# How about a barrel chambering thread?



## ScottD (Aug 15, 2018)

Here is a Bartlein Barrel.  6MM 4 groove Light Varmint contour.  I am going to chamber it for my Benchrest Rifle in 6PPC.  I thought maybe y'all would want to see how I do it.


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## ScottD (Aug 15, 2018)

I guess the first step is the Lathe.  It is a Summit 14x60.  It has low hours usage (really low) and I have a 3 Jaw adjustable chuck.  This is a little large compared to most gunsmith lathes but it works.  FYI - the three jaw adjustable chuck is a 3 jaw chuck that has an 4 jaw type adjustable base.


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## ScottD (Aug 15, 2018)

This is what a barrel blank looks like when you get it.  This one is about 28" long.  has about 5" of straight taper that is 1.200" diameter and the tapers to .875 on the small end.  I will leave about 2.750" of straight on the chamber end and will have a finished length of about 21.250" so that I can make my weight limit.

This Photo shows that this is a Bartlein 4 groove Stainless steel (416) with a 14 twist and a land/groove measurement of .237/.243.


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## ScottD (Aug 15, 2018)

So first I cut about 2-1/2" off the fat end and about 4" off the skinny end.  Nothing critical here. just cut with a band saw.


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## ScottD (Aug 15, 2018)

Now comes the not normal part for most chambering jobs.  You can see in the photos that I have aluminum sleeves at each end of the barrel.  These have been machined to match the taper of the barrel.  A couple of drops of super glue and then the are pressed onto the barrel.  With the taper they really lock down pretty well but I add the glue just for insurance that nothing moves.  The sleeves make it easier to chuck up the barrel as the barrel is tapered and it is like trying to chuck up on a long cone shape.





So now I chuck up on the sleeve on the chamber end of the barrel.  And I face the end.


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## ScottD (Aug 15, 2018)

Here is a video of the runnout of the bore vs the Outside diameter of the barrel.



https://imgur.com/MVkT2ix


The Muzzle run out was .003 TIR which is about normal.  The muzzle runout was .009 TIR which is a little much.  This is why you have to work off of the bore not the OD of the barrel.


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## ScottD (Aug 15, 2018)

So now we put the muzzle end in the chuck and adjust it until we have zero runout on the bore.  This video shows the Indicator checking the bore at zero.  You can see the lands and grooves at each reading but everything is within a few tenths.  This indicator the whole numbers are thousands of an inch and each mark is a ten-thousanths of an inch.


https://imgur.com/n6ntpXY


Once we get it adjusted to zero - meaning the bore is running concentric regardless of what the outside diameter is doing, we use a boring bar to cut a "center" using the lathe compound.  This insures the cut for the center is concentric to the bore.


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## ScottD (Aug 15, 2018)

Then we flip it over and do the same for the muzzle end.  Get it to run true, cut a center.

This is what it looks like when done.


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## ScottD (Aug 15, 2018)

So now we put the barrel between centers.  This means that a precision cone is put into each end of the barrel.  The tailstock holds a live center (free to spin) and the chuck holds a dead center with a drop of superglue so that there is enough grip that the barrel spins with that center thats in the chuck.  Now we have a BORE that is running concentric between the two centers.  It doesn't mean the bore is straight, just that the two ends are centered on its axis.

Now we take a light cut on both the sleeve ODs.

Once completed, the OD of the sleeves and the bore are now centered on the same axis.


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## ScottD (Aug 15, 2018)

That is it for today. Tomorrow cut the tenon, chamber, and thread.


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## hayseed_theology (Aug 15, 2018)

Very cool.  Thank you for sharing.


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## ScottD (Aug 16, 2018)

OK.  So now I have put the chamber end back into the adjustable chuck - chucking up on my trued sleeve.  I again put the indicator on the bore and get the bore running true.  Now that I have the bore at this end running "zero" I should also have the muzzle end running zero(or close to it) because the sleeve is aligned with the bore end to end.
Now I take a custom Drill Bit 24/64", which is just smaller than the chamber will be, and drill just short of the chamber length.  The drill has a point that matches the angle of the shoulder on the case.


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## ScottD (Aug 16, 2018)

This allows me to get the indicator all the way up the the throat of the chamber.





This is where i get the runout zeroed again.  This is where it really counts and needs to be ZERO.  The bore needs to be true. I try to get it within a couple of tenths (ten-thousands of an inch). I focus mostly on the lands since that is where the pilot bushing will contact.  This barrel thae lands vs grooves both trued together very well. So now the bore is aligned and running true center and I can start cutting metal. With this one set-up I will cut the chamber and the tenon and threads and shoulder so that everything is in alignment.
The first thing is to rough out the tenon.


