Barrel Indexing
- Thread starter cortezit
- Start date
Dick:
Yes, if a barrel is not straight then indexing will somewhat help depending on how bad the barrel is to start with...The more crooked the barrel the better the improvements you will see but don't confuse these kinds of "remedies for improving accuracy" with something that needs to be done to every rifle..You can also improve accuracy from a bad barrel by adding weight to it at different areas along the barrel and in other ways. Keep in mind that "Indexing" is not the holly grail, you are just artificially compensating for irregularities of a BAD barrel and a BAD BARREL has no place in precision and benchrest shooting if you are serious about it.
There are ways of straightening barrels, I have seen a tool as mentioned in a previous post on this same thread (tool similar to an aluminum arrow straightener) that is being used by FX at their factory and by some other British gunsmiths and tuners...I have never straightened a barrel with such a tool but I have seen it done and I have seen the results of doing it...
Many years back I bought a new .22 RF barrel for a test gun that was like .008" off between both ends, it shot OK but not even close to what is needed to BR...This barrel was going to be trashed and replaced, but chatting with my friend Ed Shilen he very kindly offered me to give it to one of his guys at the shop in an effort to straighten it as much as possible...He said: "We don't straighten our barrels, they are either straight or trashed...straightening is time consuming but it sure can be done"...A few days later I got the barrel with about 002" if I don't remember wrong and all I did was to give it a pass on my lathe to clean some tool marks and even out the outer surface, I then re-crown it and chambered it with a then popular ELEY chamber...That barrel turned out to be a killer barrel as we used it on a testing gun shot from a vise.
To specifically answer to your question about how to get on hold of straight barrels...The caliber that you are shooting and where you are located are the issues that mandate. Here in the USA we are spoiled, we can buy outstanding barrels in about any caliber from premium manufacturers and it has been my experience that those cream of the crop manufacturers produce very straight barrels...If you go to Walther in Germany or Walther-Lothar in the USA, get their premium Match Grade barrels; I have never seen one that doesn't shoot...In Europe you have Walther, Feinwerkbau, Anschutz, BSA and even CZ produces hammer forged barrels that have nothing to be ashamed of.
Whatever you get, before mounting that barrel on your gun check it straightness...I do it mounted on my lathe between the choke and the spider and using range rods/.0001 dials...If in the USA and you are buying from someone like Shilen, Benchmark, Muller, Lothar etc. to have the warranty that if the barrel is not straight they will replace it.
The one problem shooters encounter in the US is that these top barrel manufacturers mentioned don't produce .177 caliber pellet barrels, they do produce .17 RF but the dimensions are different and most of them are reluctant to produce only one barrel...A different story is if you ask them to produce a batch of barrels (I have been told that setting up tooling is the big issue).
I shoot a Shilen Ratchet .177 on my Steyr LG-110, Ed very kindly made it for me when we were doing some vibration dampening testing some 12-15 years ago and after we finished our work I kept this barrel...I installed a Benchmark .22 on a friend's RAW and this barrel out of the box was one of the straightest barrels I have seen. If you are looking for .22 and larger calibers (.25 & 30) then your options in the US are much broader...I can't speak for Europe and other continents.
Keep in mind that Air Benchrest shooting can be done with .22 and that some .22 Rimfire VERY TIGHT normal production barrels work well in pellet guns, so there is no excuse for not finding good straight barrels...The only limitations might be our wallets...
Besides a good barrel you need a good tuning...The best balanced gun I have shot in BR has been a Thomas gun I tested 2 months ago...This gun shoots outstanding because Mike selects his barrels very carefully yes, but it also has much engineering and is very well balanced in terms of timing, trigger, pressure, ports, weight, etc.. I bet you that if you buy a Thomas and remove its barrel for mounting it on your gun, your rifle will shoot well, but it will not shoot as well as it did when mounted on the Thomas.
I believe that I have nothing more to say about this indexing topic and I will let other members post their experiences.
