Straight barrel

[elf]

I have heard references to a new barrel being straight. What does this mean? Can the bore be crooked? How is it measured? If the bore is not straight, will the manufacturer take it back? I am talking about custom - not factory barrels.

 

[L.Sherm]

I'm sure there referring to the bore straightness from end to end. None are perfect some are better than others.
You here of Smith's talk about indicating in the bore at 12 or 6 o'clock it's what I call the "crescent " of the barrel.

 

[J E Custom]

Barrels are Deep Hole drilled and sometimes it is not straight. In the old days and even now, some barrel makers straightened the bore by bending the outside of the barrel on a barrel straightener. (A special tool for this operation).

With the improvements of today's tools this is not as bad and often doesn't need any straightening, But a good Gunsmith will check to see how straight it is and then decide if it needs to go back.

Different barrel makers have different rejection specs. ranging from .000 TIR to as much as .007. I don't believe that .001 to .002 has much of an effect on accuracy but don't like any if I can get it. Any more than that is not acceptable to Me.

It is not an easy set up to do it right, but well worth the effort. All dimensions are based on the bore Only, and the Outside of the barrel may have to be turned after the bore is deemed straight or you will have different wall thicknesses down the bore that are effected by heat.

The other reason for checking Straightness is to monitor the quality of different barrel Brands. Some brands are consistently/always beyond My limits and I just won't build using them. Truthfully, I don't know how much is bad but I do know that no run out is good.

J E CUSTOM

 

[Edd]

JE, I am interested in how you check a barrel for straightness. Based on what I've read, if you only use barrel blanks with less than .002" runout, you are out of business.

 

[J E Custom]

JE, I am interested in how you check a barrel for straightness. Based on what I've read, if you only use barrel blanks with less than .002" runout, you are out of business.

So far I have been very happy with using Grizzly Rods in both ends of the bore with the barrel mounted in the lathe. I have eliminated certain brands of barrels that were consistently poor by this method
and just don't use them any more. All barrels are not created equal.

With the proper bushing and a pair of good dial indicators for each end I try to balance both indicators. (Zero) if both ends have .0005 max run out then the total is .001 for approximately 16'' the total length of the grizzly rods engagement in the barrel.

If 8'' of barrel is unmeasured you have to assume that it adds a total of.00025 (1/2 the measured rod length) to the .001 measured. this is not the last word in TIR but it is very close and using the same method I have found barrels with more than .050 thousandths that you could actually see the curve if looked at with true north light.

I once had a barrel that I found .0075 run out by this method and sent it back to the builder without telling him how much run out the barrel had. he returned my call and said that it was within spec. and only had .007 (.005 to .007 was industry standard) so he confirmed that I was not very far off. (I still didn't use his barrels)

My method may not be perfect but it does get me very close. I tried the straight precision ground rod for the caliber buy inserting it in the bore and measuring how far it could go down the bore before it stopped and measuring the amount left outside the barrel on each end minus the total length of the barrel. I did not like it because it depended on feel to much. and the numbers left to much to guess/add.

I have found barrels with almost no run out and some that were not measurable. It does take some time, but I am retired and time is not important if it means I get a better job.

I Don't know what method you use but would be glad to hear how you do it and I may learn a better way. Always open to a better method.

J E CUSTOM

 

[YZ-80]

So far I have been very happy with using Grizzly Rods in both ends of the bore with the barrel mounted in the lathe. I have eliminated certain brands of barrels that were consistently poor by this method
and just don't use them any more. All barrels are not created equal.

With the proper bushing and a pair of good dial indicators for each end I try to balance both indicators. (Zero) if both ends have .0005 max run out then the total is .001 for approximately 16'' the total length of the grizzly rods engagement in the barrel.

If 8'' of barrel is unmeasured you have to assume that it adds a total of.00025 (1/2 the measured rod length) to the .001 measured. this is not the last word in TIR but it is very close and using the same method I have found barrels with more than .050 thousandths that you could actually see the curve if looked at with true north light.

I once had a barrel that I found .0075 run out by this method and sent it back to the builder without telling him how much run out the barrel had. he returned my call and said that it was within spec. and only had .007 (.005 to .007 was industry standard) so he confirmed that I was not very far off. (I still didn't use his barrels)

My method may not be perfect but it does get me very close. I tried the straight precision ground rod for the caliber buy inserting it in the bore and measuring how far it could go down the bore before it stopped and measuring the amount left outside the barrel on each end minus the total length of the barrel. I did not like it because it depended on feel to much. and the numbers left to much to guess/add.

I have found barrels with almost no run out and some that were not measurable. It does take some time, but I am retired and time is not important if it means I get a better job.

I Don't know what method you use but would be glad to hear how you do it and I may learn a better way. Always open to a better method.

J E CUSTOM

Thank you for this description on the topic, Sir. Interesting and enlightening.