Gene Beggs
Active member
This subject has been covered many times in depth here on the forum. I can't add much to what has already been said, but I've developed a trick or two of my own that I would like to share with you. After a comment I made yesterday, several asked me to describe my method of chambering, so here goes FWIW. 
There are basically two methods of chambering:
1. Thru the headstock.
2. In the steady rest.
Some insist the thru-the-headstock method is the only way, while others, myself included, feel the steady rest method is every bit as good. The truth is, everyone has their own way of doing things. I have used both methods and am comfortable with either but prefer the steady rest. Regardless of how it's done, what really matters is how the rifle shoots and handles.
My lathe is a JET 13x40 gear-head. I bought it new in '02 and have been fairly happy with it although, I wish I had spent twice the money and got a better quality machine. With the constant starting and stopping involved in barrel work, my original motor didn't last long. I replaced it with a WEG and have had no more trouble. If I were to buy a new lathe today, I would choose one made in Taiwan.
For the most part, I use a Bison six-inch, six-jaw, adjust-tru chuck and occassionaly an eight-inch four jaw. Reamers are JGS and PTG.
Many questions have been asked lately about chamber runout and how to prevent it. I'll tell you how I do it.
Let's fit up and chamber a barrel using the steady rest method. We will use a Kelbly/Stolle Panda action with a PPC bolt face. The barrel is a new cut-rifled 6mm 13.5 twist LV with a .237 bore.
Before we begin, be sure the lathe is level, the set-tru chuck dialed in and the tailstock spindle centered.
Run a patch thru the barrel to be sure it's clean. This is the time to determine which reamer pilot to use. I believe most will agree, you should select a pilot .0002 smaller than the one that won't go. I use a PTG range rod to try the pilot. For the .237 bore, I have found a .2369 pilot fits perfectly.
The rifle will be chambered in 6mm Beggs with a .269 neck. Since it will be a Sporter, we will finish the barrel at 22" measured from bolt face to crown.
We will use only about 2.500 inches of the straight, untapered portion of the barrel at the chamber end so let's cut off the excess in the bandsaw.
Place the breech end of the barrel in the chuck and tighten lightly; we will tighten securely later.
Place the live center in the muzzle and secure the tailstock. Keep the extension of the tailstock spindle as short as possible for added rigidity.
Grasp the barrel in the middle and press back firmly against the live center as you loosen the chuck and rotate the barrel slightly in the chuck jaws before tightening. Check the tension on the live center; it should be firm but not too tight. Lock the tailstock spindle.
Turn the forward two inches of the muzzle just enough to clean it up which insures this journal is true and concentric with the bore. I like to use a freshly sharpened HSS tool for this taking light cuts to minimize push off.
Chuck the chamber end of the barrel with about one inch protruding and face the ragged surface left by the bandsaw. With a sixty degree, piloted center drill, put a fresh center in the chamber end of the bore.
Place the muzzle in the chuck leaving about .750 of the previously turned journal exposed and the chamber end of the barrel supported in the live center. Grasp the barrel in the middle and press back firmly against the live center, loosen the chuck slightly and rotate the barrel in the chuck to be sure it's not in a bind and tighten the chuck. With a dial indicator resting on the .750 length of the muzzle, make final adjustments to the set-tru chuck to get the muzzle running true. The barrel will not be removed from the chuck until the chamber and tenon are finished.
Using a freshly sharpened HSS tool, take light cuts and just barely true up the aft end of the barrel for about .750 or so. We will run the steady rest on this area while chambering, which we will do next. What? You mean you are not going to complete the tenon and thread before reaming the chamber? Nope! This is where I deviate from the norm. We will ream the chamber to about 85 or ninety percent depth before we do the tenon.
Regardless of whether you are chambering thru the headstock or in the steady rest, the reamer follows the bore; how could it do otherwise? If the bore wanders off a bit the nose of the reamer follows and the back end is deflected in the opposite direction. This is where the runout comes from. When the chamber is cut to about ninety percent depth, it is not unusual for the aft end to be running out .003 to .004 TIR, sometimes as much as .005 or .006. Don't be alarmed; this is all well and good and will be compensated for when the tenon is turned and threaded.
With the chamber almost finished we will now turn the tenon to final diameter (1.062) and thread 18 TPI. Remember that the muzzle end of the barrel is left undisturbed in the chuck until the tenon and chamber are finished.
