Barrel Tollerances
- Thread starter Curious
- Start date
Dave Tooley
Active member
Same here. I know of no barrel maker willing to invest in a laser system. I'm sure somewhere else in industry there are laser systems in use for other products. To my knowledge only the government can/is occasionally testing rifle barrels.
JerrySharrett
Senile Member
First off, there is no relationship between barrel bore straightness and accuracy. I've seen really crooked barrels that look like a 2girl jump rope shoot great and barrels that had no perceiptsble lope shoot crappy.
I once took a really crooked looking barrel, cut in into in the middle and measured the variation OD to ID and the difference was a total of 0.013". This doesn't proove anything since I don't know how straight the OD was.
I know one thing though, chamber it with a 26 Nosler and put 95 grains of Rl-33 and that should solve the crooks, and that is minor compared to some of the chamberings Tooley does.
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I once took a really crooked looking barrel, cut in into in the middle and measured the variation OD to ID and the difference was a total of 0.013". This doesn't proove anything since I don't know how straight the OD was.
I know one thing though, chamber it with a 26 Nosler and put 95 grains of Rl-33 and that should solve the crooks, and that is minor compared to some of the chamberings Tooley does.
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B.Larson
New member
jackie schmidt
New member
There are misconceptions about barrel straightness, and just what the term means.
First, most barrels are not "bent", in the classic definition. What they have is an ID that does not run true with it's own self in specific sections of it's length.
This is the product of the initial Gundrilling of the barrel blank. Even the most sophisticated gun drilling machines have tolerances as to how try key straight the drill will progress through the blank. Gun drills tend to drift one way or the other as they proceed down the blanks length. That means one section of the barrels ID will show run out, while anther section just inches away might show run out in a complete different direction.
Picture chucking up a piece of steel, turning it for a few inches, then stopping and readjusting the chuck so that turned section tons out a few thousandths, then continue a few more inches, stopping again, readjusting the check so it runs out a couple thousandths in a different direction, then proceed, and so on.
That is what ID of a barrel resembles.
The act of straightening a barrel is a futile effort at best. If a machined part is not machine truly straight with it's own self to begin with, it is virtually impossible to straighten it to where all points run true.
Keep in mid, all subsequent operations in a barrel blank are predicated on how true the initial gun drilled hole is. The reamer will follow that hole, and so will the rifling tool or button, depending on the type of barrel manufacturing proccess.
Just remember. Barrels are not "bent". The ID's simply do not run true with themselves at different points down their length.
First, most barrels are not "bent", in the classic definition. What they have is an ID that does not run true with it's own self in specific sections of it's length.
This is the product of the initial Gundrilling of the barrel blank. Even the most sophisticated gun drilling machines have tolerances as to how try key straight the drill will progress through the blank. Gun drills tend to drift one way or the other as they proceed down the blanks length. That means one section of the barrels ID will show run out, while anther section just inches away might show run out in a complete different direction.
Picture chucking up a piece of steel, turning it for a few inches, then stopping and readjusting the chuck so that turned section tons out a few thousandths, then continue a few more inches, stopping again, readjusting the check so it runs out a couple thousandths in a different direction, then proceed, and so on.
That is what ID of a barrel resembles.
The act of straightening a barrel is a futile effort at best. If a machined part is not machine truly straight with it's own self to begin with, it is virtually impossible to straighten it to where all points run true.
Keep in mid, all subsequent operations in a barrel blank are predicated on how true the initial gun drilled hole is. The reamer will follow that hole, and so will the rifling tool or button, depending on the type of barrel manufacturing proccess.
Just remember. Barrels are not "bent". The ID's simply do not run true with themselves at different points down their length.
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JerrySharrett
Senile Member
And so do a few other commercial builders. But, if you understand metallurgy and material stresses you will know that a straightened barrel without further stress relieving that barrel will unstress itself every time it is shot and its temperature changes. You do not want that.
I've seen barrels that "walk" their POI as they are shot, then as they cool will walk back.
A friend had a VLS Remington that had that problem. In most cases a Cryo treatment will cure that.
One big advantage of Cryoing over reheating to relieve stress is that the Cryo process has no ill effect on the metal surface where reheating can.
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