Best regards,
AZ
Yes, if a barrel is not straight then indexing will somewhat help depending on how bad the barrel is to start with...The more crooked the barrel the better the improvements you will see but don't confuse these kinds of "remedies for improving accuracy" with something that needs to be done to every rifle..You can also improve accuracy from a bad barrel by adding weight to it at different areas along the barrel and in other ways. Keep in mind that "Indexing" is not the holly grail, you are just artificially compensating for irregularities of a BAD barrel and a BAD BARREL has no place in precision and benchrest shooting if you are serious about it.
There are ways of straightening barrels, I have seen a tool as mentioned in a previous post on this same thread (tool similar to an aluminum arrow straightener) that is being used by FX at their factory and by some other British gunsmiths and tuners...I have never straightened a barrel with such a tool but I have seen it done and I have seen the results of doing it...
Many years back I bought a new .22 RF barrel for a test gun that was like .008" off between both ends, it shot OK but not even close to what is needed to BR...This barrel was going to be trashed and replaced, but chatting with my friend Ed Shilen he very kindly offered me to give it to one of his guys at the shop in an effort to straighten it as much as possible...He said: "We don't straighten our barrels, they are either straight or trashed...straightening is time consuming but it sure can be done"...A few days later I got the barrel with about 002" if I don't remember wrong and all I did was to give it a pass on my lathe to clean some tool marks and even out the outer surface, I then re-crown it and chambered it with a then popular ELEY chamber...That barrel turned out to be a killer barrel as we used it on a testing gun shot from a vise.
To specifically answer to your question about how to get on hold of straight barrels...The caliber that you are shooting and where you are located are the issues that mandate. Here in the USA we are spoiled, we can buy outstanding barrels in about any caliber from premium manufacturers and it has been my experience that those cream of the crop manufacturers produce very straight barrels...If you go to Walther in Germany or Walther-Lothar in the USA, get their premium Match Grade barrels; I have never seen one that doesn't shoot...In Europe you have Walther, Feinwerkbau, Anschutz, BSA and even CZ produces hammer forged barrels that have nothing to be ashamed of.
Whatever you get, before mounting that barrel on your gun check it straightness...I do it mounted on my lathe between the choke and the spider and using range rods/.0001 dials...If in the USA and you are buying from someone like Shilen, Benchmark, Muller, Lothar etc. to have the warranty that if the barrel is not straight they will replace it.
The one problem shooters encounter in the US is that these top barrel manufacturers mentioned don't produce .177 caliber pellet barrels, they do produce .17 RF but the dimensions are different and most of them are reluctant to produce only one barrel...A different story is if you ask them to produce a batch of barrels (I have been told that setting up tooling is the big issue).
I shoot a Shilen Ratchet .177 on my Steyr LG-110, Ed very kindly made it for me when we were doing some vibration dampening testing some 12-15 years ago and after we finished our work I kept this barrel...I installed a Benchmark .22 on a friend's RAW and this barrel out of the box was one of the straightest barrels I have seen. If you are looking for .22 and larger calibers (.25 & 30) then your options in the US are much broader...I can't speak for Europe and other continents.
Keep in mind that Air Benchrest shooting can be done with .22 and that some .22 Rimfire VERY TIGHT normal production barrels work well in pellet guns, so there is no excuse for not finding good straight barrels...The only limitations might be our wallets...
Besides a good barrel you need a good tuning...The best balanced gun I have shot in BR has been a Thomas gun I tested 2 months ago...This gun shoots outstanding because Mike selects his barrels very carefully yes, but it also has much engineering and is very well balanced in terms of timing, trigger, pressure, ports, weight, etc.. I bet you that if you buy a Thomas and remove its barrel for mounting it on your gun, your rifle will shoot well, but it will not shoot as well as it did when mounted on the Thomas.
I believe that I have nothing more to say about this indexing topic and I will let other members post their experiences.
Best regards,
AZ
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Wilbur and Pete:
Both barrels were from the same batch, same steel, same rifling button, same everything and only different degrees of straightness...I don't remember the exact numbers for these barrels but roughly speaking it has been my experience that a barrel with less than lets say .0025 to 003" difference between both ends and assuming the outer surface is concentric to the bore and good bore dimensions with no tight or loose spots tend to shoot well at any "Indexing" point, meaning indexing is fruitless; by the same token enough gathered data and testing proves that no indexed barrel has ever shot better than a straight barrel (coming from the same batch & brand of barrels).
