I have my barrel indexed but did not think about the barrel twisting when tightened down so I will look into that. Thanks for the vid and the other things you do for our sport/sickness/addiction. ;^)
I began indexing airgun barrels decades ago, when it was generally much more difficult to accomplish. But the REASON for indexing back then was to change the harmonics of the barrel improve accuracy, and not so much to change relative point of impact. Now the harmonics issue is a ticklish one, since many barrels don't respond with improved accuracy ... but some DO! Even when accuracy does improve, its generally not a huge improvement that seems well worth it to most regular airgun owners.
I have indexed literally hundreds of barrels, and see some that improve shot precision as much as 1/4", or on rare occasion, maybe a bit more, but more often, there is not a significant difference (significant difference in scientific parlance means not scientifically repeatable, or in other words not out of the normal distribution).
But I DO continue to index most new barrels I install, and because even relatively tiny improvements in accuracy are important for me in the match guns I play with. A gun that shoots consistent 50 yard groups of around 1/2" to 9/16" that improves 1/16" or better is good for me, and one that shoots 1/8" better is a real Gem that might enable me to shoot better scores.
I know for a fact that some barrels are not bored perfectly concentric the the outside diameter, and therefore have some areas with thicker walls on one side than the other. Its for this reason that harmonics vary as the barrel is rotated, since the effect of gravity, and that of recoil impulse of firing can, and does change depending on barrel orientation IF the barrel is not precisely symmetrical inside and out. Even a barrel that has a bend in it, or one that DID have a bend that was straightened will be a bit stiffer in one axis than another ... and will likely vibrate with a different frequency and amplitude in axis.
I have found a barrel that is perfectly straight ( I prefer to straighten new ones so the exterior is straight, though I realize most barrel makers try to straighten by looking up the bore) that shoots to differing poi as its indexed usually shoots best (tight groups) with the lowest poi position, though sometimes its the highest position, or a push. Since I have really tested so many barrels, I now generally just index to find the lowest point and thats that .. but its not about centering the impact to the scope crosshair, but but for tighter grouping.
Wouldn't it be liner index? Cause fx called them liners, not barrels. You actually turn the liners around, not the actual barrel selves.
I began indexing airgun barrels decades ago, when it was generally much more difficult to accomplish. But the REASON for indexing back then was to change the harmonics of the barrel improve accuracy, and not so much to change relative point of impact. Now the harmonics issue is a ticklish one, since many barrels don't respond with improved accuracy ... but some DO! Even when accuracy does improve, its generally not a huge improvement that seems well worth it to most regular airgun owners.
I have indexed literally hundreds of barrels, and see some that improve shot precision as much as 1/4", or on rare occasion, maybe a bit more, but more often, there is not a significant difference (significant difference in scientific parlance means not scientifically repeatable, or in other words not out of the normal distribution).
But I DO continue to index most new barrels I install, and because even relatively tiny improvements in accuracy are important for me in the match guns I play with. A gun that shoots consistent 50 yard groups of around 1/2" to 9/16" that improves 1/16" or better is good for me, and one that shoots 1/8" better is a real Gem that might enable me to shoot better scores.
I know for a fact that some barrels are not bored perfectly concentric the the outside diameter, and therefore have some areas with thicker walls on one side than the other. Its for this reason that harmonics vary as the barrel is rotated, since the effect of gravity, and that of recoil impulse of firing can, and does change depending on barrel orientation IF the barrel is not precisely symmetrical inside and out. Even a barrel that has a bend in it, or one that DID have a bend that was straightened will be a bit stiffer in one axis than another ... and will likely vibrate with a different frequency and amplitude in axis.
I have found a barrel that is perfectly straight ( I prefer to straighten new ones so the exterior is straight, though I realize most barrel makers try to straighten by looking up the bore) that shoots to differing poi as its indexed usually shoots best (tight groups) with the lowest poi position, though sometimes its the highest position, or a push. Since I have really tested so many barrels, I now generally just index to find the lowest point and thats that .. but its not about centering the impact to the scope crosshair, but but for tighter grouping.
If i were to choose my indexing position based on group size, it would probably be my 3 o'clock position (which is the upper right group in the picture).
The STX barrels only allows indexing to a certain point. There's no way to index it exactly (yet). Plus, unless you use a torque wrench, the pressure/harmonics you apply to the liner could be different.
I'd like to see FX add a few simple things to make indexing easier.
- Add a tiny grub screw somewhere on the sleeve (or barrel, whatever they call it)
- Add a few (maybe 8) tiny indents on the liner for the grub screw to hold it in place. They could even be numbered so that you could look through the grub screw hole to view the #.
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I began indexing airgun barrels decades ago, when it was generally much more difficult to accomplish. But the REASON for indexing back then was to change the harmonics of the barrel improve accuracy, and not so much to change relative point of impact. Now the harmonics issue is a ticklish one, since many barrels don't respond with improved accuracy ... but some DO! Even when accuracy does improve, its generally not a huge improvement that seems well worth it to most regular airgun owners.
I have indexed literally hundreds of barrels, and see some that improve shot precision as much as 1/4", or on rare occasion, maybe a bit more, but more often, there is not a significant difference (significant difference in scientific parlance means not scientifically repeatable, or in other words not out of the normal distribution).
But I DO continue to index most new barrels I install, and because even relatively tiny improvements in accuracy are important for me in the match guns I play with. A gun that shoots consistent 50 yard groups of around 1/2" to 9/16" that improves 1/16" or better is good for me, and one that shoots 1/8" better is a real Gem that might enable me to shoot better scores.
I know for a fact that some barrels are not bored perfectly concentric the the outside diameter, and therefore have some areas with thicker walls on one side than the other. Its for this reason that harmonics vary as the barrel is rotated, since the effect of gravity, and that of recoil impulse of firing can, and does change depending on barrel orientation IF the barrel is not precisely symmetrical inside and out. Even a barrel that has a bend in it, or one that DID have a bend that was straightened will be a bit stiffer in one axis than another ... and will likely vibrate with a different frequency and amplitude in axis.
I have found a barrel that is perfectly straight ( I prefer to straighten new ones so the exterior is straight, though I realize most barrel makers try to straighten by looking up the bore) that shoots to differing poi as its indexed usually shoots best (tight groups) with the lowest poi position, though sometimes its the highest position, or a push. Since I have really tested so many barrels, I now generally just index to find the lowest point and thats that .. but its not about centering the impact to the scope crosshair, but but for tighter grouping.
If i were to choose my indexing position based on group size, it would probably be my 3 o'clock position (which is the upper right group in the picture).
The STX barrels only allows indexing to a certain point. There's no way to index it exactly (yet). Plus, unless you use a torque wrench, the pressure/harmonics you apply to the liner could be different.
I'd like to see FX add a few simple things to make indexing easier.
- Add a tiny grub screw somewhere on the sleeve (or barrel, whatever they call it)
- Add a few (maybe 8) tiny indents on the liner for the grub screw to hold it in place. They could even be numbered so that you could look through the grub screw hole to view the #.
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Grub screw idea is good, or even a lightly springed ball detent like what’s on a ratchet on the outer sleeve to catch those indents on the STX liner. Just something to hold it in place as you tighten up the lock nut.