cutting a cone for a Panda action

[Hal]

I'm chamber up a fire forming barrel for my Panda action.

What is the best way to cut the cone in the back of the barrel for the bolt nose clearance. How is this measured?

How much clearance between the bolt nose and the barrel?


Thanks for the help.

Hal

 

[Mike Bryant]

I'm chamber up a fire forming barrel for my Panda action.

What is the best way to cut the cone in the back of the barrel for the bolt nose clearance. How is this measured?

How much clearance between the bolt nose and the barrel?


Thanks for the help.

Hal

I turn my compound to where it's 29.5 degrees off of perpendicular to the lathe bed. 29.5 degrees instead of 30 degrees gives more clearance as you go out from the chamber. This is for a Panda bolt with 30 degree cone. For a Bat with 25 degree cone, I'll set the compound at 24.5 degrees off of perpendicular. I then use a Kennametal 1/4" F series boring bar with triangle tip to cut the cone. Here's a photo of a tool that I use to measure an old barrel and transfer the cone measurement to a new barrel. I personally haven't seen any need for the reamers that cut the 30 degree cones in the bore that have a pilot that runs in the bore of the barrel. With the 30 degree reamers, you have to cut the cone before you chamber the barrel. I cut the cone after I have most of the barrel chambered. I use that F series boring bar for a lot of cutting from roughing out chambers, to cutting cones, to cutting Remington counterbores to cutting crowns. You asked for the best method. Whether it's the best method or not, it's just a method. Not sure that there is a best method, just what works for whoever is doing it. The indicator shown in the photo is a 1" travel dial indicator. The cone on the indicator tightens down against the indicator stem with a set screw with a piece of weed eater cord beneath the set screw. The cone inside the device is cut at 30 degrees to mimic a 30 degree coned bolt. I cut my cones for no more than .010" clearance. If I was cutting them for the old Sako .220 Russian brass with balloon heads, I'd cut them for .005" clearance or less.

 

[CharlieH]

I'm no gunsmith, but I use the same method that Mike uses. I do it a little different in that I have my cone measuring tool as a separate part, it has a stem that goes into the bore to square up face of the tool in relation to the bore and the dial indicator pushes against it.
Charlie

 

[skeetlee]

I copied Mikes idea and it works flawless!! Id be lost without this tool. I check headspace with mine as well. Lee

 

[martin zuck]

This process is quite simple an I believe this is the way Kelbly does it. The panda shank is 1.115 so set your compound to 30 degrees . Touch the tool to the chamber edge and as you are feeding out with your compound move your saddle in .135. This will give you .007-.010 of clearance between bolt and barrel. I use a simple magnetic base indicator on the ways to move the saddle in the .135.

 

[Greg Walley]

Use a gage ball

I'm chamber up a fire forming barrel for my Panda action.

What is the best way to cut the cone in the back of the barrel for the bolt nose clearance. How is this measured?

How much clearance between the bolt nose and the barrel?


Thanks for the help.

Hal

Do you have a DRO on your lathe? Use this as a poor mans coordinate measuing machine. Put a square tool in the tool holder and set it about 1/2° proud of square and touch off on the shoulder and zero your 'X' axis. Make sure the tool is on center. You are going to use this tool like an "anvil" of a micrometer or a "jaw" of a caliper. You could also use a travel indicator and work from zero if you don't trust your measuring pressure and feel touching off with the massive lathe carriage assembly.

Measure the OD of the threads and touch the front edge of the tool to the top of the threads using a thin piece of paper for a feeler shim, then zero your 'Y' axis.

Place a 1.000" gage ball in the cone and measure from the shoulder to the top edge of the ball. To do this, move your "Y' axis in exactly 1/2 of the distance of the measured OD of the threads. This insures that you will be measuring the exact center of the ball.

The distance from the shoulder to the center edge of the gage ball for a PPC boltface should measure 1.928-1.930" for 0.008-0.010" clearance. It should measure 1.921" for a 308 boltface.

See the attached file for a CAD drawing of the dimensions.

This method is also convenient for measuring headspace.

Best regards,
Greg Walley
Kelbly's Inc.

 

[mwezell]

If the action is in hand you can simply cut the cone with the tenon left long, then screw the action on with the bolt in it...measure the gap between the shoulder and action face. Then take the appropiate amount off of the cone to set gap between bolt and barrel.

 

[Hal]

Thanks for the replies.
My lathe doesn't have DRO.
I'll work on my barreling project this weedend.

Hal

 

[martin zuck]

My apologies to Greg. He sure as hell ought know how it's done at Kelbly's! My method works for me in my low tech shop. Thru the years I've learned to keep things as simple as I can.

Martin

 

[Greg Walley]

My apologies to Greg. He sure as hell ought know how it's done at Kelbly's! My method works for me in my low tech shop. Thru the years I've learned to keep things as simple as I can.

Martin

No apology necessary Martin...that is a good way to do it. The method I provided is simply a convenient way to measure the finished tenon. Obviously, a DRO isn't absolutely necessary either. One can use travel indicators on the carriage to do the measuring. I'm sure most hobby gunsmiths don't have a DRO on their "Heavy 10"

Greg Walley
Kelbly's Inc.