I never gathered enough data for group size vs. straightness in order to develop a straight correlation that would be valid, one thing for sure is that there is no lineal correlation in between the two variables.
Note: It will be very interesting finding out what other members have done to improve the nominal (factory) accuracy of their guns as used for benchrest shooting or for extreme accuracy....Why don't one of you guys start a new thread asking about this topic?
Best regards,
AZ
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Boyd Allen
Active member
A friend makes a practice of casting laps in barrels of factory rifles, custom rifles, and new barrels of the best quality available, for the purpose of "mapping"their interior dimensions. What he has found is that uniformity and correctness of internal dimensions, and finish are very important, and closely related to how a barrel is lapped, which is a one at a time individual proposition, done by hand. I should probably mention that he correlates what he finds by casting laps with how the barrels shoot when dealing with chambered barrels, and spends a lot of time looking through a bore scope for evidence of jacket fouling. He as also done a lot of corrective lapping. He has great aptitude, is totally fearless about trying things, and understands that there are costs involved in gaining the experience to be able to produce reliable results.
There is also the matter of stress relief, particularly for button rifled barrels. Heating and cooling steel may sound fairly simple, but there are things that are hard to quantify and control that can take place is stress relieving ovens, and the necessary equipment to do residual stress measurement by x-ray diffraction is not commonly found in the equipment inventories of barrel manufacturers. In short, for all intents and purposes, in the vast majority of cases we are flying blind and hoping that a standardized procedure will yield uniform results, when in fact it may not.
There is also the matter of stress relief, particularly for button rifled barrels. Heating and cooling steel may sound fairly simple, but there are things that are hard to quantify and control that can take place is stress relieving ovens, and the necessary equipment to do residual stress measurement by x-ray diffraction is not commonly found in the equipment inventories of barrel manufacturers. In short, for all intents and purposes, in the vast majority of cases we are flying blind and hoping that a standardized procedure will yield uniform results, when in fact it may not.
Pete Wass
Well-known member
Thanks AZ
What you have said makes absolute sense and I agree on the re sizing thing. I have seen how great barrels shoot and they will or seem to shoot great with pellets right out of the can; the right lot of pellets, that is. I assume one could infer that a lot # of pellets that doesn't shoot well has heads that are too small or can there be other factors involved?
Regarding barrel straightness; do those who fit barrels for a living send rejects back to the barrel makers or do the fitters have to eat them?
Thanks,
Pete
What you have said makes absolute sense and I agree on the re sizing thing. I have seen how great barrels shoot and they will or seem to shoot great with pellets right out of the can; the right lot of pellets, that is. I assume one could infer that a lot # of pellets that doesn't shoot well has heads that are too small or can there be other factors involved?
Regarding barrel straightness; do those who fit barrels for a living send rejects back to the barrel makers or do the fitters have to eat them?
Thanks,
Pete
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Pete:
One last observation and I will try to answer your question...
It is very important to deal with prime reputable barrel makers, gunsmiths who fit top of the line barrels return barrels to the manufacturers all the time when they are out of specs, these manufacturers usually replace them no questions asked because they don't want bad barrels creating a bad reputation for the brand. Of course, there are mass produced barrels with much looser specifications that fall into what I call "mediocre or crooked barrels" and those are the ones that are frequently straightened and indexed by installers but it is also true that some of these barrels frequently are good shooters and need nothing.
You are right on the money with your statement about pellets...It is MANDATORY to get a good batch of the same size (the one your gun likes) and then maybe weigh them...I recently bought 25 tins (10,000 pellets) of JSB 13.43 gr. Monsters in .177 caliber...I was lucky and the size on these pellets was pretty uniform, I asked one of my guys at the lab to measure them with a laser micrometer as it is faster and more precise than using the optical comparator or air gauging...I got 20 tins of 4.52's and 5 tins of 4.53's. My gun shoots both sizes very well so the size consistency was a very good thing...
