Barrel Blank Curve

[Coyote Shadow Tracker]

All barrel blanks have a (Curve) in them from manufacturing Most rifles are hand lapped and then measured by Sheffield Air gauging helps with inside dimensions from one end to the other of the barrel.
What is the best & easiest way to determine the curve in a barrel blank so it can be indexed when finished? Preferably indexing the barrel at 12:00 up when finished. That way you only have to work against gravity when shooting.
Thanks
Len & Jill

 

[BillLarson]

Len,you are correct.... barrel bores are not always perfectly straight..
First make sure barrel o.d (outside)and i.d (inside) are concentric within .003"
If they are not identify and mark high spot.
I set mine up in a set of v-blocks index by hand.A piece of steel/alum.angle will work....you can see less than .005" runout.
A white background to look at helps.or look at sky..
Mark high spot.
this is the way I do it.
set up in lathe machine receiver threads.
screw receiver on to see how it is in relation to high spot.
machine barrel shoulder to time receiver and barrel as desired.
chamber last to get headspace correct.
Doing this solves the sometime occurrence of scopes using alot-all of travel to compensate for worm hole bores.
In theory if bore is straight,receiver,mounts,rings aligned with bore,scope reticle centered,very little ajustment should be needed....
Hope this helps.... I,m sure I forgot something....
Let the flames begin....
bill

 

[Alex Wheeler]

I time every barrel I chamber. You find the high spot when its dialed in in the lathe. Its not a curve though, the drill tends to wander more like a helix and its usually worse on the muzzle end. I have been paying attention to this for years in our 1k BR rifles and have not seen any correlation with straightness and accuracy.

 

[Coyote Shadow Tracker]

Len,you are correct.... barrel bores are not always perfectly straight..
First make sure barrel o.d (outside)and i.d (inside) are concentric within .003"
If they are not identify and mark high spot.
I set mine up in a set of v-blocks index by hand.A piece of steel/alum.angle will work....you can see less than .005" runout.
A white background to look at helps.or look at sky..
Mark high spot.
this is the way I do it.
set up in lathe machine receiver threads.
screw receiver on to see how it is in relation to high spot.
machine barrel shoulder to time receiver and barrel as desired.
chamber last to get headspace correct.
Doing this solves the sometime occurrence of scopes using alot-all of travel to compensate for worm hole bores.
In theory if bore is straight,receiver,mounts,rings aligned with bore,scope reticle centered,very little ajustment should be needed....
Hope this helps.... I,m sure I forgot something....
Let the flames begin....
bill

Bill
Thanks kind of do it the same way. Using Krieger & Bartlein I find them just about tight one, but always check. Does help with scope travel and want that "Curve" to be vertical rather that Horizontal.
Just checking to see for different ways to do it. Sometimes someone has better way to do things.
Thanks
Len & Jill

 

[Coyote Shadow Tracker]

I time every barrel I chamber. You find the high spot when its dialed in in the lathe. Its not a curve though, the drill tends to wander more like a helix and its usually worse on the muzzle end. I have been paying attention to this for years in our 1k BR rifles and have not seen any correlation with straightness and accuracy.

Alex
You are correct
Thanks much!

 

[cohunt]

Has anyone ever put the "curve" opposite of the rifling twist to counteract the drift ? Or is it better to just put it up

 

[Coyote Shadow Tracker]

Has anyone ever put the :cirve" opposite of the rifling twist to counteract the drift ? Or os ot better to just put ot up

I always put to the top!

 

[Will Gray]

I was born in the wrong century so my work is primitive. I buy barrel blanks from Shilen, keep track of the stamped end so it always becomes the chamber end, I cut at least one inch off each end of the barrel, center drill both ends and then do profiling and threading between centers. I tie the lathe dog to the headstock plate so the barrel remains tight against the center while the chamber end is supported by the stready rest during chambering. I set the chamber depth with reference to the NOGO gauge bevel. All of my barrels use barrel nuts to set the headspace. They shoot mighty fine.

 

[Radman]

Len,you are correct.... barrel bores are not always perfectly straight..
First make sure barrel o.d (outside)and i.d (inside) are concentric within .003"
If they are not identify and mark high spot.
I set mine up in a set of v-blocks index by hand.A piece of steel/alum.angle will work....you can see less than .005" runout.
A white background to look at helps.or look at sky..
Mark high spot.
this is the way I do it.
set up in lathe machine receiver threads.
screw receiver on to see how it is in relation to high spot.
machine barrel shoulder to time receiver and barrel as desired.
chamber last to get headspace correct.
Doing this solves the sometime occurrence of scopes using alot-all of travel to compensate for worm hole bores.
In theory if bore is straight,receiver,mounts,rings aligned with bore,scope reticle centered,very little ajustment should be needed....
Hope this helps.... I,m sure I forgot something....
Let the flames begin....
bill

Well spoken.

