Canneluring Bullets; Bullet Diameter Changes

[Blackhawker]

I recently purchased a bullet canneluring tool made by C-H.  As there are many loading applications in which this tool can be useful, my main reason for purchasing it is to cannelure Hornady 180 grain XTP bullets for my "Ruger and T/C only" 38-40 loads.  I spent a little time yesterday canneluring some cast 180 grain bullets and had noticed that the area just above and below the formed cannelure tends to "bulge" a bit.  In fact, I measured the bulge as compared to the rest of the bearing surface of the bullet.  What was once .402 inches becomes .403 to .404 inches.  I tried the same with a Berry's copper plated bullet and found the same to occur with a bulge of .001 to .002 inches to develop just above and below the formed cannelure.  It only makes sense that this would occur; the bullet mass must move or flow somewhere.  Where a depression is made, an adjacent bulge should develop.  I wondered if this phenomenon can be found with factory bullets so I measured some of my Hornady bullets which have cannelures in them and found no such bulge, at least not more than perhaps .0005".  I wonder if factory bullets are resized after canneluring?  I would think that the cannelures would become disfigured after being resized. 

I wonder if the use of a cannelure tool is effective or should be used if bullets tend to bulge as I have described, especially when loading heavy sided loads through revolver throats that are at the same diameter or even .001 inches smaller than the newly formed bulge?  I sure would hate to develop excessively high and/or dangerous pressures by putting cannelures in bullets.

Has anyone else here used a cannelure tool and found this to occur on your bullets?

[shot1]

I have not used the canneluring tool but I feel your pain. I loaded up some ammo for my brother-n- law  for a Winchester rifle and a Colt DA revolver he has in 38-40. I could not find a jacketed bullet with a cannelure. I tried to use some smooth sided bullets for the 40 cal autos but could not get enough neck tension to hold the bullet in place. I bought some Shooters Choice 180 gr .401 cast bullets made just for the 38-40 that had the cannelure in the correct place and they worked through the rifle as slick as a ribbon but they would not even chamber in the Colt pistol because it made the neck of the cartridge too large a diameter. The cast bullets were .401 and the factory Rem ammo he had with jacket bullets had .400 diameter bullets. I used 6.2 grs Unique and it was very accurate in the rifle.  You might try a Lee bullet sizing die to try to bet everything back to size. They size from the nose back toward the base because you push them through nose first. I should leave you enough cannelure to get a crimp on. You will never know until you try it.

[nicholst55]

Blackhawker:  just my personal feelings here; no experience (yet) with the cannelure tool.  I do understand what you experienced to be a common occurrence, though.  My feeling is that unless you're running your loads on the very ragged edge of safety already, then having a small area on either side of the cannelure enlarged by .001-002" probably isn't going to hurt anything.  The enlarged area will be swaged down to groove diameter once it gets into the bore anyway.  Unless you're shooting bullets a whole lot harder than Linotype, I personally wouldn't lose any sleep over it.

To be on the safe side, download a few rounds and test fire them.  If no issues present themselves, work back up to your original load while observing carefully for pressure signs.  Use your chronograph if you have one to give you an indication on what's going on.

I bet you'll be just fine.

[Blackhawker]

Nicholst55, what you wrote is sort of what I was wondering for myself.  The area that has enlarged is roughly only 25% of the bearring surface of the bullet and I'd bet it would be swaged back down easily upon firing.  The bullets I'm using are of BNH 15.  I was going to try a few lighter loads (on the light side of my heavy loads) and see what happens, should the rounds chamber correctly. 

[wncchester]

I haven't used that tool but experiments by P.O. Ackley in the 50s indicates that such small diameter changes in bullets will have virtually no increased pressure effect when fired.

[Blackhawker]

I haven't used that tool but experiments by P.O. Ackley in the 50s indicates that such small diameter changes in bullets will have virtually no increased pressure effect when fired.

Good to know....thank you!

[HL]

I use that exact same tool to cannelure all of my 458 bullets I use in my 1895. I have not noticed any change in bullet impact or accuracy after putting a cannelure on those. I will have to mic those to see what you are talking about. I really didn't think about checking before and after canneluring.

HL

[LONGTOM]

I used the same tool on some Winchester .451 230gr RNHPs to try in my Blackhawk and if anything, the slight bulges seemed to help.
Kind of like lead bullets bumping up in diameter when fired.
My groups tightened up a lot compaired to what they were with the same bullet before the cannelure.



LONGTOM

[Blackhawker]

I used the same tool on some Winchester .451 230gr RNHPs to try in my Blackhawk and if anything, the slight bulges seemed to help.
Kind of like lead bullets bumping up in diameter when fired.
My groups tightened up a lot compaired to what they were with the same bullet before the cannelure.

LONGTOM

I can see how that would help on a .451 bullet in a .452 chamber.  In fact, I was thinking of canneluring some 225 g Hornady XTP's for my .454 Casull.
My biggest concern here however is that the bullets I have cannelured are already at or near the throat diameter of my revolver.  Additionally, I'm running rather high pressure loads through them and I am just being cautious about not running oversized bullets through the cylinder throats when I'm already running at higher pressures. 
I guess I'll find out in the next few day what happens as I'm planning on taking it out to the range soon.  I'll report back my observations on accuracy and pressure signs.