Then came weighing...We used a lab grade scale and to my surprise the range went from 13.22 to 13.70 gr....The curve distribution was Normal (Bell). I shoot my Steyr LG-110 FT gun in Benchrest (I made a BR stock for this particular use) and the gun is set for HV at a tad less than 20 ft.lb....At 25 Meters there wasn't than much difference in between the high and low weights of the same head size, you would miss the "X" but you would still shoot a 10 (Indoors testing)...
Now, shooting a low weight 4.52 and then a high weight 4.53 was a different story...One would hit the "X" and the other would be a 9 or a 9 very close to an 8, or a solid 8....For BR shooters these shots are flyers...
I carry a "PELLET GAUGE" (Manufactured by my friend Joe Peacock in TX) in my tool box, I checked-compared the sizes obtained with the laser micrometer with this gauge and it is very, very precise...I mention this because shooters not having access to good laser micrometers or lab grade air gauging, can get one of these Pellet Gauges in the caliber(s) they shoot and measure the head of their pellets for very little money. The tail or skirt of the pellet is unimportant as it will be re-sized by the bore size at the breech when the pellet is loaded...
In my particular case, if I stay with either head size and shoot unweighted pellets at 20 ft./lb. (815-820 ft./sec.) I can still shoot 249's -250's, but no so if I shoot both head sizes and don't weigh pellets....Having said this, measuring the heads is in my opinion more important than weighing, and depending on the distance and power of the gun you are shooting, weighing comes next.
Have a nice weekend,
AZ
One last observation and I will try to answer your question...
It is very important to deal with prime reputable barrel makers, gunsmiths who fit top of the line barrels return barrels to the manufacturers all the time when they are out of specs, these manufacturers usually replace them no questions asked because they don't want bad barrels creating a bad reputation for the brand. Of course, there are mass produced barrels with much looser specifications that fall into what I call "mediocre or crooked barrels" and those are the ones that are frequently straightened and indexed by installers but it is also true that some of these barrels frequently are good shooters and need nothing.
You are right on the money with your statement about pellets...It is MANDATORY to get a good batch of the same size (the one your gun likes) and then maybe weigh them...I recently bought 25 tins (10,000 pellets) of JSB 13.43 gr. Monsters in .177 caliber...I was lucky and the size on these pellets was pretty uniform, I asked one of my guys at the lab to measure them with a laser micrometer as it is faster and more precise than using the optical comparator or air gauging...I got 20 tins of 4.52's and 5 tins of 4.53's. My gun shoots both sizes very well so the size consistency was a very good thing...
Then came weighing...We used a lab grade scale and to my surprise the range went from 13.22 to 13.70 gr....The curve distribution was Normal (Bell). I shoot my Steyr LG-110 FT gun in Benchrest (I made a BR stock for this particular use) and the gun is set for HV at a tad less than 20 ft.lb....At 25 Meters there wasn't than much difference in between the high and low weights of the same head size, you would miss the "X" but you would still shoot a 10 (Indoors testing)...
Now, shooting a low weight 4.52 and then a high weight 4.53 was a different story...One would hit the "X" and the other would be a 9 or a 9 very close to an 8, or a solid 8....For BR shooters these shots are flyers...
I carry a "PELLET GAUGE" (Manufactured by my friend Joe Peacock in TX) in my tool box, I checked-compared the sizes obtained with the laser micrometer with this gauge and it is very, very precise...I mention this because shooters not having access to good laser micrometers or lab grade air gauging, can get one of these Pellet Gauges in the caliber(s) they shoot and measure the head of their pellets for very little money. The tail or skirt of the pellet is unimportant as it will be re-sized by the bore size at the breech when the pellet is loaded...
In my particular case, if I stay with either head size and shoot unweighted pellets at 20 ft./lb. (815-820 ft./sec.) I can still shoot 249's -250's, but no so if I shoot both head sizes and don't weigh pellets....Having said this, measuring the heads is in my opinion more important than weighing, and depending on the distance and power of the gun you are shooting, weighing comes next.
Have a nice weekend,
AZ
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Pete Wass
Well-known member
Heat straightening:
I am an unashamed YouTube Adict. I, pretty much watch vids done by guys who do machining. There are at least two I have watched on heat straightening, one by Keith Rucker and the other by Keith Fenner of Turnwright Machine. Turnwright machine does a lot of propeller shaft work and he shows straightening a long shaft in his vid.Keith Rucker straightnes a tool arbor in the video he has posted. Got me to wondering if rifle barrels can de straightened in the same manor, using the same techniques? I have one to try when I get home. I will report.