 

[kgunz11]

I chamber through the headstock and always mark TDC. At that point its easier to time the barrel to TDC with the shoulder. Then punch in the chamber. If all the other parts are straight, there should be very little windage dialed into the scope.

 

[kgunz11]

I was born in the wrong century so my work is primitive. I buy barrel blanks from Shilen, keep track of the stamped end so it always becomes the chamber end, I cut at least one inch off each end of the barrel, center drill both ends and then do profiling and threading between centers. I tie the lathe dog to the headstock plate so the barrel remains tight against the center while the chamber end is supported by the stready rest during chambering. I set the chamber depth with reference to the NOGO gauge bevel. All of my barrels use barrel nuts to set the headspace. They shoot mighty fine.

I don't remove any length from the chamber end. I want as much meat in the shank as I can get. For my personal rifles, I'll order an extra inch of shank. I believe the rigidity provided by the full diameter makes the tune windows a little bigger.

Also, the lap is cut out of the chamber end when the chamber is cut.

 

[jarnold37]

I was born in the wrong century so my work is primitive. I buy barrel blanks from Shilen, keep track of the stamped end so it always becomes the chamber end, I cut at least one inch off each end of the barrel, center drill both ends and then do profiling and threading between centers. I tie the lathe dog to the headstock plate so the barrel remains tight against the center while the chamber end is supported by the stready rest during chambering. I set the chamber depth with reference to the NOGO gauge bevel. All of my barrels use barrel nuts to set the headspace. They shoot mighty fine.

Just wondering. When chambering between centers, and the 60° center is removed, how can you keep the barrel dialed in with a steady rest. I have tried roller bearings and bushings with steady rest and the indicator will sometimes show as much as 20 thousands runout. My expensive high quality lathe had the tailstock 2.7 thousands high when new.. Even truing tail left and right could not make up for the high up and down. So I had my tailstock ground to 9 tenths high. Started chambering in headstock with quality 6 jaw chuck. But with long cartridges there is some runout in the tailstock quill in its entire stroke. And it seems the chamber end being indicated is more critical than the muzzle end in outboard of spindle because the bore is not straight. It seems that the 6 inches of the chamber end indicated to 1 or 2 tenths will ensure that the chamber is concentric with the bore where the reamer is cutting and the muzzle need not dialed in per se. Between centers the muzzle bore is centered but the important end is off in the steady rest and the tailstock is also off. I am not arguing, just questioning.

 

[Will Gray]

My lathe is an OLD Craftsman 12" X 36" Cannot get anything larger than 3/4" through the headstock so I have to work with the full lenght of the barrel. I profile the barrel, turn the tenon to size and thread between centers with the steady rest up close to the threads. There I run it with the bronze supports snug, lubed and running smoothly. With the lathe dog tied tightly to the plate, I remove the tailstock and chamber using a floating "center" for the reamer. The reamer seeks the center of rotation. How close to blueprint, I have no idea. I don't measure any of it. I have done maybe 10 ten barrels that way from 223 right up to 416 all with no issues and my rifles are all well under 1" at 100yds, brass looks good, firing pin strikes are in the center of the primers. I believe that having the axis of the bullet exactly matching the axis of the breech end of the barrel is all that really matters. My system seems to do that very nicely. A free floating stiff stock with tight screws all around and correct headspace with a good scope is the best I can do. It is a hobby. I have a 338 barrel coming from Shilen and a 338 EDGE Dave Manson reamer being made (his tools cut steel like ice cream). I pour on lots of oil for all the work. I used bacon grease a long time but have found Mobil 1 5-20 (with 10k miles on it) works just fine. I would enjoy seeing your setup I am sure.

 

[BillLarson]

Just wondering. When chambering between centers, and the 60° center is removed, how can you keep the barrel dialed in with a steady rest. I have tried roller bearings and bushings with steady rest and the indicator will sometimes show as much as 20 thousands runout. My expensive high quality lathe had the tailstock 2.7 thousands high when new.. Even truing tail left and right could not make up for the high up and down. So I had my tailstock ground to 9 tenths high. Started chambering in headstock with quality 6 jaw chuck. But with long cartridges there is some runout in the tailstock quill in its entire stroke. And it seems the chamber end being indicated is more critical than the muzzle end in outboard of spindle because the bore is not straight. It seems that the 6 inches of the chamber end indicated to 1 or 2 tenths will ensure that the chamber is concentric with the bore where the reamer is cutting and the muzzle need not dialed in per se. Between centers the muzzle bore is centered but the important end is off in the steady rest and the tailstock is also off. I am not arguing, just questioning.

To do barrels in steady rest.O.D and I.D
MUST BE CONCENTRIC