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bradders

Turning and chambering a barrel

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This is something I've been planning to do for some time, so today was the day.

I'm building a rifle with a 20" barrel, so thought I'd show you a How-To from scratch.
Note: This is only one way to do this, there are many correct ways, and there are plenty of wrong ways.
This is one of the correct ones
First things first, a nice cup of tea, served in a very nice Bradley Arms mug
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Current barrel stock
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When I order my blanks from Sassen, I get them unprofiled and made to max length, in this case around 31". Generally on a job like this, I set up and chamber before cutting to length, in case anything goes awry and I have to start again
Dialling in the muzzle end with a spider attachment
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Indicating the chamber end. Each division is .0005" or 1/2 thou to me and you, and we are looking for better than that.
Here I am using a dial gauge on the lands and grooves, but you can use a Range or indicating rod....I just prefer it this way
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Facing off
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First cut
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Turned to 1"
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Thread tenon turned to .812"x.620"
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Cutting the thread relief
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Squaring the threading tool
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Touching off
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Setting the compound slide to '0'
The slide is set at 29.5 deg (actually reading 59.5 deg on mine, and we're going to go in on this dial until approx 4.6
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Zero the DRO
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Select the feed
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Ghost cut to check all is set correctly
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First pass
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A few minutes later and we have finished threading and cut a 60 deg lead (feed ramp) and made a quick polish
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A final check for length of tenon
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Extn screwed on
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Now we get ready to chamber.
At this point I have a roughing reamer with a correctly sized pilot.
The pilots come in sets, and the idea is to find the one that fits your bore the best.
Note: it is not uncommon for bores to get tighter, and that means changing the pilots as you go. Likewise they can become looser, but that is practically impossible to detect
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Here I am using a reamer stop set to a pre-determined depth and am also using a Bald Eagle floating reamer holder
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Almost there
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Now I switch to the finishing reamer and swap the pilot onto it.
In this case I am using a .223 Wylde reamer from PTG that I use for 2nd stage reaming.
I have a newer reamer that I use only for the final .010" cut, and this preserves it, bearing in mind that the majority of my work is with ,223 calibre barrels
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Final cut reamer with new PTG CiP gauges, stripped bolt and barrel extn
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Checking progress
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Finally, with headspace set, the barrel extn is torqued on, a final pass with the reamer (as chambers can get choked with torquing) check headspace again and polish the chamber
Job done
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Now we remove the barrel, and measure for length + .040" and cut on the bandsaw
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Back in the lathe and indicate for the muzzle
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Face off
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Cut a 30 degree relief at this point, so the barrel will run true on a live centre
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Indicate the chamber end. You will see that I do this part while clamping on the extn. This also gives you a shoulder/datum to work from, and from here to the muzzle is easy to measure 19.38" for this 20" barrel (remember the extn tenon is .620" which makes up the rest of the 20" OAL)
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Turn, turn and turn some more
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I always finish the front sight section first
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And this 10 deg part last before muzzle threading
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Turn the muzzle thread part, and make a relief at the rear
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Set feed rate and make a ghost pass to check
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First pass
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Check with ring gauge
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After crowning (not shown as someone turned up and interrupted me) and all work on the lathe is done
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Now, you don't always get a perfect finish when machining, and I usually finish the barrel to a 320 finish, even when Cerakoting (before shot blasting)
But in this instance the customer wants a stainless polished finish, so.....
What I do is mount it in my barrel spinner
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Work it back and forth on the belt sander until all machining marks are gone
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And finally buff on the mop
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Hey presto....a finished shiny barrel
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Interesting post, thanks.

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Brilliant. Very instructive and interesting. Thanks

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excellent post - enjoyed that - what a work of art !!

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Great post, its always interesting to see behind the scenes. My OCD does make me want me to come down and and have a tidy up though

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Thanks for taking the time to do this Mark.

 

I dont have any experience of these type of rifles, what sort of accuracy is demanded from them and over what distance?

 

Do the users reload or use millitary type ammo?

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Thank you for taking the time Mr Bradley!!

 

T

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OK

 

As I said at the beginning of the thread, there's more than one way to turn and chamber a barrel.

I'm always wiling to learn and there's plenty of talented people on here doing similar stuff, so.......if you do it differently to the way I've shown, then why not post it up and let us all see it

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.

 

Hi Bradders

 

Very informative and very interesting for someone like me

who has an engineering background and who enjoys it watching

a craftsman at work.

 

Out of interest do the blank barrel's come pre rifled?

 

ozone

.

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.

 

Hi Bradders

 

Very informative and very interesting for someone like me

who has an engineering background and who enjoys it watching

a craftsman at work.

 

Out of interest do the blank barrel's come pre rifled?

 

ozone

.

 

Yes

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.

 

Hi Bradders

 

Very informative and very interesting for someone like me

who has an engineering background and who enjoys it watching

a craftsman at work.

 

Out of interest do the blank barrel's come pre rifled?

 

ozone

.

:D

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As I said Bradders good post and thank you for sharing.

 

You know if your clocking off the outside of the barrel i.e. behind the headstock, can you "assume" the hole is in the middle or would you use a spud up the rifling to clock off from or is there a better method?

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