Pete
I am an unashamed YouTube Adict. I, pretty much watch vids done by guys who do machining. There are at least two I have watched on heat straightening, one by Keith Rucker and the other by Keith Fenner of Turnwright Machine. Turnwright machine does a lot of propeller shaft work and he shows straightening a long shaft in his vid.Keith Rucker straightnes a tool arbor in the video he has posted. Got me to wondering if rifle barrels can de straightened in the same manor, using the same techniques? I have one to try when I get home. I will report.
Pete
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I don't know about that technology Pete but please provide me the YouTube link (s) and I will gladly research it for you among the industry and people I know that have authority to speak about this particular technology..It sounds feasible to me, but again, I don't have the expertise in this field and have never seen it applied to gun barrels.
Man, if you can believe it!...Second week of October and we already have winter weather in NW Montana...Lots of snow around the area, will be putting those studded tires on my pick up tomorrow and will need to winterize everything ASAP!
Best regards,
AZ
Man, if you can believe it!...Second week of October and we already have winter weather in NW Montana...Lots of snow around the area, will be putting those studded tires on my pick up tomorrow and will need to winterize everything ASAP!
Best regards,
AZ
B
Boomer_Mikey
Guest
I haven't seen a streight barrel yet...
I've machined many .177 Lothar Walther, BSA, and Lilja barrels; none of them were straight to within 0.002" and none of them were as bad as 0.020". The average runs around 0.006" to 0.008" in 25". The bore can be relatively straight but seldom on the centerline of the blank resulting in the bore shooting offset from the blank. Indexing permits us to orient the offset in a vertical plane so gravity will help dampen the vibrations to minimize dispersion. This is a good thing if you shoot at targets at multiple ranges. Shooting at one distance in the BR games doesn't make indexing as important; however, reducing group size alone is enough reason to do it and barrels change characteristics over time. It's nice to be able to re-index the barrel when you notice groups that can be improved with a small change in the orientation of the barrel; a 10% improvement in group size equals more X's
Have fun,
Boomer
I've machined many .177 Lothar Walther, BSA, and Lilja barrels; none of them were straight to within 0.002" and none of them were as bad as 0.020". The average runs around 0.006" to 0.008" in 25". The bore can be relatively straight but seldom on the centerline of the blank resulting in the bore shooting offset from the blank. Indexing permits us to orient the offset in a vertical plane so gravity will help dampen the vibrations to minimize dispersion. This is a good thing if you shoot at targets at multiple ranges. Shooting at one distance in the BR games doesn't make indexing as important; however, reducing group size alone is enough reason to do it and barrels change characteristics over time. It's nice to be able to re-index the barrel when you notice groups that can be improved with a small change in the orientation of the barrel; a 10% improvement in group size equals more X's
Have fun,
Boomer
Bore angle orientation and vibration
"Indexing permits us to orient the offset in a vertical plane so gravity will help dampen the vibrations to minimize dispersion"
Are you saying the barrel vibrates in a different plane when the bore tips vertically (6 or 12 o'clock) than when the bore is pointing elsewhere?
If so, how do you know this is true?
"Indexing permits us to orient the offset in a vertical plane so gravity will help dampen the vibrations to minimize dispersion"
Are you saying the barrel vibrates in a different plane when the bore tips vertically (6 or 12 o'clock) than when the bore is pointing elsewhere?
If so, how do you know this is true?
B
broekzwans
Guest
If the bore tips on 6 or 12 o'clock the recoil will be straight backwards with a small tip up or down, if the barrel is rotated the recoil will start directing sideways.
So far the theory, has anyone experienced the above? I think the difference in recoil direction is so small that this will be barely noticeable..
Pete Wass
Well-known member
Just type in those names
Just type in Keith Fenner heat straightening. same thing for Keith Rucker heat straightening. My only question is will SS take the heat? Don't see why not but if it works, barrels could be straightened pretty easily this way. Thinking about it, Keith Fenner is straightening SS propeller shafts sooooooo. Pretty interesting what folks learn in Shipyards and Museums full of antique machinery.
