Indexing a rifle barrel...

[eww1350]

I have watched the "Gordy Gritters" video on how to chamber a barrel. The idea of indexing the muzzle to the 12 o'clock position is for what reason other than having the muzzle/bore pointing up to give the bullet a higher trajectory from the muzzle.. since the barrel tends to have curves thru the bore why not chamber as usual then determine the bore inside to outside run out at the crown and time the action to that 12 o'clock reading..
In other words the variation we see when we indicate the o.d. and the I.d. at the muzzle could be timed to the 12 o'clock after threading.. and before chambering..
I am not convinced that indexing a barrel per "Gordy's" method makes a rifle more accurate and therefore I do not use his method at this time..
Maybe some of you can convince me otherwise.

 

[savagedasher]

I have watched the "Gordy Gritters" video on how to chamber a barrel. The idea of indexing the muzzle to the 12 o'clock position is for what reason other than having the muzzle/bore pointing up to give the bullet a higher trajectory from the muzzle.. since the barrel tends to have curves thru the bore why not chamber as usual then determine the bore inside to outside run out at the crown and time the action to that 12 o'clock reading..
In other words the variation we see when we indicate the o.d. and the I.d. at the muzzle could be timed to the 12 o'clock after threading.. and before chambering..
I am not convinced that indexing a barrel per "Gordy's" method makes a rifle more accurate and therefore I do not use his method at this time..
Maybe some of you can convince me otherwise.

I think it is the only way to to go time it at 12 or 6 . So the bullet is traveling in a straight line of the scope .
For long range I like at 12 because of the weight on the action .
So it is your choice. Larry

 

[Hengehold]

I have watched the "Gordy Gritters" video on how to chamber a barrel. The idea of indexing the muzzle to the 12 o'clock position is for what reason other than having the muzzle/bore pointing up to give the bullet a higher trajectory from the muzzle.. since the barrel tends to have curves thru the bore why not chamber as usual then determine the bore inside to outside run out at the crown and time the action to that 12 o'clock reading..
In other words the variation we see when we indicate the o.d. and the I.d. at the muzzle could be timed to the 12 o'clock after threading.. and before chambering..
I am not convinced that indexing a barrel per "Gordy's" method makes a rifle more accurate and therefore I do not use his method at this time..
Maybe some of you can convince me otherwise.

Great question. The Long answer to your short question is that indexing a barrel in a 12 o'clock or 6 o'clock position is giving it The best possible state of harmonics to start with.

To illustrate what is happening you can try an exercise with a cleaning rod secured near the handle in a vice. First, Flick the end of the cleaning rod straight up-and-down and watch the pattern of movement of the tip of the cleaning rod until movement comes to a stop. second, try flicking the cleaning rod left and right and watch the pattern of movement of the cleaning rod until the mvmt has come to a stop. You will notice that when you flick the cleaning rod in an up-and-down motion that as the cleaning rod eventually stops whipping up and down it stays in a vertical plane. However, when you flick the cleaning rod in a lateral motion you'll notice that before it comes to rest the whip pattern of the cleaning rod is lateral then circular before eventually making a vertical motion. This cleaning rod is representing the action of a barrel that is whipping while being shot. A barrel that is whipping only in a vertical plane would have only one movement to overcome. A barrel with a lateral movement would eventually have to overcome not just the lateral movement but a circular motion and eventually a vertical mvmt as you will see demonstrated with a cleaning rod.The idea of indexing a bore in the 12 o'clock or 6 o'clock positions can be tested and realized with a barrel mounted rest.

If you were to place a barreled action in a rest and shoot groups rotating 90° after each group you will find that the barrel will shoot groups in a different location for each 90° rotation. In other words the point of impact will change on paper each time you rotate the barrel. At 100 yds I would typically see a point of impact shift of several inches per 90 degree rotation. Additionally, you will find that the groups in the 12 o'clock and 6 o'clock positions will be smaller groups than the groups found in the 3 o'clock and 9 o'clock areas. I have conducted this experiment with about a dozen different smallbore barrels and I have never seen a barrel that did not shoot it's best groups in the 12 o'clock and 6 o'clock positions. The difference in group sizes that I experienced was that the 12 o'clock and 6 o'clock groups would consistently be around half the size of the lateral groups found in the 3 o'clock and 9 o'clock positions. This was true of all ammunition tested from the high dollar Lapua and Eley to the lower-priced SK and Wolf ammunition.

As a sidenote, the rest that I used was a barrel mounted fixture that could absorb some recoil and return to battery in the same position every time and was mounted onto a mill and shot at 100 yards.

This practice of barrel indexing is primarily useful in smallbore where tuning the ammunition to the rifle is not an option. I have conducted the same experiment with high-powered rifles but the rest that I have does not handle the recoil as well as smallbore rifles. When I conducted this experiment with a couple of high-powered rifles I did see similar results as the barreled action was rotated in which the groups found in a vertical plane such as the 12 o'clock and 6 o'clock positions were the smallest groups and the groups found in a lateral plane at the 3 o'clock and 9 o'clock positions were the biggest groups.

