Positive compensation or stopped muzzle, a more low tech test.

D

Dennis D.

Member
On a couple of other forums I have been reading the debates between the two camps and have found it extremely interesting and entertaining. Now being of a low tech mind kind of guy I have come up with an old fashion type of test. I do not have the facility or the "killer" rifle to do the test, that is a rifle that will shoot .200 groups or less all day every day and a 200 yard indoor range but somewhere someone might.

So, if the muzzle is "stopped" then at 200 yards the difference in drop between ammo at 1085fps and ammo at 1035fps should be 4 inches if the ballistics calculator I used is correct, using a BC of .150. Under no circumstances should there be vertical spread of the two different speeds of ammo of less than that possible unless there is an error in the ballistic calculator. I understand that there are inconsistencies in ammo however one should still come out with a very elongated group of around 4 inches high and an inch wide. Round groups should be totally out of the question. Also if the muzzle is truly stopped this must be the absolute maximum accuracy setting at both 50 yards and 200 yards for the theory to work, no readjusting of the muzzle device should make it any better.

The test for " positive compensation" of course is if the muzzle device can be changed to be able to shoot a round group. If that happens then some sort of movement must be happening causing the slower bullets to hit higher on the target falling into the same group as the faster bullets. Now whether this is movement of the muzzle, change in departure angle of some other type of movement is for folks more clever than I to discern.

Anyone got stuff to actually do the test?

Dennis
 
I don't think you have read enough about the two "camps". One theory states that compensation comes by way of the barrel flexing in front of the node (dead spot) therefore sending the slower bullet on a higher trajectory. The other camp believes the muzzle is stopped, in other words the node is at the crown and the barrel is flexing behind this point and causing the slower bullet to be sent on a higher trajectory. Who gives a $%#@?
 
Dennis, the PA version of one particular theory has stated that at a substantial varience from a 50 yard tune requires an entirely differnt tune. I'd hate to try and tune a .22 at 200. Shooting some indoors with the subtle mirage, temp variences, cross drafts, etc, etc, I'd imagine 200 yards is challanging.
 
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CliffA said:
I don't think you have read enough about the two "camps". One theory states that compensation comes by way of the barrel flexing in front of the node (dead spot) therefore sending the slower bullet on a higher trajectory. The other camp believes the muzzle is stopped, in other words the node is at the crown and the barrel is flexing behind this point and causing the slower bullet to be sent on a higher trajectory. Who gives a $%#@?
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I'll simply repeat part of your post back to you.
I don't think you have read enough about the two "camps".
Since you have completely misrepresented the "camp" I'm firmly entrenched into.
I hold that the node is still best when located at the crown, but the muzzle is not "Stopped" in the sense that the other camp holds - IE that it is motionless and always at the same angle. My working theory on the tuner effect is that the transverse motion is at a minimum, but the angular rate of change in position can be matched to the requirements of making a slower shot travel a higher trajectory than a faster one - resulting in reduced vertical dispersion at a given downrange target distance.

And in answer to your last question
CliffA said:
Who gives a $%#@?
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Apparently quite a few folks. If you don't happen to be one of those folks, that's fine. No one is requiring anyone to read the progress (or lack thereof in some cases) being cussed and/or discussed.
 
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CliffA, actually the stopped muzzle camp as proposed by Bill Calfee states that the muzzle is at a dead stop and that the node has a straight flat section at the muzzle that he calls the "parallel node". You can find his drawings in the Precision Shooting articles he did, in his book and on the Rimfire Accuracy web site. As I understand his explanation the muzzle is at a complete and total stand still pointing straight ahead and the rest of the barrel behind it is flexing. As Vibe has stated "positive compensation" still believes that the muzzle is at the node so that is is not moving up and down significantly, however the angle of the muzzle is changing. And if you don't give a hoot that's okay, there are plenty of other threads to read.