The big question for me is the concentricity of bore to O.D. If that is off, one must have a method of measuring the bore. The folks in the factories used some sort of chart on the wall to look at when they sighted through the bore. I think there may be a YouTube in the Savage factory of that.
Pete
Just type in Keith Fenner heat straightening. same thing for Keith Rucker heat straightening. My only question is will SS take the heat? Don't see why not but if it works, barrels could be straightened pretty easily this way. Thinking about it, Keith Fenner is straightening SS propeller shafts sooooooo. Pretty interesting what folks learn in Shipyards and Museums full of antique machinery.
The big question for me is the concentricity of bore to O.D. If that is off, one must have a method of measuring the bore. The folks in the factories used some sort of chart on the wall to look at when they sighted through the bore. I think there may be a YouTube in the Savage factory of that.
Pete
I believe I saw that vid somewhere along the line. Straightening a barrel- a better terminology is straightening the bore.
from the same vid:
peer down barrel at a bright area rotate barrel on the "axis of the bore" watching closely, a bore that is very crooked should/ could be observed to do 2 things while looking through it, a reduction in apparent brightness and a narrowing of the far end from your view point . This is subtle as heck unless something is way out of wack.
Also remember from my muzzle loader days a sketch or a picture of a Barrel press for straightening same, - a U shaped type press not unlike a early block printing press ( likely was, just re-purposed) beefy threaded shaft you can picture the operation.
from the same vid:
peer down barrel at a bright area rotate barrel on the "axis of the bore" watching closely, a bore that is very crooked should/ could be observed to do 2 things while looking through it, a reduction in apparent brightness and a narrowing of the far end from your view point . This is subtle as heck unless something is way out of wack.
Also remember from my muzzle loader days a sketch or a picture of a Barrel press for straightening same, - a U shaped type press not unlike a early block printing press ( likely was, just re-purposed) beefy threaded shaft you can picture the operation.
Pete:
Sorry for the long wait....I spoke long to one of our PHD Thermodynamics experts who is also an excellent shooter and smith at the lab...He basically says that it would mandatory to normalize the barrel after applying heat in any kind of heat straightening process, or the harmonics would be all screwed up given the different orientation of the steel molecules after heating different spots along the barrel...But
He adds that bore dimensions could and would be screwed up permanently given the high temps...He showed me some examples of internal dimensions in bushings, extruded tubing and even mandrel formed (hammer forging) tubing made out of chrome moly, SS, and even Nikasil and other exotic ceramic materials used in the aerospace industry and where the temperature was raised intensively at one or more points along the axis exceeding the memory or limits of the materials; normalizing the bushings at max temp didn't return them to original specs and some microscope pictures showed tight spots along the axis (rings effect)...This effect would be permanent and detrimental to any kind of accuracy.
The rest of his observations I will not post as they are not my field and too complicated...We would need to take an intensive course at NASA...Not for me, too boring...I rather shoot!
So I guess we are back to ground zero...
Regarding concentricity of bore to outer diameter: I remember Ed Shilen air gauging his drilled blanks before and then after rifling...But then he had some more optical instrumentation that I didn't see operating, I suppose that an optical comparator was used at the time and before modern Bore Lasers as the Hamar L708 series and other more sophisticated were available.
Best regards,
AZ
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J
Jonnyh
Guest
Az how can you measure these barrels without removing the barrel sleeve.
Most have induced barrel droop downwards before bonding in to barrel sleeve perhaps 1 in 2 and same for Anchutz and many others. Bore of the sleeve 15.3mm, some are like a banana within it to some extent. Some manufacturers even leave a mark top dead centre to align the barrel sleeve dovetail.
Bare barrel granted you can check for runout along its length.
Confirm heat process will alter grain structure.
There is a video some where of FX straightening barrels but checked externally by rolling not off the bore.
Must say one of the most accurate barrels ever come across in my early days 25 years ago I accidentally got a polishing rag caught subsequently bending barrel almost 90 degrees. Bit of cold straightening by eye on o/d some where near turned out repetitive groups up to 60 yards worthy of the best barrels ever made 5mm edge to edge.
