Tuner?
Posted: Tue Dec 16, 2014 10:18 am
I recently sent Danny some thoughts about tuners he requested. Seeing I have had a few people ask me about them, I decided to post some information again for others who may be interested and added a bit to comments I gave to Danny. People may have different ideas and they are welcome to contribute their experiences. You don’t need a tuner if you get load development right but they can assist in other situations.
There is a vibration moment as the bullet leaves the muzzle and that is why I have the effective weight of my tuner past the muzzle rather than just a weight on the muzzle. I prefer a variable tuner. Some of this discussion has been had before in relation to a fundamental weight that counters fundamental barrel movement and a lighter weight which acts on barrel pulses. So I don’t intend to elaborate on these characteristics in any detail. If you have a heavy profile barrel, the tuner weight tends to be heavier.
Remarks to Danny.
Making the tuner out of stainless is fine. If you can’t thread your barrel to attach a tuner directly, (so you can clean your muzzle/crown), have someone slip on a threaded band (sleeve) and “Locktight” it in place to receive the inner tube of the tuner. Make sure it is flush with the muzzle. Any loose tuner is bad news. Also make sure the internal section or tube butts up hard against the end of the muzzle, so that the desired internal diameter starts immediately from the muzzle. For a projectile of .243” (6 mm) this diameter is about .7”. For a projectile say .308”, the internal diameter is about .86” and in the case of your old tuner .88” which is fine for 30 calibre. You can always run with .7 for your Dasher and if not right, you can open it up. For others who use 7mm I calculated the bore diameter to be about .79” for the tuner inner tube. For .223, about .62”. I put a neoprene washer under the lip of the thimble, to make sure the thimble is vibration free. I also put a grub screw in the thimble to lock it in place as well.
Sometimes the weight of the tuner you are going to make is not sufficient to make it a fundamental weight, for fundamental lift tuning. You can try to induce about an 80 fps difference in test rounds with different loads and try and hit the same spot at twenty five yards by altering barrel lift by adding weights to a thin aluminium bloop tube to come up with a fundamental weight. Then you go about making a thimble to replace the weights you added of the same weight to allow for fine adjustment later. If you are getting one hole with little additional weight, then load development without a tuner will be enough. If its a tad enlarged, then you will only need a light tuner.
Its another ball game if you can’t make the shots impact in a suitable position at twenty five yards i.e. with slow bullets impacting on top of fast bullets for a positive compensation tune or about the same elevation for a neutral tune. This is often the case with heavy profile short barrels. So take your testing distance to 140 yards using loads you would for normal load development. It doesn’t really matter because you can still work on secondary and tertiary vibrations with a lighter tuner and not worry about a fundamental weight. But the exact weight involves a bit of guess work. The lighter weight with a variable external thimble acting on secondary and tertiary pulses can still tune for group shape before or about a node in relation to either a nodal tune, an OCW tune or a positive compensation tune – whatever your poison. Anywhere between 2 - 6 ounces is fine. Its a bit of suck it and see, so make a few thimbles of varying weight up and see how responsive your gear is to varying each thimble. Any weight will act as a damper and possibly extend that node if you are a nodal tuner. But I really hunt for an OCW tune about a positive peak where possible.
On my wife’s rifle I have gone for an inner tube made of aluminium so that the actual thimble of the tuner which is made of brass (1” long x ¼” deep), moves forward and aft along a thread. It happens to work best with the thimble weight balance just past the muzzle. You could make this thimble deeper for more weight on a heavy profile barrel, not a light one like hers. You can make your internal tuner tube longer to gain leverage if you think the weight is insufficient. The purpose of this design is to focus the weight on the thimble and not the internal tube which it moves along. It makes the barrel a little more responsive to change. Similar to the Beggs tuner which has two (approximately) ¼ “ x 1 ½ “ disks locked together covering half an inch of inner support tube therefore focussing the weight on a narrow section of the tuner rather than on a long length. This is working on a leverage principle rather than a total weight principle to equalize forces such as used with just a large weight on the muzzle as a damper.
