Bore straightness, important?

[10XSHOOTER]

I know they are VERY expensive. But has any barrel maker thought of using a laser to bore their barrels?
Laser would burn a straight hole thru the barrel. Then rifle it?????

 

[urbanrifleman]

I can’t imagine any circumstance where I would stick a hardenned pin down a barrel.

They are what they are. As was mentioned before, some look downright scary when you look through the ID as the barrel is turning in the lathe.

years ago, I thought I could use my machinist skills to ascertain which barrels were good. With the cut rifled barrels I shooters, Kriegers and Bartliens, they hold the ID groove dimensions extremely close, so close it is an exercise in futility trying to figure out if there actually is any.

I buy them, chamber them, and shoot them.

This may be the best gunsmithing post I have read in a while...

 

[bugman]

Not if chambered right. I have seen zero correlation between accuracy and bore straightness.

that is what scope turrets are made for. lol.

 

[Stan Taylor]

How is the 30 thou determined? What are reference points used.

That’s a good question ,Dave here’s something to look at if the cutting oil viscosity is not good and warm here’s what happens on a 17 caliber when you try to drill it.
This is what happens in a deep hole 27 1/2 inches long I couldn’t even attempt to ream this hole probably would break the reamer I’m talking about a bore reamer .

 

[Lucky Shooter]

Dave Tooley wrote---"What I like is the OD being concentric with the bore."

Do you ever turn the OD to get concentricity with the bore ? I've thought
about that a few times but never did it.

What would be the benefit making such a cut ?

A. Weldy

 

[okie]

That’s a good question ,Dave here’s something to look at if the cutting oil viscosity is not good and warm here’s what happens on a 17 caliber when you try to drill it.

I would be willing to bet that it would shoot great. just turn it up or down please!

 

[okie]

Dave Tooley wrote---"What I like is the OD being concentric with the bore."

Do you ever turn the OD to get concentricity with the bore ? I've thought
about that a few times but never did it.

What would be the benefit making such a cut ?

A. Weldy

I think probably because it would be a lot easier to dial it in...

 

[Stan Taylor]

I think probably because it would be a lot easier to dial it in...

Okie
That’s a good one ,that exit hole I would venture to say is at least.165 thousands out of the center because that’s what the diameter of the drill is for a 17 caliber is.

 

[Dusty Stevens]

Is that my 17cal?

That’s a good question ,Dave here’s something to look at if the cutting oil viscosity is not good and warm here’s what happens on a 17 caliber when you try to drill it.
This is what happens in a deep hole 27 1/2 inches long I couldn’t even attempt to ream this hole probably would break the reamer I’m talking about a bore reamer .

 

[ChesterS]

Curvature? I think they have a pill for that now!

 

[Stan Taylor]

Is that my 17cal?

Hell Dusty I wouldn’t even sell that one to Joe Biden.LOL

 

[sdean]

Curvature? I think they have a pill for that now!

A barrel with peyronies disease

 

[AccelR8]

That’s a good question ,Dave here’s something to look at if the cutting oil viscosity is not good and warm here’s what happens on a 17 caliber when you try to drill it.
This is what happens in a deep hole 27 1/2 inches long I couldn’t even attempt to ream this hole probably would break the reamer I’m talking about a bore reamer .

I hear Savage straightens their barrels. When in the process, I don't know

 

[DaveTooley]

Dave Tooley wrote---"What I like is the OD being concentric with the bore."

Do you ever turn the OD to get concentricity with the bore ? I've thought
about that a few times but never did it.

What would be the benefit making such a cut ?

A. Weldy

I've been doing this a long time. I have experience with more than a handful of precision barrel makers. Some you've never heard of. Cut and buttoned. One thing they all had in common. They all shot well. Grant you some shot better at times but it was not brand specific. All had their own personalities as you would expect. Probably the only barrel maker who had a leg up on everyone else in his era was Pat McMillan.
The barrels I predominantly use now are the best I've ever used in regards to concentricity. I've chambered barrels where the bore was .050" off center on the muzzle. One was on an noncontoured blank. Indicate the throat, indicate the muzzle in the bore and went to work. I had to change my setup, indicate the OD, to blend in a muzzle break but the barrel shot fine.
Back to your question. If the barrels you're using have enough runout that you're concerned about it then maybe you should consider changing manufactures. I can't give you a go/no go number. I know when I cut a barrel to length I expect a change in concentricity. Less for cut rifled barrels vs button rifled. 5-10 maybe 20 thou wouldn't bother me.
I use a gage pin when dialing in the muzzle. I use a .0005" under pin. No danger of marring the surface of the lands. Before anyone's head explodes calculate the angular misalignment in say a 26" barrel that may or may not be out 2 1/2 tenths.