I thread and chamber at 60 rpm. I cut straight in on the threads rather than using the 29 degree cut with the compound. Since I don't do this for a living, I take my time with the threads starting out with .010 to .015 depth of cut for the first two or three passes. Of course, with most lathe crossfeeds this means the actual depth of cut is half that. As the threads get deeper, I take progressively smaller cuts, the last three or four passes being only .001 at a time and I chase the last two or three passes to eliminate pushoff. I use a thread mike and rarely have to make more than two trial fits to get the fit just right. Once the threads are cut to final depth, I take a light skim cut off the tops to smooth and even them out before polishing with 320 grit and a Cratex stick. Time to cut the 30 degree cone.
Put the live center in the tenon and place the steady rest so it runs on top of the threads. Adjust and secure the steady rest fingers and then slide the tailstock out of the way. Oh, BTW, I lube the tenon well with a fifty-fifty mixture of motor oil and STP. Works good!
Set the compound to 30 degrees and with a small boring bore cutting from the bore out, take a few cuts but leave the cone short of final depth. We will see how much further we need to cut by making a trial fit in the receiver.
Remove the firing pin assembly, spray the bolt face with brake cleaner and dry with compressed air. You'll find out why in a minute.
Screw the action onto the threads but not all the way. Place the stripped bolt into the receiver and snug the action up by hand so the bolt nose presses against the cone. Measure the gap between the tenon shoulder and receiver face with a thickness gauge. That measurement plus .007 is the amount that must be cut off the cone. Once the cut is made, take a small length of lead squirt obtained from your buddy that makes bullets and tape it to the bolt face with a small piece of masking tape and lap it over the bolt nose. After the action is snugged up hand tight on the tenon, insert and close the bolt which will squeeze the lead squirt between the cone and bolt nose. Measure this flattened lead squirt with a dial caliper to get the distance between the cone and bolt nose. Some prefer only .005 here, others will accept .010 to .015. I shoot for .007 but am happy with .010.
Once the tenon and cone are finished, it's time to finish the chamber. Place the 'GO' gauge in the chamber, screw the action onto the threads with the bolt closed and snug it up against the gauge. If you have done everything right up to this point, you will have somewhere around a .050 to .060 gap between the tenon shoulder and face of the receiver. Measure this gap with a thickness gauge. That is how much deeper the reamer must be run to finish the chamber. I usually cut about .002 more to compensate for crush when the barrel is torqued up tight with the action wrench.
Well guys, that's about all I know about it. Hope this helps. If you have any questions we can discuss them in the posts below.
Adios for now
Gene Beggs
There are basically two methods of chambering:
1. Thru the headstock.
2. In the steady rest.
Some insist the thru-the-headstock method is the only way, while others, myself included, feel the steady rest method is every bit as good. The truth is, everyone has their own way of doing things. I have used both methods and am comfortable with either but prefer the steady rest. Regardless of how it's done, what really matters is how the rifle shoots and handles.
My lathe is a JET 13x40 gear-head. I bought it new in '02 and have been fairly happy with it although, I wish I had spent twice the money and got a better quality machine. With the constant starting and stopping involved in barrel work, my original motor didn't last long. I replaced it with a WEG and have had no more trouble. If I were to buy a new lathe today, I would choose one made in Taiwan.
For the most part, I use a Bison six-inch, six-jaw, adjust-tru chuck and occassionaly an eight-inch four jaw. Reamers are JGS and PTG.
Many questions have been asked lately about chamber runout and how to prevent it. I'll tell you how I do it.
Let's fit up and chamber a barrel using the steady rest method. We will use a Kelbly/Stolle Panda action with a PPC bolt face. The barrel is a new cut-rifled 6mm 13.5 twist LV with a .237 bore.
Before we begin, be sure the lathe is level, the set-tru chuck dialed in and the tailstock spindle centered.
Run a patch thru the barrel to be sure it's clean. This is the time to determine which reamer pilot to use. I believe most will agree, you should select a pilot .0002 smaller than the one that won't go. I use a PTG range rod to try the pilot. For the .237 bore, I have found a .2369 pilot fits perfectly.
The rifle will be chambered in 6mm Beggs with a .269 neck. Since it will be a Sporter, we will finish the barrel at 22" measured from bolt face to crown.
We will use only about 2.500 inches of the straight, untapered portion of the barrel at the chamber end so let's cut off the excess in the bandsaw.
Place the breech end of the barrel in the chuck and tighten lightly; we will tighten securely later.
Place the live center in the muzzle and secure the tailstock. Keep the extension of the tailstock spindle as short as possible for added rigidity.
Grasp the barrel in the middle and press back firmly against the live center as you loosen the chuck and rotate the barrel slightly in the chuck jaws before tightening. Check the tension on the live center; it should be firm but not too tight. Lock the tailstock spindle.