Also seen Lothar Walther P800 barrels with barrel droop group exceptionally well out to 88 yards, quite a few were used in the World Champs.
Never done it myself but the idea of indexing is to see if it groups better by revolving barrel. If the droop or bend is vertical that's as good as it gets. All barrels whip upon firing you will be amased.
Jonnyh:
In the old days we used very precise adjustable rods with bronze bushings for measuring bores along the longitudinal axis, you gave it a little twist and it locked inside the bore of whatever you were measuring and you could do it at different bore lengths...Then came laser technology and that made the job a lot easier and more precise...Nowadays you can buy laser instrumentation like the Hamar 740 series and many other that are accurate to one-one and a half hundred thousands over a length of 12 inches (.00001 - 12")...With a little ingenuity you can use an optical comparator, etc...We have some interests in a major Aero-Space Lab and have access to laser and other instrumentation for measuring pretty much anything...
Long range centerfire BR shooters index their barrels at 12 o'çlock for the one and only purpose of having the max range for elevation (scope adjustment), I have seen barrels indexed at pretty much any position you can imagine and people who do it for improving accuracy, usually stay within the vertical axis as vertical groups are easier to control than horizontal ones as you mention...If on top of the bore not being straight you have the outside diameter not concentric to the bore, then your problems will aggravate quite a bit...GRANTED!, there is some precision to be gained with this indexing procedure but I am a strong advocate and lab tests have shown that nothing works better than a good barrel to start with as mentioned in previous posts in this very same thread.
Removing sleeves is a pretty simple straight forward procedure not relevant for this thread but some years back we swapped 15 mm steel sleeved barrels on FWB, Walher and Anschutz guns for certain brand of barrels that were thicker and sleeved with carbon fiber...Same overall weight but a much stronger combination less affected by vibrations. We also tested original un-sleeved barrels and the same barrels making them "Tensioned Barrels" for comparison with the factory sleeved configuration.
I have stated many times that in my perspective indexing is a procedure for making a "mediocre barrel shoot better"...By these very same parameters, a tensioned-barrel is another way of achieving the same effect, but it is also true that in theory good straight concentric barrels can benefit to some point when tensioned, and the same is true when sleeved. My reluctance to either methodology for correcting a barrel is because life is too short and I rather spend my time shooting than artificially fixing a problem that could've be avoided buying a good quality straight barrel; if the barrels don't shoot or are not straight they simply don't go on my guns...but again, that is me and I respect other opinions.
Ed Shilen was a good friend from whom I learned many things...I consider him one of the best and most knowledgeable barrel makers ever. Ed and people like him develop a very acute sense of "Straightness - Eye Measuring" and have a remarkable discriminatory keen eye...Ed would look though the bore of a barrel, rotate it and and roughly tell you if it was straight eough or not to be a good barrel. To me doing this it is near to impossible...I've heard that the owner of FX guns uses this technique and that he is good at it.
Spend your money on the best barrel you can get and don't cut corners, any stable consistent balanced platform (rest of components) will make this good barrel an excellent shooting gun...The opposite is not true, a bad barrel in the best of platforms whether you index the barrel, sleeve it, or tension it, you will always end up with a mediocre gun.
Best regards,
AZ
In the old days we used very precise adjustable rods with bronze bushings for measuring bores along the longitudinal axis, you gave it a little twist and it locked inside the bore of whatever you were measuring and you could do it at different bore lengths...Then came laser technology and that made the job a lot easier and more precise...Nowadays you can buy laser instrumentation like the Hamar 740 series and many other that are accurate to one-one and a half hundred thousands over a length of 12 inches (.00001 - 12")...With a little ingenuity you can use an optical comparator, etc...We have some interests in a major Aero-Space Lab and have access to laser and other instrumentation for measuring pretty much anything...