Basic Tuning
It really does not take much distance to move a tuner between nodal pulses. The worst thing you can do is try and chase shots with a tuner. Its setting is fixed and based on predetermined tests like I do in laying out load development plots in the horizontal as I have done with Tony on a previous thread. A lot of people don’t realize that in using a tuner they are actually moving from a peak to a trough node if they go far enough. There is confusion between what the consider to be an upper node. I think they are really meaning the next node. So any direction, forward or back you actually move between a node. My preference is for the positive peak so I like to skip the next node because it is a trough and go to the next one again knowing it will be a peak. If I am getting too much vertical I move the tuner out, to make it harder for the barrel to be whipped up too far, and if I am getting lateral, I move the tuner in. But this is basic use.
In advanced tuning, I tune the rifle without the tuner in place for my best tune, keeping a track horizontally in a round robin test of vertical spreads. I then attach the tuner, and with further testing of the selected load, move the tuner to hit the same spot as my best load in elevation. I then fiddle fore and aft altering it changing the group shape with a bit of vertical in it to maximise the compensation tune I had already established.
This is not a nodal tune, which you can work up with load development with the tuner in place from the beginning which is most effective from 300 to 700 yards.
I then lock my tuner in place and don’t touch it unless there is a clear change in atmospheric density. Then I only move the tuner 1/3 to ½ turn at best because there is usually something else responsible for errant groups.
A major purpose of my method is to have the tuner respond to conditions as if I was making a change in powder based on past testing and experience in changed conditions. For example in the old days, the tune difference between Gippsland and Bendigo was in the order of .6 grain in .308. In other words 46 grains of 2208 for Bendigo with a lower atmospheric density to 46.3/46.6 for various Gippsland ranges with higher atmospheric density. The other major purpose is of course to maintain a group shape that is less sensitive to the wind with that element of vertical in it, but not too much to tip you out.
If you were really serious about a Queens etc, you would conduct tuning at the venue and not try and second guess it, unless you have vast experience. A tuner is not for a beginner, as you have to understand the theory behind its movements for various tune methods such as a nodal tune, an OCW tune and a compensation tune and at what distances and in what atmospheric conditions it is appropriate to use each method of tune.
Only with testing do I make larger changes with my tuner to cater for a change in mound angle which will change bore angle at long range. I do this testing by altering the height of my aiming point at short range to mimic mound angle changes that I can expect at different ranges. You need to keep records of mound to target angles on different ranges if you want to go down this path. Its a bit over the top but doable.
So the normal length of your inner tube does not have to be that long, but I would be going with a minimum of 1.5 inches past the muzzle even though the thimble weight close to the muzzle often works best. But if you want to accommodate more leverage to cover mound changes then you could run to 4 inches. It is far easier to adjust your front rest head angle like Alan and I have for mound changes (but really only for long range compensation tuning).
When I first test with my tuner on, I place the rear of the thimble where the muzzle ends and move forward from there. Because the barrel moves up and down you will find a spot that suits because the patterns tend to be rhythmic.
You do not want a tuner that makes the balance too front heavy. Lighter but longer inner tube will work. But you can keep making the tuner heavier to maximise rifle weight, but only if the balance is right and assuming you have not gone past the fundamental weight for a tuner. On the other hand you may want a light tuner to maximise barrel lift for a compensation tune but where it can influence group shape to make your gear less wind sensitive or in the case of a compensation tune allow slow bullets to impact higher than fast bullets. So the best tuners are really custom tuners. This development takes a lot of time. So if you have a campaign in mind for a set event, you have to work up to it and prior planning prevents piss poor performance. Otherwise set and forget your tuner based on the best group shape from your round robin testing.
I don’t use marks for reference, because you find your sweet spot first. I use the grub screw as the reference point and go in 1/3 to ½ turns or weeny bits knowing a full turn only moves you .004” anyway depending on your thread pitch. The pressures on bullet exit are immense and you don’t see fighter jet planes with big wings, so only a small about of trim is necessary about the sweet spot.
