Cylinder Chamfering

MISFIRE · April 11, 2006, 11:32 PM

The cylinder edges on my GP100 are sharp, I mean really sharp. Using HK speedloaders at Thunder Ranch was exasperating. The edges even catch on the jackets of Rainier FMJ's. I had a K-38 done here in LA. Nice job, but it took months and three, hour long trips ( not done on promise date/s) to get it back. Obviously I need a good reamer (e.g. Brownell's). Know of any other source? Any other special tools needed? I have a good drill press and chuck. Obviously I also a good set of instructions. Any recommendations, advice, comments would be appreciated. I had read somewhere a while back that the extractor should not be touched. The K-38 chamfering extends into about an 1/8" of the extractor leafs. I haven't had any cases slip off so far.

Dfariswheel · April 12, 2006, 01:25 AM

You chamfer chamber mouths BY HAND with the Brownell's piloted cutter, NOT in a drill press.

When chamfering, REMOVE the ejector assembly or it'll be ruined.

Chamfer the absolute MINIMUM you can get by with.
Over doing it reduces case head support and can ruin the cylinder.
All that's really needed is to just break the sharp edge.

To bevel the mouth, insert the pilot into the chamber, and turn and press with even, firm pressure.
You want to make a smooth, even cut without any scalloping caused by uneven pressure.
Don't use too much force, let the cutter do the work.

Try to cut all chambers to the same depth.

Don't get carried away.
It takes remarkably little bevel to do the job, and MOST people cut too way much the first time out.

If you didn't cut quite enough, you can cut a little more.
However, you can't put metal back if you cut too much.
QUITE while you're ahead.

mete · April 12, 2006, 04:27 AM

Yes , by hand ! I use a chamfering bit. 1/32" MAX.

Ruger4570 · April 16, 2006, 02:54 PM

The above is correct. You only want to remove the sharpness, not create a funnel. Breaking the edge off take only a slight amount of bevel.

MISFIRE · April 16, 2006, 04:28 PM

Thanks guys. Now I just need to pop for 100 bucks to Brownells. Don't know any other place for this kind of thing.

mete · April 16, 2006, 05:06 PM

$100 ?? no just buy a chamfering bit for a fraction of that.

MISFIRE · April 18, 2006, 02:16 PM

mete,
More details mete. What's the chamfering "bit" you are referring to? I have a whole bunch of drillmotor type chamfering bits. In a drillmotor they have a tendency to chatter. I could maybe use a tap wrench or an old drill chuck to turn one by hand but the bits do not have a pilot. The $100 to Brownells includes a brass, caliber specific, pilot.
My drill press has a Laser centering device. Contemplating chucking up the cylinder on my drill press, centering with the Laser, and turning the spindle by hand... Laser is not accurate enough. By damn I wonder if I could just center the bit on a cylinder in a loose chuck, tighten it down, and turn the spindle by hand? Sounds a bit tricky but, being retired, I've got the time and I enjoy metal work. Any "real" gunsmiths/machinists care to comment/dump on this notion? A new cylinder would probably set me back a bunch more than $100 ( old saying "Penny wise, pound foolish" comes to mind ) and maybe result in my GP100 not being as good (excellent) a shooter. Not good!

RsqVet · April 18, 2006, 03:11 PM

Hello ---

I thought about using non-gunsmith tooling as well to do mine but talked myself out of it --- look at what brownells sellls, the cutting angle is a los more shallow than anythng I found so it's going to take less metal off less quick and at a diffirent angle --- I can not see how I could duplicate this with most tooling I have seen from most sources which tends to make a funnel shape because that's what is required for the applications they are designed for, not to mention that cutting the cyliner is goign to be tough steel so I'd want new tooling --- I do a lot of shoping a used places -- there a cutter might be 20 bucks for a large one, if it's new it's gona be close to the brownells price for the right tool to beign with.

I also considered a shaped abrasive wheel however all the ones I saw in the shape you woudl want were pretty coarse and I'd be worried about taking too much in polishing it out --- like messing up feed ramp polish job.

Not saying you can't make it work somehow but chances of sub optimal or failure talked me out of it plus the cutter brownells sells works for mutiple calibers if you change out the piolt --- now any fool could make diffirent caliber pilots themself so that is whit I will liekly do when I get around to buying one to do my guns.

Ruger4570 · April 19, 2006, 12:55 PM

I am not sure this would work, but it works to crown a rifle barrel. If you can find an industrial rivet the right size, chuck it in a drill motor and use some fine lapping compound it would seem you can soften up the sharp edges enough. Just a shadetree gunsmiths thought.

chadwimc · April 19, 2006, 03:43 PM

I have indexed various parts on my mill/drill by clamping the piece down firmly. Then I use a piece of stock that is the same diameter of the work piece(You may have to make this). Insert the index piece in the drill. Run the table up, centering the piece to be worked on. Clamp everything in place. Run the table down, remove the index piece, insert the tool you want to use. It should be centered. A real machinest could probably explain this much better...

mete · April 19, 2006, 04:25 PM

Maybe I should use the word countersink. Under that name you will find them at places like www.mcmaster.com I have a 82 degree countersink from them that works fine , quick and easy ,by hand !

