight. I may be making a mountain of a mole hill but then getting there is half the fun right?

Seat them over 8 or 9 grains of Unique and shoot a few groups. You might not have a problem.


Okie John

For what it's worth, here is my experience. I have a 1978 Ruger Blackhawk. It's bore slugged .451, and the cylinder throats were .455-.456. Accuracy was okay, but nothing special. I returned it to Ruger to get a steel grip frame, and while there I ordered a new cylinder. The new cylinder throats slugged .450. I had it opened up to .452, and my accuracy with .452 cast bullets is fantastic. I use a Lyman .452 sizing die, mostly on the 250-grain Lyman 452190 bullet, cast from 1:20 alloy. I used .490 lead rounds balls for slugging, tapping them into the front of the cylinder and then back out with a steel rod.

I'd leave 'em at .453 and try them with a proven load first. A thousandth oversize is nothing to sweat.

Nothing wrong with leaving them .453

If I'm remembering right from my days in machine shops, identical diameters on the hole and plug are considered a press fit. Especially since both are likely to be slightly out of round. We figured an alignment pin needed to be 2-3 tenths smaller to allow reasonably free engagement.
This doesn't even take into account the bullet diameter increase after getting slugged in the butt upon pulling the trigger.

Back hen "Dirty Harry" was rampaging through the criminal element of San Francisco there were no 44 Mags of any make available. I read an article in one of the gun mags that the 45Colt out of a Ruger Black Hawk would do most anything the 44 Mag out of the Super Black hawk. So I bought a Black Hawk with a 4 and a half or what ever the length of the barrel was I tinkered with he handgun for a year or or so, reading every thing I could find. I started resolving issues one at a time. Soft commercial swaged lead bullets were a gun cleaners night mare. I switched to linotype bullets with Lyman bullet better but still leading. Read an article about the constriction in the barrels forcing cone that needed to lapped. That helped, but still leaded. Then I read another article about using .454 diameter bullets an alloy of 80% wheel weights and 20% linotype.
Then I started tinkering with different powder charges, seating depth. crimping and found my preferred load Then LBT came on the market, or it came to my attention and I found the one perfect and holy load for my Black hawk. The I discovered S%W model 25s. I took the new arrival out of the box polished all the moving parts for a nearly perfect trigger. Then I measured the cylinder mouths mostly .453 and a bit. Pushed a soft lead bullet through the barrel and found the barrels forcing cone needed lapping and did so. I used the same recipe for the S&Ws and gave the Ruger to my daughter to hold for my grandson. Have fun I tinkered with shot loads for the Ruger not one of my more successful experiments. put three ;ead balls, using Styrofoam for wadding and candle wax for holding the balls in the cylinder. this was a fun project for winters evening. If you take up bullet casting I'd suggest buying two four cavity molds, preferably Saeco, Lyman or one of the new custom mold makers. I found 250 or 255 grain bullet weight. Now this will lead you into other avenues of bullet casting Voodoo Hoodoo requiring you to purchase a 45 -70 lever action. A 250 grain grain 45 caliber bullet with 13 grains of Unique behind it makes a heck of a squirrel load.
Have fun

If the throats in your Ruger have been opened to .452 and the bullets are .452, .453, or .454, the results will all be good and basically the same. I run bullets .002 over throat size all the time.

Only issue I can imagine encountering is maybe if the driving band was really far forward and it hung up in the throat when you loaded the gun.

It sounds like you are trying to fix a problem when you don't know if there is actually a problem.

Before making modifications to improve the accuracy, go shoot the gun and determine if it actually needs anything done to it or not.

Slugging bores and doing the things you are discussing is what you do AFTER you have discovered that the gun does not shoot well.

^^^This^^^

Concur.

I expect it will shoot well. I have a 1980 New Model Blackhawk through whose forcing cones a .452” 265 gr WFNGC bullet slides through with almost no resistance. I haven’t measured the cones precisely, but they are factory. I find that 21 gr/296, new Starline brass, Federal 155 primer, shoots very small groups. A bit smaller than the same bullet with 8 gr/Unique.

Point being, your gun sounds quite similar and will likely shoot well with good bullets and a decent load. Do not expect the old soft lead 250 gr round nose bullets to shoot well; they are horrible in my revolver. Same for the cowboy action loads.

Having shot various 45 Colts over the past 50 years I learned a couple really important things don't use soft swaged bullets and size all home made bullets .454 / and if you can find them buy factory made bullets sized .453. I've not fired any of the powder coated bullets through my 45 Colts , have no idea how they function.