Hope this can help you Danny.
There is a vibration moment as the bullet leaves the muzzle and that is why I have the effective weight of my tuner past the muzzle rather than just a weight on the muzzle. I prefer a variable tuner. Some of this discussion has been had before in relation to a fundamental weight that counters fundamental barrel movement and a lighter weight which acts on barrel pulses. So I don’t intend to elaborate on these characteristics in any detail. If you have a heavy profile barrel, the tuner weight tends to be heavier.
Remarks to Danny.
Making the tuner out of stainless is fine. If you can’t thread your barrel to attach a tuner directly, (so you can clean your muzzle/crown), have someone slip on a threaded band (sleeve) and “Locktight” it in place to receive the inner tube of the tuner. Make sure it is flush with the muzzle. Any loose tuner is bad news. Also make sure the internal section or tube butts up hard against the end of the muzzle, so that the desired internal diameter starts immediately from the muzzle. For a projectile of .243” (6 mm) this diameter is about .7”. For a projectile say .308”, the internal diameter is about .86” and in the case of your old tuner .88” which is fine for 30 calibre. You can always run with .7 for your Dasher and if not right, you can open it up. For others who use 7mm I calculated the bore diameter to be about .79” for the tuner inner tube. For .223, about .62”. I put a neoprene washer under the lip of the thimble, to make sure the thimble is vibration free. I also put a grub screw in the thimble to lock it in place as well.
Sometimes the weight of the tuner you are going to make is not sufficient to make it a fundamental weight, for fundamental lift tuning. You can try to induce about an 80 fps difference in test rounds with different loads and try and hit the same spot at twenty five yards by altering barrel lift by adding weights to a thin aluminium bloop tube to come up with a fundamental weight. Then you go about making a thimble to replace the weights you added of the same weight to allow for fine adjustment later. If you are getting one hole with little additional weight, then load development without a tuner will be enough. If its a tad enlarged, then you will only need a light tuner.
Its another ball game if you can’t make the shots impact in a suitable position at twenty five yards i.e. with slow bullets impacting on top of fast bullets for a positive compensation tune or about the same elevation for a neutral tune. This is often the case with heavy profile short barrels. So take your testing distance to 140 yards using loads you would for normal load development. It doesn’t really matter because you can still work on secondary and tertiary vibrations with a lighter tuner and not worry about a fundamental weight. But the exact weight involves a bit of guess work. The lighter weight with a variable external thimble acting on secondary and tertiary pulses can still tune for group shape before or about a node in relation to either a nodal tune, an OCW tune or a positive compensation tune – whatever your poison. Anywhere between 2 - 6 ounces is fine. Its a bit of suck it and see, so make a few thimbles of varying weight up and see how responsive your gear is to varying each thimble. Any weight will act as a damper and possibly extend that node if you are a nodal tuner. But I really hunt for an OCW tune about a positive peak where possible.
On my wife’s rifle I have gone for an inner tube made of aluminium so that the actual thimble of the tuner which is made of brass (1” long x ¼” deep), moves forward and aft along a thread. It happens to work best with the thimble weight balance just past the muzzle. You could make this thimble deeper for more weight on a heavy profile barrel, not a light one like hers. You can make your internal tuner tube longer to gain leverage if you think the weight is insufficient. The purpose of this design is to focus the weight on the thimble and not the internal tube which it moves along. It makes the barrel a little more responsive to change. Similar to the Beggs tuner which has two (approximately) ¼ “ x 1 ½ “ disks locked together covering half an inch of inner support tube therefore focussing the weight on a narrow section of the tuner rather than on a long length. This is working on a leverage principle rather than a total weight principle to equalize forces such as used with just a large weight on the muzzle as a damper.