Turn the forward two inches of the muzzle just enough to clean it up which insures this journal is true and concentric with the bore. I like to use a freshly sharpened HSS tool for this taking light cuts to minimize push off.
Chuck the chamber end of the barrel with about one inch protruding and face the ragged surface left by the bandsaw. With a sixty degree, piloted center drill, put a fresh center in the chamber end of the bore.
Place the muzzle in the chuck leaving about .750 of the previously turned journal exposed and the chamber end of the barrel supported in the live center. Grasp the barrel in the middle and press back firmly against the live center, loosen the chuck slightly and rotate the barrel in the chuck to be sure it's not in a bind and tighten the chuck. With a dial indicator resting on the .750 length of the muzzle, make final adjustments to the set-tru chuck to get the muzzle running true. The barrel will not be removed from the chuck until the chamber and tenon are finished.
Using a freshly sharpened HSS tool, take light cuts and just barely true up the aft end of the barrel for about .750 or so. We will run the steady rest on this area while chambering, which we will do next. What?
You mean you are not going to complete the tenon and thread before reaming the chamber? Nope! This is where I deviate from the norm. We will ream the chamber to about 85 or ninety percent depth before we do the tenon.Regardless of whether you are chambering thru the headstock or in the steady rest, the reamer follows the bore; how could it do otherwise? If the bore wanders off a bit the nose of the reamer follows and the back end is deflected in the opposite direction. This is where the runout comes from. When the chamber is cut to about ninety percent depth, it is not unusual for the aft end to be running out .003 to .004 TIR, sometimes as much as .005 or .006. Don't be alarmed; this is all well and good and will be compensated for when the tenon is turned and threaded.
With the chamber almost finished we will now turn the tenon to final diameter (1.062) and thread 18 TPI. Remember that the muzzle end of the barrel is left undisturbed in the chuck until the tenon and chamber are finished.
I thread and chamber at 60 rpm. I cut straight in on the threads rather than using the 29 degree cut with the compound. Since I don't do this for a living, I take my time with the threads starting out with .010 to .015 depth of cut for the first two or three passes. Of course, with most lathe crossfeeds this means the actual depth of cut is half that. As the threads get deeper, I take progressively smaller cuts, the last three or four passes being only .001 at a time and I chase the last two or three passes to eliminate pushoff. I use a thread mike and rarely have to make more than two trial fits to get the fit just right. Once the threads are cut to final depth, I take a light skim cut off the tops to smooth and even them out before polishing with 320 grit and a Cratex stick. Time to cut the 30 degree cone.
Put the live center in the tenon and place the steady rest so it runs on top of the threads. Adjust and secure the steady rest fingers and then slide the tailstock out of the way. Oh, BTW, I lube the tenon well with a fifty-fifty mixture of motor oil and STP. Works good!
Set the compound to 30 degrees and with a small boring bore cutting from the bore out, take a few cuts but leave the cone short of final depth. We will see how much further we need to cut by making a trial fit in the receiver.
Remove the firing pin assembly, spray the bolt face with brake cleaner and dry with compressed air. You'll find out why in a minute.
Screw the action onto the threads but not all the way. Place the stripped bolt into the receiver and snug the action up by hand so the bolt nose presses against the cone. Measure the gap between the tenon shoulder and receiver face with a thickness gauge. That measurement plus .007 is the amount that must be cut off the cone. Once the cut is made, take a small length of lead squirt obtained from your buddy that makes bullets and tape it to the bolt face with a small piece of masking tape and lap it over the bolt nose. After the action is snugged up hand tight on the tenon, insert and close the bolt which will squeeze the lead squirt between the cone and bolt nose. Measure this flattened lead squirt with a dial caliper to get the distance between the cone and bolt nose. Some prefer only .005 here, others will accept .010 to .015. I shoot for .007 but am happy with .010.
Once the tenon and cone are finished, it's time to finish the chamber. Place the 'GO' gauge in the chamber, screw the action onto the threads with the bolt closed and snug it up against the gauge. If you have done everything right up to this point, you will have somewhere around a .050 to .060 gap between the tenon shoulder and face of the receiver. Measure this gap with a thickness gauge. That is how much deeper the reamer must be run to finish the chamber. I usually cut about .002 more to compensate for crush when the barrel is torqued up tight with the action wrench.
Well guys, that's about all I know about it. Hope this helps. If you have any questions we can discuss them in the posts below.
Adios for now
Gene Beggs
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