Tim, exactly, if you have to retune for 200 yards then there must be some kind of movement going on that requires co-ordination of the timing of slower velocity bullets with those at a higher velocity. We have regular 200 yard .22 matches at our club so I do have some idea of the difficulty of shooting at that distance but I'm guessing the subtle variations of an indoor range are easier to deal with than a swirling 15 mph wind that blows up the canyon our range is in.

Dennis
 
Vibe is correct. The muzzle is not stopped. PERIOD. As to shooting at 50 or 200 yards has no bearing on tuning. IF the muzzle is stopped as someone claims, it is stopped if you shoot and at any distance. Sopped is Stopped. I shoot in rim fire competitions from 50 to 200 yards and never change the setting. Why would you. When your rifle is tuned it is tuned. For one extremely fleeting moment, the movement actually DOES stop before it starts moving in the other direction. Just as if you threw any object straight up into the air, there is a very brief moment in time when the object comes to a stop before gravity brings it back down.

And yes, tuners do improve accuracy. Would never debate that.

Science proves things. Opinions prove nothing.
 
Good, then if you believe in the science as I do then you know that a rifle tuned for 50 yards is NOT tuned for 100 or 200 yards. And that is my point, if the tune changes from yardage to yardage there must be some sort of compensating mechanism at work. If you want to see the numbers go to Varmint Al's site as he has done a huge amount of work and shows just that.

Dennis
 
Read varmint Al's many times. When you tune a barrel according a certain gentleman theory, the muzzle is stopped. So does the muzzle start to move if you shoot from 50 to 200 yards?

And I have a ton of experience shooting the same rimfire rifle from 50-100-200- -400 yards and I never change tuner settings.
 
shooter65 said:
Read varmint Al's many times. When you tune a barrel according a certain gentleman theory, the muzzle is stopped. So does the muzzle start to move if you shoot from 50 to 200 yards?

And I have a ton of experience shooting the same rimfire rifle from 50-100-200- -400 yards and I never change tuner settings.
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So at what point does the vertical due to velocity variation start to become an issue again? The OP took the most common spread of some good ammo (I think) and reported that 4" of vertical at 200 yards would be about the absolute best one could hope for, and that round shaped groups out at that range would be pretty much impossible.
With properly managed "compensation" I think that can be bettered by quite a bit. But not with the current style of tuner design.
 
Vibe said:
So at what point does the vertical due to velocity variation start to become an issue again? The OP took the most common spread of some good ammo (I think) and reported that 4" of vertical at 200 yards would be about the absolute best one could hope for, and that round shaped groups out at that range would be pretty much impossible.
With properly managed "compensation" I think that can be bettered by quite a bit. But not with the current style of tuner design.
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Have never witnessed it with my rifle. Tuned is tuned. Period. Wind is the big factor at 200 yards plus.
I have shot and have saw others shot some pretty impressive groups at 200 yards.

Approx. 25 moa to 200 yards using match ammo. Read the wind from there. K.I.S.S. !

http://www.rimfireaccuracy.com/Forums/showthread.php/1911-Pics-from-our-200-yard-prone-match
 
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shooter65 said:
Read varmint Al's many times. When you tune a barrel according a certain gentleman theory, the muzzle is stopped. So does the muzzle start to move if you shoot from 50 to 200 yards?

And I have a ton of experience shooting the same rimfire rifle from 50-100-200- -400 yards and I never change tuner settings.
Click to expand...

The following is from Al's website. I don't mean this to be confrontational, but what part of this don't you understand? For the ballistic assumptions of Al's calculations, if your rifle is perfectly tuned for 50 yards, it will out of tune by 0.33" at 100 yards. This will be difficult to see with a 25 moa rifle (I assume this was a typo:D).

Cheers,
Keith

Trajectory 22LR 50&100.jpg

TUNING & DISTANCE.... Here is a chart that shows the 100 yard trajectory of a 22LR 40 gr bullets with a BC of 0.128 and an average muzzle velocity of 1050 fps. It is assumed that the actual velocity varies from 1040 to 1060 fps with the vertical tuned out. The first case (bottom curves) is where the vertical is tuned out at 50 yards. In this case the vertical at 100 yards is 7.79-7.46 or 0.33”. The rifle is not in tune for 100 yards.

