Mauser Rebarrel - Part 2, Chambering

[Clemson]

Chambering the .257 Roberts barrel is straight-forward. It is done the same way for either a flat-breeched barrel or a safety-breeched barrel. Again, it is not my intent to show the "Best" way or the "Only" way. I chamber in the steady rest for several reasons: I don't have the measuring equipment to do a good enough job of centering the barrel in the 4-jaw chuck. I do have enough bed length on my lathe to do the work in the steady -- some folks don't. My bed is 40 inches beteen centers. That leaves enough room for the barrel, the tailstock, and the reamer. Finally, this is the way that I learned to chamber. I duplicated Jerry Kuhnhausen's setup for the first barrel that I ever chambered, and it has worked just fine for me over the years. For a hunting gun, I hardly see how you could do it any better.

 

We start with the muzzle in a chuck or collet. I actually use a 5C collet that I cut on a taper to match the barrel taper. You can purchase "emergency" collets that allow you to bore them out as you wish, and that is how I got a tapered collet. I set up the breech end in the Steady Rest. This shot shows me feeding a reamer into the breech. You have to hold the reamer some way. I am using a lathe dog. You can use a small wrench. John Hinnant shows how to make a wrench in his book. I can't see much advantage over the lathe dog. You want something that you can turn loose if the reamer grabs. It needs to be short enough to swing around without hitting anything and snapping off the reamer.

 

The procedure is pretty simple: Oil the reamer and the hole (I am using Ridgid Nuclear cutting oil), cut some, driving the reamer into the breech with the tailstock ram. Withdraw the reamer, brush off chips, and blow out the chamber with compressed air if you have it, then measure the depth and cut some more. I am driving the barrel in back gear at a slow speed. My South Bend has a slow spindle speed of 40 rpm, and that is what I use for reaming.

 

To measure progress, insert the "Go" gauge into the chamber. Measure with a depth mic the distance from the "Go" to the secondary torque shoulder. Compare this distance to what you measured on the action as the distance to the bolt face from the front of the action. I stopped reaming when I was a few thousandths from full depth (actually made about four cuts to remove about 0.1" of steel. I got lucky and did not over-cut, but be aware that those last few thousandths go fast!).

 

Before I removed the barrel from the lathe, I took a hand-held deburring tool and cut a chamfer on the chamber edge. It is very slight, less than 1/64 inch, but it makes all the difference in the world in feeding, and most factories don't take the time to do this step:

 

Finally, oil a bit of emery paper and run it against that new chamfer to smooth it out that last little bit:

 

The final chamber will be cut by hand in the next step.

 

Clemson

[Clark]

I don't push on chamber reamers with the live center.

I push with a Morse taper to Jacobs taper arbor that I have bought and faced for this purpose.

 

They cost $4 here, but are often on sale:

http://www.use-enco.com/CGI/INPDFF?PMPAGE=346

 

 

I should correct myself, and say, I don't do that for rifles.

With pistols, I don't care. I even put pistol reamers in the tailstock chuck.

[ken98k]

I don't push on chamber reamers with the live center.

I push with a Morse taper to Jacobs taper arbor that I have bought and faced for this purpose.

 

They cost $4 here, but are often on sale:

http://www.use-enco.com/CGI/INPDFF?PMPAGE=346

I should correct myself, and say, I don't do that for rifles.

With pistols, I don't care. I even put pistol reamers in the tailstock chuck.

 

Why do you use a JT instead of a live center?

Kenny

[z1r]

It is like this reamer holder:

 

http://www.midwayusa.com/mediasvr.dll/high...leitemid=542929

 

I've used it and it is ok, pretty good really but can be grabby. I use a commercial floating reamer holder that allows for axial as well angular alignment. Most only compensate for one or the other.

[Clemson]

I would probably use a floating reamer holder if I had one. Since I don't, I take a few precautions:

 

1. I cut a test bar on my lathe. It is about 30 inches long. I set up the bar between centers, then I take a cut on each end for about two inches. Measure each end with a micrometer. This tells me whether my lathe tailstock is aligned with the headstock. If the machine is cutting taper at all, I have to adjust the tailstock to compensate. This procedure would be even more crucial if I were offsetting the tailstock to cut tapers. My lathe has a taper attachment that I use to cut tapers, so once I dialed in the tailstock, I have not had to move it often.

 

2. Any reamer can grab if it is fed too fast. Note that I hold the reamer with a lathe dog. I could also use any wrench that is shorter than the lathe "swing." The important thing is to be able to let go of the dog (wrench, etc.) if the reamer grabs so that you don't snap the reamer off in the chamber.

 

The tailstock of this lathe is an MT3, and Clark's tool would work fine in it. I may just have to try it in the future if it offers an advantage. I have been happy with the live center method for my own purposes.

 

z1r: What brand of floating reamer holder are you using? I understand that some are to be preferred over others. Do you know what the advantages/disadvantages of the various brands may be?

 

Clemson

[Clark]

I dial in both ends of the barrel and put the breech swiveling in a gimbal of a single wire wrap in the 4 jaw, but I worry that the barrel is is flexed and not parallel with the lathe. That is why I push with something that provides axial force but not radial alignment.

 

I am sure there are alot of ways to do it, but like glass bedding, handloading, scope mounting, etc. when we each get our own system tuned up and working, it seems like the only way.