April 11, 2006, 11:32 PM	#1
MISFIRE Member Join Date: October 20, 2000 Location: Aliso Viejo, Ca Posts: 86	Cylinder Chamfering The cylinder edges on my GP100 are sharp, I mean really sharp. Using HK speedloaders at Thunder Ranch was exasperating. The edges even catch on the jackets of Rainier FMJ's. I had a K-38 done here in LA. Nice job, but it took months and three, hour long trips ( not done on promise date/s) to get it back. Obviously I need a good reamer (e.g. Brownell's). Know of any other source? Any other special tools needed? I have a good drill press and chuck. Obviously I also a good set of instructions. Any recommendations, advice, comments would be appreciated. I had read somewhere a while back that the extractor should not be touched. The K-38 chamfering extends into about an 1/8" of the extractor leafs. I haven't had any cases slip off so far. __________________ MISFIRE

April 16, 2006, 04:28 PM	#5
MISFIRE Member Join Date: October 20, 2000 Location: Aliso Viejo, Ca Posts: 86	Thanks guys. Now I just need to pop for 100 bucks to Brownells. Don't know any other place for this kind of thing. __________________ MISFIRE

April 18, 2006, 02:16 PM	#7
MISFIRE Member Join Date: October 20, 2000 Location: Aliso Viejo, Ca Posts: 86	mete, More details mete. What's the chamfering "bit" you are referring to? I have a whole bunch of drillmotor type chamfering bits. In a drillmotor they have a tendency to chatter. I could maybe use a tap wrench or an old drill chuck to turn one by hand but the bits do not have a pilot. The $100 to Brownells includes a brass, caliber specific, pilot. My drill press has a Laser centering device. Contemplating chucking up the cylinder on my drill press, centering with the Laser, and turning the spindle by hand... Laser is not accurate enough. By damn I wonder if I could just center the bit on a cylinder in a loose chuck, tighten it down, and turn the spindle by hand? Sounds a bit tricky but, being retired, I've got the time and I enjoy metal work. Any "real" gunsmiths/machinists care to comment/dump on this notion? A new cylinder would probably set me back a bunch more than $100 ( old saying "Penny wise, pound foolish" comes to mind ) and maybe result in my GP100 not being as good (excellent) a shooter. Not good! __________________ MISFIRE

April 12, 2006, 01:25 AM	#2
Dfariswheel Senior Member Join Date: May 4, 2001 Posts: 7,478	You chamfer chamber mouths BY HAND with the Brownell's piloted cutter, NOT in a drill press. When chamfering, REMOVE the ejector assembly or it'll be ruined. Chamfer the absolute MINIMUM you can get by with. Over doing it reduces case head support and can ruin the cylinder. All that's really needed is to just break the sharp edge. To bevel the mouth, insert the pilot into the chamber, and turn and press with even, firm pressure. You want to make a smooth, even cut without any scalloping caused by uneven pressure. Don't use too much force, let the cutter do the work. Try to cut all chambers to the same depth. Don't get carried away. It takes remarkably little bevel to do the job, and MOST people cut too way much the first time out. If you didn't cut quite enough, you can cut a little more. However, you can't put metal back if you cut too much. QUITE while you're ahead.

April 12, 2006, 04:27 AM	#3
mete Senior Member Join Date: June 14, 2004 Location: NY State Posts: 6,575	Yes , by hand ! I use a chamfering bit. 1/32" MAX.

April 16, 2006, 02:54 PM	#4
Ruger4570 Senior Member Join Date: April 3, 2005 Location: Rochester, New York Posts: 2,136	The above is correct. You only want to remove the sharpness, not create a funnel. Breaking the edge off take only a slight amount of bevel.

April 16, 2006, 05:06 PM	#6
mete Senior Member Join Date: June 14, 2004 Location: NY State Posts: 6,575	$100 ?? no just buy a chamfering bit for a fraction of that.

April 18, 2006, 03:11 PM	#8
RsqVet Senior Member Join Date: February 20, 2005 Posts: 2,474	Hello --- I thought about using non-gunsmith tooling as well to do mine but talked myself out of it --- look at what brownells sellls, the cutting angle is a los more shallow than anythng I found so it's going to take less metal off less quick and at a diffirent angle --- I can not see how I could duplicate this with most tooling I have seen from most sources which tends to make a funnel shape because that's what is required for the applications they are designed for, not to mention that cutting the cyliner is goign to be tough steel so I'd want new tooling --- I do a lot of shoping a used places -- there a cutter might be 20 bucks for a large one, if it's new it's gona be close to the brownells price for the right tool to beign with. I also considered a shaped abrasive wheel however all the ones I saw in the shape you woudl want were pretty coarse and I'd be worried about taking too much in polishing it out --- like messing up feed ramp polish job. Not saying you can't make it work somehow but chances of sub optimal or failure talked me out of it plus the cutter brownells sells works for mutiple calibers if you change out the piolt --- now any fool could make diffirent caliber pilots themself so that is whit I will liekly do when I get around to buying one to do my guns.

April 19, 2006, 12:55 PM	#9
Ruger4570 Senior Member Join Date: April 3, 2005 Location: Rochester, New York Posts: 2,136	I am not sure this would work, but it works to crown a rifle barrel. If you can find an industrial rivet the right size, chuck it in a drill motor and use some fine lapping compound it would seem you can soften up the sharp edges enough. Just a shadetree gunsmiths thought.

April 19, 2006, 03:43 PM	#10
chadwimc Senior Member Join Date: July 15, 2005 Posts: 155	I have indexed various parts on my mill/drill by clamping the piece down firmly. Then I use a piece of stock that is the same diameter of the work piece(You may have to make this). Insert the index piece in the drill. Run the table up, centering the piece to be worked on. Clamp everything in place. Run the table down, remove the index piece, insert the tool you want to use. It should be centered. A real machinest could probably explain this much better...

April 19, 2006, 04:25 PM	#11
mete Senior Member Join Date: June 14, 2004 Location: NY State Posts: 6,575	Maybe I should use the word countersink. Under that name you will find them at places like www.mcmaster.com I have a 82 degree countersink from them that works fine , quick and easy ,by hand !