In the second case the vertical is tuned out at 100 yards. But in this case the vertical at 50 yards is 3.89-3.73 or 0.16”.
Anyone can calculate this for their rifle & ammo using free ballistic software. For small variations is muzzle velocity a 22LR rifle in tune at 50 yards is NOT in tune at 100 yards.

LAUNCH ANGLE & DROP.... For the 1040 fps and 1060 fps bullets to strike at the same elevation at the 100 yard target, the launch angle for the 1040 fps bullet has to be elevated 0.2218 degrees above that of the 1060 fps bullet. If the muzzle were somehow fixed in space so that both bullets were launched at exactly the same angle, then the 1040 fps bullet would strike the 100 yard target 0.40" lower than the 1060 fps bullet. It is not rocket science that the slower bullet will drop more in traveling to the target.

Vibe,
I am amazed at your patience. Keep up the good work.:)

Keith
 
mks said:
The following is from Al's website. I don't mean this to be confrontational, but what part of this don't you understand? For the ballistic assumptions of Al's calculations, if your rifle is perfectly tuned for 50 yards, it will out of tune by 0.33" at 100 yards. This will be difficult to see with a 25 moa rifle (I assume this was a typo:D).

Cheers,
Keith

View attachment 11993

TUNING & DISTANCE.... Here is a chart that shows the 100 yard trajectory of a 22LR 40 gr bullets with a BC of 0.128 and an average muzzle velocity of 1050 fps. It is assumed that the actual velocity varies from 1040 to 1060 fps with the vertical tuned out. The first case (bottom curves) is where the vertical is tuned out at 50 yards. In this case the vertical at 100 yards is 7.79-7.46 or 0.33”. The rifle is not in tune for 100 yards.

In the second case the vertical is tuned out at 100 yards. But in this case the vertical at 50 yards is 3.89-3.73 or 0.16”.
Anyone can calculate this for their rifle & ammo using free ballistic software. For small variations is muzzle velocity a 22LR rifle in tune at 50 yards is NOT in tune at 100 yards.

LAUNCH ANGLE & DROP.... For the 1040 fps and 1060 fps bullets to strike at the same elevation at the 100 yard target, the launch angle for the 1040 fps bullet has to be elevated 0.2218 degrees above that of the 1060 fps bullet. If the muzzle were somehow fixed in space so that both bullets were launched at exactly the same angle, then the 1040 fps bullet would strike the 100 yard target 0.40" lower than the 1060 fps bullet. It is not rocket science that the slower bullet will drop more in traveling to the target.

Vibe,
I am amazed at your patience. Keep up the good work.:)

Keith
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Part of the problem at 100 yards and over is that 1/3 to 1/2" would get lost in all the other noise. So a lot of shooters don't care, or are completely satisfied with it.
 
Sorry to be away from the conversation for so long but no internet at the house so I had to stop in at the office on the way home from this mornings duck hunt. My point exactly Keith, by 200 yards the difference becomes noticeable enough to be seen if the wind is calm enough, particularly if you are using two different speeds of ammo while testing. By using the tuner to get both speeds hitting as closely as possible to each other, which is a smaller vertical spread than the difference between the two speeds should produce according to the ballistic charts there has to be some sort of compensation going on which means that something at the muzzle end of the gun has to be moving.

Dennis
 
With a 50 yard zero it takes 25 moa of elevation to reach 200 yards with my rifle. A tuned barrel is a tuned barrel regardless of the distance you are shooting.

When I shoot with the same rifle / ammo combo it takes a total of 48 moa of elevation with the Bushnell 6500 4.5-30x50 scope set on 4.5 power and using the last mildot. In light winds, hits at 400 yards were very consistent. Shooting anything from steel to stones.

5mildots from center at 4.5X would be ~11.2mil which equals ~ 38moa + 48moa = ~86moa ~30FT of drop




mks said:
The following is from Al's website. I don't mean this to be confrontational, but what part of this don't you understand? For the ballistic assumptions of Al's calculations, if your rifle is perfectly tuned for 50 yards, it will out of tune by 0.33" at 100 yards. This will be difficult to see with a 25 moa rifle (I assume this was a typo:D).