Basic Tuning
It really does not take much distance to move a tuner between nodal pulses. The worst thing you can do is try and chase shots with a tuner. Its setting is fixed and based on predetermined tests like I do in laying out load development plots in the horizontal as I have done with Tony on a previous thread. A lot of people don’t realize that in using a tuner they are actually moving from a peak to a trough node if they go far enough. There is confusion between what the consider to be an upper node. I think they are really meaning the next node. So any direction, forward or back you actually move between a node. My preference is for the positive peak so I like to skip the next node because it is a trough and go to the next one again knowing it will be a peak. If I am getting too much vertical I move the tuner out, to make it harder for the barrel to be whipped up too far, and if I am getting lateral, I move the tuner in. But this is basic use.
In advanced tuning, I tune the rifle without the tuner in place for my best tune, keeping a track horizontally in a round robin test of vertical spreads. I then attach the tuner, and with further testing of the selected load, move the tuner to hit the same spot as my best load in elevation. I then fiddle fore and aft altering it changing the group shape with a bit of vertical in it to maximise the compensation tune I had already established.
This is not a nodal tune, which you can work up with load development with the tuner in place from the beginning which is most effective from 300 to 700 yards.
I then lock my tuner in place and don’t touch it unless there is a clear change in atmospheric density. Then I only move the tuner 1/3 to ½ turn at best because there is usually something else responsible for errant groups.
A major purpose of my method is to have the tuner respond to conditions as if I was making a change in powder based on past testing and experience in changed conditions. For example in the old days, the tune difference between Gippsland and Bendigo was in the order of .6 grain in .308. In other words 46 grains of 2208 for Bendigo with a lower atmospheric density to 46.3/46.6 for various Gippsland ranges with higher atmospheric density. The other major purpose is of course to maintain a group shape that is less sensitive to the wind with that element of vertical in it, but not too much to tip you out.
If you were really serious about a Queens etc, you would conduct tuning at the venue and not try and second guess it, unless you have vast experience. A tuner is not for a beginner, as you have to understand the theory behind its movements for various tune methods such as a nodal tune, an OCW tune and a compensation tune and at what distances and in what atmospheric conditions it is appropriate to use each method of tune.
Only with testing do I make larger changes with my tuner to cater for a change in mound angle which will change bore angle at long range. I do this testing by altering the height of my aiming point at short range to mimic mound angle changes that I can expect at different ranges. You need to keep records of mound to target angles on different ranges if you want to go down this path. Its a bit over the top but doable.
So the normal length of your inner tube does not have to be that long, but I would be going with a minimum of 1.5 inches past the muzzle even though the thimble weight close to the muzzle often works best. But if you want to accommodate more leverage to cover mound changes then you could run to 4 inches. It is far easier to adjust your front rest head angle like Alan and I have for mound changes (but really only for long range compensation tuning).
When I first test with my tuner on, I place the rear of the thimble where the muzzle ends and move forward from there. Because the barrel moves up and down you will find a spot that suits because the patterns tend to be rhythmic.
You do not want a tuner that makes the balance too front heavy. Lighter but longer inner tube will work. But you can keep making the tuner heavier to maximise rifle weight, but only if the balance is right and assuming you have not gone past the fundamental weight for a tuner. On the other hand you may want a light tuner to maximise barrel lift for a compensation tune but where it can influence group shape to make your gear less wind sensitive or in the case of a compensation tune allow slow bullets to impact higher than fast bullets. So the best tuners are really custom tuners. This development takes a lot of time. So if you have a campaign in mind for a set event, you have to work up to it and prior planning prevents piss poor performance. Otherwise set and forget your tuner based on the best group shape from your round robin testing.
I don’t use marks for reference, because you find your sweet spot first. I use the grub screw as the reference point and go in 1/3 to ½ turns or weeny bits knowing a full turn only moves you .004” anyway depending on your thread pitch. The pressures on bullet exit are immense and you don’t see fighter jet planes with big wings, so only a small about of trim is necessary about the sweet spot.
Hope this can help you Danny.
Can you get them in plain green? David.
. 
David.
Maybe the minor merits of this, together with the Obermyer tube which is said to, in addition, condition the atmosphere, assists with bullet stability.