 

The first barrel we chambered in 2000, took the two machinists and I all night.

7 years later in my own shop,I cut threads and chambers like I am cleaning fish. It is a conditioned response.

I have a system.

As soon as a rifle gets a .5" 5 shot group at 100 yards, the chambering process was good enough for me, now to produce them faster.

[Clemson]

Clark,

 

That is an interesting barrel contour. Right where the steady is set up, there appears to be a raised ring. I assume that you will cut a dovetail for a rear sight in that ring, correct?

 

Clemson

[Clark]

Clark,

 

That is an interesting barrel contour. Right where the steady is set up, there appears to be a raised ring. I assume that you will cut a dovetail for a rear sight in that ring, correct?

 

Clemson

 

Correct.

 

 

That is a Rem700 30-06 take off barrel from Ebay that I was re chambering to 30 Mauser [7.62x25mm] to be put on a 1903 Turk.

 

I have bought dozens of old take off barrels off ebay.

 

The barrel was too short to fit through the headstock, so I had it in the steady rest.

 

That was a 6" at 50 yards boondoggle project:(

 

Today I ordered a .272" neck 6mmBR reamer from Pacific tool and gauge.

I have 5 benchrest take off 6mmPPC barrels and THIS TIME I am going to make a tackdriver.

It could happen.

 

[sonic1]

30 Mauser tell use more...how are you feeding the round ?

[680guy]

Correct.

That is a Rem700 30-06 take off barrel from Ebay that I was re chambering to 30 Mauser [7.62x25mm] to be put on a 1903 Turk.

 

I have bought dozens of old take off barrels off ebay.

 

The barrel was too short to fit through the headstock, so I had it in the steady rest.

 

That was a 6" at 50 yards boondoggle project:(

 

Today I ordered a .272" neck 6mmBR reamer from Pacific tool and gauge.

I have 5 benchrest take off 6mmPPC barrels and THIS TIME I am going to make a tackdriver.

It could happen.

Clark, I'd bet that barrel came off a 721 Rem. same theads as a 700 but that's how the sights were attached on on the 721. It's just an early version of the 700. If that barrel is as good as the two I've seen (I own one of them ) you got a real good shooter.

[Clark]

The 85 gr Factory S&B ammo is nearly all I have tried.

I may have exagerated how bad it is.

Here are my range notes:

 

 

First trip

 

 

1) I started out with some new S&B Tokarev ammo, with oil still in the

bore, with a 40X scope, the best I did was 1.2" 3 shot group at 100 yards.

 

2) At the end of 165 rounds fired in two hours [half the rate of

squirrel shooting]but the accuracy went down to a 4" 13 shot group at

50 yards,

 

Second trip

1) 30 Mauser rifle with M8-4x Leupold scope, S&B ammo and then Polish

surplus ammo.

a) S&B ammo 1.3" 5 shot group at 50 yards, 2.33" 5 shot group at 100

yards [could barely see the target with 4x scope]

Polish 1955 surplus ammo 4.8" 19 shot group at 50 yards

 

I should go to the range again and try longer bullets.

[Clark]

I went to see Randy Ketchum of Lynwood Guns [a real gunsmith] today to get the last of my chopped VZ24 parts.

 

He had seen this thread and had some criticism for me.

 

He said that every bore is bent.

Every bore has a spine.

You make a spud [he does it with a tool post grinder], .0002" smaller than the bore.

You dial in the breach.

You adjust the muzzle spider, possibly off center, so that the spud is dialed in at more than one distance from the breech.

Then the chamber is cut.

That way the chamber is cut concentric to the part of the bore just in front of the chamber.

The muzzle may be whirling around catywumpas, but that does not matter.

[Clemson]

Yep, the controversy over chambering in the headstock vs. chambering in the steady rest won't be settled here, that's for sure.

 

I stick by my opening paragraph above:

 

....it is not my intent to show the "Best" way or the "Only" way. I chamber in the steady rest for several reasons: I don't have the measuring equipment to do a good enough job of centering the barrel in the 4-jaw chuck. I do have enough bed length on my lathe to do the work in the steady -- some folks don't. My bed is 40 inches beteen centers. That leaves enough room for the barrel, the tailstock, and the reamer. Finally, this is the way that I learned to chamber. I duplicated Jerry Kuhnhausen's setup for the first barrel that I ever chambered, and it has worked just fine for me over the years. For a hunting gun, I hardly see how you could do it any better.

 

I assure you that there are many "real gunsmiths" who use the steady rest method. It probably makes a difference whether you are working on short-chambered barrels or barrels without pre-cut chambers. A barrel without a chamber gives ample room to insert a stud to measure off the lands. The pre-cut chamber requires you to follow the existing chamber, simply deepening it to get the correct headspace. A reamer will follow a hole -- it is nearly impossible to cut an eccentric hole with a reamer when you are using a steady to hold the barrel. You might succeed in cutting a chamber that is sloppier (Is that a word?) at the rear than at the throat.

 

In the final analysis, the proof is in the pudding. If the barrel shoots as you want it to, you are in good shape. If not, you may wish you had gone another direction. I doubt that the method of chambering will ever show up as a significant benefit or detriment to a hunting rifle.

 

Clemson

[z1r]

The proof as they say is in the pudding. I have chambered in various ways. Often due to necessity. As long as the results are good & consistent then I don;t think it matters.