I cut an 11 degree forcing cone into my 41 Mag revolver today. I have done this with some of my other revolvers and noticed an improvement in group size. Of course this works best for cast bullets but man, one can't say the smoothed up forcing cone, over the rough factory 5 degree cone, is not an improvement.
Took the photos before I polished it up.
Before
The tool
After
With rifle in hand, I confidently go forth into the darkness.
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Cutting the 11 degree forcing cone of my stainless 686 was easy, but my blue Blackhawk was more difficult and required way more pressure on cutter. Didn't help anything. Afterwards both guns still leaded around forcing cone area and accuracy was the same. They say powder coated bullets help prevent leading around cylinder face area.
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If your revolver leaded the factory 5 degree forcing cone, then it will also lead an 11 degree forcing cone. Alloy and pressure are the causes of leading. The 11 degree cone reduces the abruptness of a 5 degree cone on a lead alloy bullet allowing it to ease into the rifling. It also assists with the sizing of the bullet down a thou or two into the grooves. I have never cut a new cone to reduce leading, I change the alloy as appropriate.
It’s interesting to feel the different hardnesses of the cones as you pointed out. S&W seems the hardest to me.
With rifle in hand, I confidently go forth into the darkness.
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I have a pre-war Colt Officers 38 I had the cone recut on. Lead would build on the face of the barrel and drag on the cylinder, didn't want to rotate. The new forcing cone fixed it, no changes to barrel leading or accuracy.
Tim
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I can remember years ago that change in FC angle was the prescription for better accuracy. But in that era it was mostly jacketed bullets.
You can see how the more gradual transition can be kind to the bullet. Maybe that's why some rifle shooters like to use a throating reamer in their rifle?
Tom
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I agree. Of course it all has to add up. Chamber mouth diameter. Forcing cone angle. Bullet diameter. Alloy. Pressure. Cylinder timing. Barrel/Cylinder gap. Chamber mouth/forcing cone alignment. And some luck sprinkled on top.
With rifle in hand, I confidently go forth into the darkness.
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Aaron,
Is it a hand powered tool? And is it a tool that works in multiple size chamberings?
I’d like to do it on a .38, .41 and .45, all S&W and blue steel.
Thanks!
Tom
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Tom, It turns by hand. The cutter will do 357-45 caliber. A smaller cutter will do 32 caliber. I ordered mine through Brownells. It was a cutting set with bushings, T handle, shaft, etc. I use 5w20 oil when cutting. SLOW is the name of the game with a light pull on the shaft. You have to let the tool cut gently without force. Man will it cut. Then the cone is lapped with 600 grit compound to polish it. Look for the whole kit.
With rifle in hand, I confidently go forth into the darkness.
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Here is the kit. https://www.brownells.com/tools-cleaning/bore-barrel-tools/gun-barrel-tools/11-degree-.38-.45-intermediate-chamfering-kit/
You also need caliber specific bushings for the shaft for each caliber. You need 600 grit lapping compound.
It’s best to give them a call and get the whole mess at once. Looks like the kit is not in stock right now. I would call them.
With rifle in hand, I confidently go forth into the darkness.
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I bought the whole kit in the 1980's and set up a gun shows. Must have done about 100 or so. I used commercial cutting oil and it did a nice job. What I saw on my revolvers was better accuracy with ones that didn't line up perfectly. Also used it to cut the crowns on rebarreling jobs before the 90* cut on the front.
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I totally agree with your statement, about all things add up. A fix for one will not necessarily solve the same problem on others.
Mashburn
David a. Cogburn
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