Cheers,
Keith

View attachment 11993

TUNING & DISTANCE.... Here is a chart that shows the 100 yard trajectory of a 22LR 40 gr bullets with a BC of 0.128 and an average muzzle velocity of 1050 fps. It is assumed that the actual velocity varies from 1040 to 1060 fps with the vertical tuned out. The first case (bottom curves) is where the vertical is tuned out at 50 yards. In this case the vertical at 100 yards is 7.79-7.46 or 0.33”. The rifle is not in tune for 100 yards.

In the second case the vertical is tuned out at 100 yards. But in this case the vertical at 50 yards is 3.89-3.73 or 0.16”.
Anyone can calculate this for their rifle & ammo using free ballistic software. For small variations is muzzle velocity a 22LR rifle in tune at 50 yards is NOT in tune at 100 yards.

LAUNCH ANGLE & DROP.... For the 1040 fps and 1060 fps bullets to strike at the same elevation at the 100 yard target, the launch angle for the 1040 fps bullet has to be elevated 0.2218 degrees above that of the 1060 fps bullet. If the muzzle were somehow fixed in space so that both bullets were launched at exactly the same angle, then the 1040 fps bullet would strike the 100 yard target 0.40" lower than the 1060 fps bullet. It is not rocket science that the slower bullet will drop more in traveling to the target.

Vibe,
I am amazed at your patience. Keep up the good work.:)

Keith
Click to expand...
 
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shooter65 said:
With a 50 yard zero it takes 25 moa of elevation to reach 200 yards with my rifle. A tuned barrel is a tuned barrel regardless of the distance you are shooting.

When I shoot with the same rifle / ammo combo with it takes a total of 48 moa of elevation with the Bushnell 6500 4.5-30x50 scope set on 4.5 power and using the last mildot. In light winds, hits at 400 yards were very consistent. Shooting anything from steel to stones.

5mildots from center at 4.5X would be ~11.2mil which equals ~ 38moa + 48moa = ~86moa ~30FT of drop
Click to expand...

I, in general, agree with the K.I.S.S. principle you espouse, so let's just take one sentence from Varmint Al:

For the 1040 fps and 1060 fps bullets to strike at the same elevation at the 100 yard target, the launch angle for the 1040 fps bullet has to be elevated 0.2218 degrees above that of the 1060 fps bullet.

Do you agree with this? If not, then by what other mechanism can these two bullets with different velocities strike the target at the same elevation?
 
I guess some of us agree that the muzzle does not stop in the parallel position. So either the faster or slower bullet would exit at the peak or valley of the muzzle to strike at the same point of impact.

Have you personally tried to shoot different speeds of ammo at different distances to see is they had the same point of impact?

If not, try it and report back your findings.
 
shooter65 said:
I guess some of us agree that the muzzle does not stop in the parallel position. So either the faster or slower bullet would exit at the peak or valley of the muzzle to strike at the same point of impact.

Have you personally tried to shoot different speeds of ammo at different distances to see is they had the same point of impact?

If not, try it and report back your findings.
Click to expand...

The peak or valley of muzzle angular motion is not where tuning is best. The slower bullet leaves the muzzle later and drops more on its way to the target. That's why the muzzle must be pointed higher for it to hit at the same elevation as the faster bullet. The difference in muzzle exit time between the fast and slow bullets is small - fractions of a millisecond. So, for the muzzle angle to increase enough in that short time, it needs to be moving fast. The peak and valley are where the muzzle angle is moving slow, so neither is conducive to tuning. Somewhere between the peak and valley, on the upslope, is where positive compensation happens.

I am mostly a centerfire shooter, so shooting different speeds is a simple matter of loading a range of powder charges. Yes, I have done this (ladder testing) and have reported results on this forum. It works. I found a different tune for 100 yards and 200 yards.

How about you?
 
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