Long range centerfire BR shooters index their barrels at 12 o'çlock for the one and only purpose of having the max range for elevation (scope adjustment), I have seen barrels indexed at pretty much any position you can imagine and people who do it for improving accuracy, usually stay within the vertical axis as vertical groups are easier to control than horizontal ones as you mention...If on top of the bore not being straight you have the outside diameter not concentric to the bore, then your problems will aggravate quite a bit...GRANTED!, there is some precision to be gained with this indexing procedure but I am a strong advocate and lab tests have shown that nothing works better than a good barrel to start with as mentioned in previous posts in this very same thread.
Removing sleeves is a pretty simple straight forward procedure not relevant for this thread but some years back we swapped 15 mm steel sleeved barrels on FWB, Walher and Anschutz guns for certain brand of barrels that were thicker and sleeved with carbon fiber...Same overall weight but a much stronger combination less affected by vibrations. We also tested original un-sleeved barrels and the same barrels making them "Tensioned Barrels" for comparison with the factory sleeved configuration.
I have stated many times that in my perspective indexing is a procedure for making a "mediocre barrel shoot better"...By these very same parameters, a tensioned-barrel is another way of achieving the same effect, but it is also true that in theory good straight concentric barrels can benefit to some point when tensioned, and the same is true when sleeved. My reluctance to either methodology for correcting a barrel is because life is too short and I rather spend my time shooting than artificially fixing a problem that could've be avoided buying a good quality straight barrel; if the barrels don't shoot or are not straight they simply don't go on my guns...but again, that is me and I respect other opinions.
Ed Shilen was a good friend from whom I learned many things...I consider him one of the best and most knowledgeable barrel makers ever. Ed and people like him develop a very acute sense of "Straightness - Eye Measuring" and have a remarkable discriminatory keen eye...Ed would look though the bore of a barrel, rotate it and and roughly tell you if it was straight eough or not to be a good barrel. To me doing this it is near to impossible...I've heard that the owner of FX guns uses this technique and that he is good at it.
Spend your money on the best barrel you can get and don't cut corners, any stable consistent balanced platform (rest of components) will make this good barrel an excellent shooting gun...The opposite is not true, a bad barrel in the best of platforms whether you index the barrel, sleeve it, or tension it, you will always end up with a mediocre gun.
Best regards,
AZ
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B
Boomer_Mikey
Guest
If we took a survey ...
the results would indicate that most of the top guns in use by the top shooters in Air Rifle Benchrest have barrels that are indexed; that should be proof enough that there is something to it...
Guns that don't require a side port in the barrel are the easiest to work with only requiring a nice crown, leade and chamber cut in them to make them the best they can be.
Guns with a side ported barrel require more work; however, my experience has been that a side ported gun can be just as capable when a good crown, thimble fitted with care to support the pellet used with a nice leade that rotates in the action true to the bore.
If you shoot enough groups indoors, they will show you the direction the centerline of the bore is indexed to as long as you have a good crown. Index position may change slightly with a change in pellet size/weight/speed/brand and other factors, such as stock, airtube and barrel pressure points, extreme temperature, etc.
Some of the best shooters I know keep records of groups shot, velocity and extreme spreads of each pellet lot number for each barrel along with notes about the cleaning method that produces the best "X" count and how many shots are required for each barrel to return to a best accuracy state after cleaning too. With such data one can tell what is normal when things go haywire.
Have fun,
Boomer
the results would indicate that most of the top guns in use by the top shooters in Air Rifle Benchrest have barrels that are indexed; that should be proof enough that there is something to it...
Guns that don't require a side port in the barrel are the easiest to work with only requiring a nice crown, leade and chamber cut in them to make them the best they can be.
Guns with a side ported barrel require more work; however, my experience has been that a side ported gun can be just as capable when a good crown, thimble fitted with care to support the pellet used with a nice leade that rotates in the action true to the bore.
If you shoot enough groups indoors, they will show you the direction the centerline of the bore is indexed to as long as you have a good crown. Index position may change slightly with a change in pellet size/weight/speed/brand and other factors, such as stock, airtube and barrel pressure points, extreme temperature, etc.
Some of the best shooters I know keep records of groups shot, velocity and extreme spreads of each pellet lot number for each barrel along with notes about the cleaning method that produces the best "X" count and how many shots are required for each barrel to return to a best accuracy state after cleaning too. With such data one can tell what is normal when things go haywire.
Have fun,
Boomer
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