My experience with bore indexing has been a trial and error method rather then a measure and cut method. Without conducting a trial and error approach, one would never see the resulting reduction in group sizes for the 12 o'clock and 6 o'clock positions . .

Sorry for the dissertation but I have a unique amount of experience with testing indexed barrels. I hope this helps .

-Trevor

 

[IdahoCTD]

While chambering a barrel the other day I thought about doing a test where you set the barrel back every 45 degrees (changing the index position) to see what effect it has on the long range groups. You would think it would throw them left or right depending on the position of the curve indexing. I'm sure someone else has tried this but I've never read about it.

 

[savagedasher]

While chambering a barrel the other day I thought about doing a test where you set the barrel back every 45 degrees (changing the index position) to see what effect it has on the long range groups. You would think it would throw them left or right depending on the position of the curve indexing. I'm sure someone else has tried this but I've never read about it.

With the new Sunnen honeing honing that some barrel manufacturing are using. The difference is so little it would be hard to time.
The last two was under .005. In 30". When replaceing the barells they shot within .250 of each other. Did they shoot better I couldn't see the difference . But they did have lower ES. Larry

 

[WayneShaw]

What does honing the bore have to do with the drilled hole? Yes it will true/hone/smooth or whatever, but it won't straighten the drilled hole.

What am I missing?

 

[savagedasher]

What does honing the bore have to do with the drilled hole? Yes it will true/hone/smooth or whatever, but it won't straighten the drilled hole.

What am I missing?

Drilling a straight hole 30'' probably never happens . Honeing one straight is simple process .Sunnen has Ben doing it for years in automotive engines . They can put the choke in the barrel where ever they want it.
They drill under size and hone it straight.
Check a new barrel you will see the light rings are even space down the bore .
Larry

 

[IdahoCTD]

I agree that many of them are straighter now but not all of them. The last two barrels I've done were a Wilson and a McGowen and neither were what I would call straight . The Wilson typically shoots in the .3's and .4's for 3 shots in a #4 contour with factory ammo but has shot a few in the low .2's. It is a 6.5 Creedmoor so the quality of factory ammo is pretty good. The McGowen is a light sporter weight also in .260. I'll be curious to see how it shoots as well.

I might have to buy a cheap barrel like a Green Mountain if I decide to test it but there are still some barrels out there from the top makers that aren't very straight. It does seems like the cut rifled barrels are straighter on average. I can see the bore moving when the button is being pulled through it or during contouring. Just because it's straight before that doesn't mean it will be after.

 

[billlarson]

Drilling a straight hole 30'' probably never happens . Honeing one straight is simple process .Sunnen has Ben doing it for years in automotive engines . They can put the choke in the barrel where ever they want it.
They drill under size and hone it straight.
Check a new barrel you will see the light rings are even space down the bore .
Larry

Where are you getting this information..............????.....making a crooked bore straight is a very tuff request......most...barrel mfg`s. don`t own a sunnen hone.......yes some do.... but do they guarantee bore straightness....????
bill larson

 

[Riesel]

Great question. The Long answer to your short question is that indexing a barrel in a 12 o'clock or 6 o'clock position is giving it The best possible state of harmonics to start with.

To illustrate what is happening you can try an exercise with a cleaning rod secured near the handle in a vice. First, Flick the end of the cleaning rod straight up-and-down and watch the pattern of movement of the tip of the cleaning rod until movement comes to a stop. second, try flicking the cleaning rod left and right and watch the pattern of movement of the cleaning rod until the mvmt has come to a stop. You will notice that when you flick the cleaning rod in an up-and-down motion that as the cleaning rod eventually stops whipping up and down it stays in a vertical plane. However, when you flick the cleaning rod in a lateral motion you'll notice that before it comes to rest the whip pattern of the cleaning rod is lateral then circular before eventually making a vertical motion. This cleaning rod is representing the action of a barrel that is whipping while being shot. A barrel that is whipping only in a vertical plane would have only one movement to overcome. A barrel with a lateral movement would eventually have to overcome not just the lateral movement but a circular motion and eventually a vertical mvmt as you will see demonstrated with a cleaning rod.The idea of indexing a bore in the 12 o'clock or 6 o'clock positions can be tested and realized with a barrel mounted rest.

If you were to place a barreled action in a rest and shoot groups rotating 90° after each group you will find that the barrel will shoot groups in a different location for each 90° rotation. In other words the point of impact will change on paper each time you rotate the barrel. At 100 yds I would typically see a point of impact shift of several inches per 90 degree rotation. Additionally, you will find that the groups in the 12 o'clock and 6 o'clock positions will be smaller groups than the groups found in the 3 o'clock and 9 o'clock areas. I have conducted this experiment with about a dozen different smallbore barrels and I have never seen a barrel that did not shoot it's best groups in the 12 o'clock and 6 o'clock positions. The difference in group sizes that I experienced was that the 12 o'clock and 6 o'clock groups would consistently be around half the size of the lateral groups found in the 3 o'clock and 9 o'clock positions. This was true of all ammunition tested from the high dollar Lapua and Eley to the lower-priced SK and Wolf ammunition.

