barrel bore is non-centric

[BeaverMeat]

What is the effect of a non-centric bore. I have a rifle that is off by 0.025mm (0.01") to the right (down range)

Problem? Or see how it shoots?

 

[Ardent]

I'm most interested in learning how you determined this. As always, shoot and see, you'll never get an answer here. Now, the science if you will.

 

[Claven2]

For many years, Mauser built fine rifles with integral ribs machined into the barrel tops, which in effect produces an eccentric bore. Those rifles shot fine.

While it is not an ideal situation on a round-barrel gun (due to accept alignment more than anything), there are many other factors that have a more real effect like ammo quality, action trueness, bedding, torque on action screws, etc.

The only way to know how well it shoots is to shoot it.

 

[Boomer]

A barrel can suffer all sorts of ills and still shoot well provided the bore is tight at the muzzle. I'm not sure that I understand what the particular malady of your barrel is, but if its simply a matter of the bore not being centered in the barrel, that is usually more of a cosmetic issue than it is a problem which manifests at the target. If on the other hand, you believe the bore is non-concentric, that is out of round, the situation is less than ideal with respect to theoretical precision, but the proof is in the shooting.

 

[BeaverMeat]

I'm most interested in learning how you determined this. As always, shoot and see, you'll never get an answer here. Now, the science if you will.

Visual inspection: "Hey that looks off center"

Measurement: "Will you look at that, it is off center"

Conclusion: It's off center.

 

[Outwest1213]

Visual inspection: "Hey that looks off center"

Measurement: "Will you look at that, it is off center"

Conclusion: It's off center.

Your Looking down your barrel and you can tell its off center by .025mm? Didn't know a human eye could pick that up.

 

[Mike Webb]

I think he means the barrel wall is slightly thicker on one side than on the other so the bore is actually not in the center of the OD.

 

[c-fbmi]

BM...........this is actually way more common than one would think. It has no ill effect on the shootability of the barrel and usually very little to do with the accuracy. I have seen the bore up to 40 thou (1.0 mm) off center and still shoot sub MOA groups.

 

[landphil]

0.025mm = 0.001", not 0.010" like you posted. Which is it?

 

[cody c]

0.025mm = 0.001", not 0.010" like you posted. Which is it?

I suspect he meant .25mm, as said, .025mm would be hard to see.

 

[dimeN]

i'd imagine if there was alot more metal there.. it would make a difference when the barrel is heated up alot .... don't think it would make abit of difference under normal circumstances

 

[Baribal]

That's very common with german guild guns of the interwar era. I've seen rebored 9x57 with huge run out but surprisingly, they shot pretty weĺl...

 

[Mauser98]

The photos below show the opposite ends of a 3.5" piece of a 9.3mm barrel that I kept when I had the barrel shortened. That rifle shot very well before and after shortening. It continued to shoot well even after I had the barrel re-profiled so that the bore was centered.

 

[Mike Webb]

Wow, that one is out a long ways.

 

[BeaverMeat]

i'd imagine if there was alot more metal there.. it would make a difference when the barrel is heated up alot .... don't think it would make abit of difference under normal circumstances

That's what I figured. For a hunting rifle it's a non-issue (unless is shoots like crap)