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## ScottD (Aug 16, 2018)

You will see that all of the cutting tools are A R Warner which is popular with Gunsmiths.  They have high speed steel inserts which give a great finish on stainless steel even at relatively low speeds.

After roughing out the tenon I check my zero again just to make sure.....last chance.
Now I use a boring bar to take a light cut on the chamber.  This is to remove any chance that the drilled hole is off because a drill is not that rigid and tends to follow the existing hole.  Anyway - the boring bar cut will be straight with the throat and give the reamer a good straight start.  This rifle has a coned bolt so the very end of the chamber will be coned later.  This means I can cut the first .050" with the boring bar to finished dimension since it will be removed anyway.


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## ScottD (Aug 16, 2018)

Here is the reamer drawing. 6PPC .262 neck





The reamer has a pilot with a removable bushing.  I have a range of bushings each a tenth different in size.  Just test fit to find the size that is a good snug fit.






I test fit it in the stub I cut off.  In this case I used .2368 bushing.


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## ScottD (Aug 16, 2018)

Here is the reamer holder and reamer "pusher".  The pusher is just a round dome shaped rod.  It pushes against a hard flat plate in the reamer holder. There is plenty of room and this allows the reamer to "float" without influence or binding.





Ready to chamber.  The short T Handle is what you hold onto by hand to keep the Reamer from tuning while the barrel is spinning on it.  The reamer has a lot of surface area that it is cutting and requires a good bit of force to hold it.  But the handle is short enough that if it grabs, you just let go and let it spin with the barrel without damaging anything or anyone.


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## ScottD (Aug 16, 2018)

So now we chamber.  I chamber at 71 rpm's.  I like to use Rigid aerosol threading oil.  I have already cut most of the material so not much left to take out so I use lots of short firm cuts. Remove the reamer often and clean chips, re-spray oil and cut again.


https://imgur.com/8zXJ2C9


You can see in the video the point where the reamer starts cutting by how it jerks a little bit when it starts.


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## ScottD (Aug 16, 2018)

I keep reaming until my go-gauge will go in and be below flush about .020".  It is hard to ream to an exact depth, but you can ream a little too deep and then go back and face off the barrel to the correct depth and then also cut the shoulder.
Here is a blurry picture of the go-gauge.





and here it is below flush


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## ScottD (Aug 16, 2018)

Now we will cut the tenon to correct size (diameter). The manufacturer tell me the diameter should be 1.0625" and the shank length should be 1.115" (barrel shoulder to face) and that the threads should be 1-1/16-18tpi to a measurement of 1.0715 over .032 wires.
I want my chamber to be exactly .0015" deeper than my go-gauge.  Normally a gunsmith has both a go and a nogo gauge to work with and as long as one fits and the other doesn't, you are good to go.  I need a little more precision than that due to custom dies and such, so I work only with a go gauge and a predetermined chamber depth.

So I machine the tenon down to 1.0625.





and cut a thread relief at the barrel shoulder.




The thread relief is cut so that the threaded section runs out into the relief.  You will see why in a bit.


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## ScottD (Aug 16, 2018)

The tenon length is supposed to be 1.115" from the barrel shoulder to the barrel face, and I want my go gauge to be .0015" deeper than the face.  I have a Gauge that slips over the tenon that is 1.115 long.  So i can depth mic from this ring to the go gauge and I want to be at .0015"
I take a light cut on the shoulder of the barrel and then take a measurement and know how much more to cut off the shoulder.  I make that cut and then move 1.115 and face the barrel. That sets my headspace.





The bronze part is my tenon length gauge.


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## ScottD (Aug 16, 2018)

Now the most verve wrecking part.  Threading the tenon.  To make the threads we take a pointed threading tool and set the lathe to 18 threads per inch and the lathe will move the saddle at 18tpi as the barrel is turning.  This is done from the end of the barrel moving toward the shoulder of the barrel.  When the tool reaches that very narrow thread relief, with one hand you back the cutting tool out and simultaneously stop the lathe and put it in reverse with the other hand.  If you mess up you will run the cutting tool into the shoulder and probably kill that tool and the shoulder and have to start all over.
Not only that ...you have to do this step over and over until the threads are cut deep enough.


https://imgur.com/QPs8TTI


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## ScottD (Aug 16, 2018)

here is a pot view as I am setting up the threading tool.