 

[DaveTooley]

That’s a good question ,Dave here’s something to look at if the cutting oil viscosity is not good and warm here’s what happens on a 17 caliber when you try to drill it.
This is what happens in a deep hole 27 1/2 inches long I couldn’t even attempt to ream this hole probably would break the reamer I’m talking about a bore reamer .

Stan a couple of questions.
1. Could you cut it off and put a new center in it?
2. Then continue the manufacturing process say after truing the OD with the ID?

 

[Stan Taylor]

I hear Savage straightens their barrels. When in the process, I don't know

I can take a barrel blank with a reamed hole that the bore is crooked and straighten the hole and due to the button rifle process after it’s stress relieving it will go back crooked that’s why we try not to let the hole go out of there that’s not relatively straight.

 

[Stan Taylor]

Stan a couple of questions.
1. Could you cut it off and put a new center in it?
2. Then continue the manufacturing process say after truing the OD with the ID?

After inspection of that hole I doubt I could have reamed it I could machine a new center an possibly get a straight 50 caliber hole threw it but that’s a maybe it’s already went to scrap anyway.
You made a very valid point on the inside to outside if you’re working off a inside outside geometry that’s pretty dead on that makes your job a lot easier.

 

[AccelR8]

I can take a barrel blank with a reamed hole that the bore is crooked and straighten the hole and due to the button rifle process after it’s stress relieving it will go back crooked that’s why we try not to let the hole go out of there that’s not relatively straight.

Yeah I was joking when I wrote that. I know you do good work.

I was watching an old video somebody put on the u tube. How a Rifle is Made or something. The narrtion of the video went "the barrel is drilled and then the rifling is pressed in" I thought hmm, must be Savage. That explains the railroad tracks. Watched a bit more, yup, Savage factory.

 

[urbanrifleman]

I've been doing this a long time. I have experience with more than a handful of precision barrel makers. Some you've never heard of. Cut and buttoned. One thing they all had in common. They all shot well. Grant you some shot better at times but it was not brand specific. All had their own personalities as you would expect. Probably the only barrel maker who had a leg up on everyone else in his era was Pat McMillan.
The barrels I predominantly use now are the best I've ever used in regards to concentricity. I've chambered barrels where the bore was .050" off center on the muzzle. One was on an noncontoured blank. Indicate the throat, indicate the muzzle in the bore and went to work. I had to change my setup, indicate the OD, to blend in a muzzle break but the barrel shot fine.
Back to your question. If the barrels you're using have enough runout that you're concerned about it then maybe you should consider changing manufactures. I can't give you a go/no go number. I know when I cut a barrel to length I expect a change in concentricity. Less for cut rifled barrels vs button rifled. 5-10 maybe 20 thou wouldn't bother me.
I use a gage pin when dialing in the muzzle. I use a .0005" under pin. No danger of marring the surface of the lands. Before anyone's head explodes calculate the angular misalignment in say a 26" barrel that may or may not be out 2 1/2 tenths.

I have really enjoyed working on unturned blanks lately. Mine are always turned centered to the bore on both ends after I contour them.

Just for the sake of discussion... If you hold a barrel on both ends, and both ends are concentric to the bore, the barrel is say 30" total in length, considering even a slightly curved barrel, what would be the angular misalignment of one end? Say, it has 30 thou of total curve (which I doubt) the number is incredibly small. About .06 degrees of "run out".

At 3" inside the bore that would be .003" for the example 30 thou of curve. 1 thou per inch from the starting point, if the starting point were the end of the barrel.

 

[Stan Taylor]

@DaveTooley
After a drilled barrel is reamed you pick up more light rings as you look through the bore if a barrel is almost dead nuts Straight when you look through that bore you visualize it like A target those target rings are concentric that’s a straight hole and if it’s not straight you will see this According to how bad it is look at this little red circle in this target that’s how bad that 17 caliber exit hole was.