As a sidenote, the rest that I used was a barrel mounted fixture that could absorb some recoil and return to battery in the same position every time and was mounted onto a mill and shot at 100 yards.

This practice of barrel indexing is primarily useful in smallbore where tuning the ammunition to the rifle is not an option. I have conducted the same experiment with high-powered rifles but the rest that I have does not handle the recoil as well as smallbore rifles. When I conducted this experiment with a couple of high-powered rifles I did see similar results as the barreled action was rotated in which the groups found in a vertical plane such as the 12 o'clock and 6 o'clock positions were the smallest groups and the groups found in a lateral plane at the 3 o'clock and 9 o'clock positions were the biggest groups.

My experience with bore indexing has been a trial and error method rather then a measure and cut method. Without conducting a trial and error approach, one would never see the resulting reduction in group sizes for the 12 o'clock and 6 o'clock positions . .

Sorry for the dissertation but I have a unique amount of experience with testing indexed barrels. I hope this helps .

-Trevor

Dang It! ! Just when I was starting to get the hang of putting new chambered barrels on rifles..................and I thought it was safe to get back in the water ........................another problem/shark comes along. I'll never get there

 

[savagedasher]

Where are you getting this information..............????.....making a crooked bore straight is a very tuff request......most...barrel mfg`s. don`t own a sunnen hone.......yes some do.... but do they guarantee bore straightness....????
bill larson

No request is needed . Why would a barrel manufacture advertised their machining advantages.
The shooters will find out what barrels shoot best. And that will be the kind they buy.Larry

 

[savagedasher]

Dang It! ! Just when I was starting to get the hang of putting new chambered barrels on rifles..................and I thought it was safe to get back in the water ........................another problem/shark comes along. I'll never get there

Not a problem when you have the barrel set up just time the action for straight up.. Larry

 

[Rustystud]

Look at Savage Rifles using a barrel nut. Savage still hand straightens barrels and does a pretty good job at it. I eat lunch with Allen Orr at Sightron several days per week. He says by far he gets more calls every week about Savage rifles that max out the scopes adjustments and still will not sight in. Allen was of the opinion that these rifles had their scope screw holes misaligned during the manufacturing process. I told Allen that I had checked many Savage Rifle actions and most were dead nuts in alignment with the bolt. I found that the problem was with the fit up of the barrel using the barrel nut. The slop in the threads, warp in the actions allowed the barrel nut to index the barrel in any given angle. Truing up the face of a Savage action, using a precision ground recoil lug and barrel nut along with paying attention where the muzzle is indexed when the nut is tighten will most often fix scope and point of impact and scope adjustment issues.
Nat Lambeth

 

[JRS]

Not a problem when you have the barrel set up just time the action for straight up.. Larry

How does one time an action for "straight up"?

 

[savagedasher]

How does one time an action for "straight up"?

I said it wrong you time the barrel to the action. When true boring alignment is used a barrel the muzzle end normally is not on true center of the bore
When you chamber you make sure the tennon is cut so when the barrel is tight the muzzle is pointing at 12 . A savage is more difficult to time because of not having a tennon.
The barrel that is straight like the last two it don't matter. A barrel that is as straight as . O05 don't matter. Larry

 

[Eddie Harren]

I said it wrong you time the barrel to the action. When true boring alignment is used a barrel the muzzle end normally is not on true center of the bore
When you chamber you make sure the tennon is cut so when the barrel is tight the muzzle is pointing at 12 . A savage is more difficult to time because of not having a tennon.
The barrel that is straight like the last two it don't matter. A barrel that is as straight as . O05 don't matter. Larry

GOSPEL!

 

[WSnyder]

...and just when you think it's about as bad as it can get it just keeps getting worse!

 

[savagedasher]

...and just when you think it's about as bad as it can get it just keeps getting worse!

That is why it takes longer to indicate in a barrel then it does to do the job. Larry

 

[LHSmith]

Look at Savage Rifles using a barrel nut. Savage still hand straightens barrels and does a pretty good job at it.
Nat Lambeth

Are they still doing that? I remember a picture in one of the gun rags years ago showing the fixture and the Savage employee in the act of straightening a barrel.....awfully crude method. If I am not mistaken, this is creating barrel stress at it's finest.... the phrase "walking the shots" comes to mind. But to John Q. Public who buys a hunting rifle, sights in once to hit a pizza box at 50 yards, then shoots 2 maybe 3 shots every year thereafter..... if she fires everytime....good enough.

 

[LHSmith]

Sometimes you feel like a nut, sometimes you don't. I hate nuts. But then as a retired contractor- I despise DIY'er's....they'll screw anything up and then want you to fix it for nothing.