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## ScottD (Aug 16, 2018)

oh I forgot to show you that before I thread it I cut the coned bolt recess.  Nothing much there just take a boring bar set to the correct angle and cut the 30 degree cone to the manufacturer spec of .135" deep. I use this handmade gauge to measure to make sure the bolt face has clearance (.005").


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## ScottD (Aug 16, 2018)

here is a top view of the threading tool 





and after threads are cut they are measured over .032 wires.  Basically you take three .032 wires and put two on one side and the third on the other side between those two and measure across them.  It helps to poke them down in some foam and hold them on the other side with a rubber band unless you have about 4 hands.


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## ScottD (Aug 16, 2018)

So that is the chamber end completed.  I run a piece of 240 emory cloth with some oil and polish the chamber LIGHTLY especially where the cone meets the chamber. 

Now take it out of the chuck and flip it around to the muzzle end.
Put the muzzle end in the chuck and readjust to get a good zero again (this time right at the muzzle)





And then cut the muzzle with a good sharp tool from the bore out.





Then I use 240 emory cloth and oil and gently touch the bore edge running the lathe forward then reverse.

That's it. she is done.

Well if you don't use a tuner which I do so I have to thread the muzzle end too - much the same way as the chamber end.


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## ScottD (Aug 16, 2018)

Put the barrel in the vise and screw the gun onto the barrel.  I like to use grease as an anti-seize, a recommendation of the action manufacturer (kelbly's).


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## Mr Bya Lungshot (Aug 16, 2018)

I watched live action but you lost me at superglue and got me back with your last post screwing it in. Lol. 
Very interesting and thank you so much for posting the fine details of how it’s made.


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## Jester896 (Aug 16, 2018)

I have been fortunate to watch my builder do 3 for me.  Artists at work for sure!


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## rayjay (Aug 16, 2018)

ScottD said:


> Put the barrel in the vise and screw the gun onto the barrel.  I like to use grease as an anti-seize, a recommendation of the action manufacturer (kelbly's).


Not BR shooters should take notice that the scope is missing it's turrets.


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## sbroadwell (Aug 16, 2018)

Wow, thanks, that is interesting.
I think I better stick to making fishing rods!


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## ScottD (Aug 17, 2018)

FYI - I uncrewed the old barrel and screwed the new one on.  First shot was within 2" at 100 yards.

Yes there are no turrets on the scope - they were removed and the scope was made "fixed" with epoxy.  All the adjustments are done away from the scope at the base.

And yes normally you would remove the action to install the barrel, but i cannot very easily because the action doesn't have action screws, it is epoxied in the stock.

You can see the tuner on the end of the barrel.


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## jglenn (Aug 17, 2018)

great article Scott.. interesting idea on the barrel sleeves.. I use brass wire to hold my barrels in a four jaw.. love the warner threading tools. I've used Mobil one wheel bearing grease for years as my anti seize never had an issue.. Try the Viper threading oil ..works great but really smokes and stinks. LOL

BTW, that tomato stake you gave me turned into a pretty good light bullet 300 Savage hunting rifle ( Rem. model 7)

Jimmy


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## Darkhorse (Aug 19, 2018)

This post really brought back some old memories. I started work in a Tool & Die shop at 18, was a T&D journeyman for the AF and did a stint in Numerical control, some 40 years associated with tooling and manufacturing structural components.
I really like how you used the sleeves to hold the barrel, never seen it done that way but it makes perfect sense.
Haven't seen a thread gage in decades, we used them to hand grind a HSS cutter for threadcutting. I agree about chasing threads it can be nerve wracking. It's much easier to program a thread cutting macro into a NC machine and let it do the work with carbide threading inserts.
We did check some threads with wires but It's been a long time ago, I personally remember having problems holding 3 wires and a micrometer.
We used 4 jaw adjustable chucks. I've never seen a 3 jaw with adjustments for each jaw.
Very well done informative post. I enjoyed it.


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## ScottD (Aug 22, 2018)

Jimmy,
I am glad to hear that barrel has found new life.  I have another worn out 30 cal. maybe I will make one for myself.

The adjustable 3 jaw chuck is really just like mounting a 3 jaw chuck into a four jaw chuck.  In this picture you can see two of the four adjustment screws on the base plate of the chuck.  Basically you just chuck up the piece in the three jaw like normal and then use the four adjustment screws in the base like you would on a four jaw.


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## Darkhorse (Aug 22, 2018)

So, you are moving the entire 3 jaw chuck around the axis of the part instead of adjusting each jaw separately? I can see how that method works just never seen it done.


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## jglenn (Aug 22, 2018)

seems like southbend had one of the adjustable 3 jaws way back... they were a bit pricey if I remember correctly


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