impact and velocity

zeisloft · August 17, 2005, 04:13 PM

In working up a load, over the years I have noticed in several of my rifles, low velocity impacts at 7:30 mid velocities impact in the 10 ring and high velocity at 1:30. Same bullet, same everything, except quanity of powder. I can get good 1/2-3/4" groups at all o'colcks (100yds). Does twist have something to do with it? I assume it is just coincedence however it is a 14 right (.222 CZ527). The individual groups are linear along a 45 degree line about 1 1/2 inches apart. Many other of my guns produce similar "trends" but the "grouping" is not as pronounced.

Heres my procedure:
Shooting from a solid and constant rest.
Shooting a "cool" barrel (3 quick fliers, run a patch, wait 3-5 mins shoot 1, run a patch, wait, shoot. 1 shot every 3-5 mins)
I'm shooting 5 shot groups.
New target for every string.

Any Ideas? I sure dont mind the accuracy, just curious.
~z

tintcutter · August 17, 2005, 05:23 PM

Now this is a good question.

dfaugh · August 18, 2005, 08:10 AM

I went through something similar, as a result of my scope (crosshairs)not being dead level...In other, words a horizontal adjustment would make a slight vertical adjustment and vice-versa...changing ammo not only changed POI vertically (as you would expect), but also horizontally, too...Mine was not nearly as pronounced as what you describe, though. More like 6:30-7:00 o'clock and 12:30-1:00 clock. Not sure if this makes sense ornot, hopefully someone else will chime in.

zeisloft · August 18, 2005, 08:43 AM

dfaugh, I dont think it is the scope, with the string at 45 degrees, I would think misalignment would pretty obvious. Also, I am not making any scope adjustment. And yes, everything is tight, this was one of the first things I considered. I just do not understand the cause...Harmonics has been my best guess, it just seems odd to be grouping. I figure harmonics would produce more of a scatter gun effect untill the rught load is dialed in, at least, thats what Ive seen.
~z

zeisloft · August 19, 2005, 12:30 PM

anyone...
~z

**Mal H** · August 19, 2005, 01:15 PM

Upon reading your results, my first guess was also harmonics as you thought it might be. Barrels can have a whip effect in almost any direction, tons of variables come into play. If the stringing had been vertical, then it would, obviously, just be a matter of bullet speed and drop.

I think you might be able to prove it (if possible) by changing the barrel harmonic characteristics by placing a shim under the barrel near the front of the stock. If the stringing changes direction or magnitude, then harmonics is most likely the culprit.

I don't see how the scope could be at fault (assuming you keep a constant POA and not touching the scope adjustment between groups) unless it is moving uniformly from the mid point up to NE and back to SW with the change in loads. Can you say "impossible"? I knew you could.

zeisloft · August 19, 2005, 03:25 PM

Thanks Mal, This is obviously not a problem in the sense of most problems ie nothing went BOOB and I can still count to 21 without the aid of another person. I just found it curious and was looking for the cause. I will look into your shim idea to check if it is harmonic, it just seemed wierd that there would be three distinctly "sweet" resonance frequencies. And the fact that they are linear along a 45 makes it that much stranger.
~z

**Mal H** · August 19, 2005, 03:52 PM

"... nothing went BOOB ..."

Thank God! You don't want that to happen at the range. Throws your aim off something terrible!

zeisloft · August 19, 2005, 04:26 PM

Mal, I dont know to that was a slip up in my typing or maybe my mind is in another place. May I rephrase..."nothing went BOOM"...there, much better.
~z

tintcutter · August 19, 2005, 11:00 PM

The RPM of those three groups are what exactly? Did you Chronograph? I would imagine the angular momentum found in the rotation to be meaningful.

2800 fps = 2,352,000 rpm
3000 fps = 2,520,000 rpm
3200 fps = 2,688,000 rpm

these are not small differences.

does a bullet of lighter weight but similar speed to one of the groups place itself on the paper in a similar location only higher?

**Unclenick** · August 19, 2005, 11:17 PM

z,

I would vote with harmonics except for the fact you mentioned observing this in several rifles. Most rifles will string vertically as load changes, not on a diagonal. Harold R. Vaughn (Rifle Accuracy Facts, Precision Shooting pub, 2nd Ed. 2000) measures and reports the effects of barrel vibration in some detail in chapter 4. He also describes how axially asymmetric moments induce vibration in conjunction with recoil and cause stringing. It is this latter point that makes me wonder if this isn't something in the way you mount these weapons? I suggest you try shooting from your weak side with the rest of the setup the same. If the diagonal either goes away or moves to a 10:30/4:30 axis, you'll know it is related to how you hang on to the gun.

Another possibility is, if your rifles are all the same make and style of action and bedding, that it may be an inherent asymmetry in that configuration rather than your hold. Try switching sides and let us know what happens?

Nick

**Mal H** · August 19, 2005, 11:23 PM

tintcutter - I didn't do the math, but I have a feeling you are off by a factor of 10. Bullet rotational speed in the ball park of 200,000 RPM's is common, but I think a bullet rotating at over 2 million RPM's would fly apart. In fact, I think anything much larger than an electron would fly apart at that rotational speed.

Unclenick - good ideas. I hadn't noticed that he mentioned that the phenomenon happened with several rifles - that is very unusual.

smedley · August 20, 2005, 12:18 AM

Z,
In my opinion, and you know how those are, I am thinking that your scopes are canted to the bore of the rifle. It will not take much to do this.
I work up loads going up by 0.3 grns and it shows up if the scope is canted just a little. They look good to me but when I start to shoot it will show up going from a lower velocity to a higher velocity.
If you are getting this same, SAME, effect in other rifles, my guess is it may look good to your eye but is tipped a little. By shooting good groups, I don't think it is a harmonics or a bedding problem, espcially if it is happening going from lower to higher velocities in more than one rifle.

Smedley

Put it in at the bench and send it out down the barrel!!

**Mal H** · August 20, 2005, 08:23 AM

smedley, I would agree with you if the scope was being adjusted for the various loads, but if it isn't. Therefore the scope shouldn't enter into the equation. If the scope is always aimed at the same spot for the various loads (the same as sighting through the bore at the same spot), then the loads themselves along with the barrel whip will be the determining factors in POI.

All this is assuming several things - zeisloft is using a solid bench rest; no scope adjustments; no unusual grip on the rifle when firing, etc.

smedley · August 20, 2005, 08:36 AM

Mal H,
I guess I was stating my opion on what I do. I always aim for the same point on the target as do my increasing velocity loads. But as I read, and Z you will have to help us out with this, he shoots a group at one velocity then shoots another group increasing velocity and again and again. As he shoots these good groups they (groups) start flanking arcoss the target.
If this is the case and the same point of aim is used throughout, then I would bet on the scope being canted. The other reason I suggest canted is it happening on more than one rifle and if it his eye setting them off by a little bit on top of the rifle and then putting the cross hair flat on the target it will show a flacking string. When were taking MOA it only take a small amount of vertical crosshair cant to have this show up down at the target.

Smedley

Put it in at the bench send it out down the barrel

**Unclenick** · August 20, 2005, 08:49 AM

The only way I can think the scope might be involved is if he were shooting an M1-D and/or other rifles with offset scope mounts. The involvement would be the scope and mount mass being off vertical center (and not the scope setting, as Mal points out). This revives the question of off-center pressure points. In addition to shoulder placement, some guns are now arriving with side sling mounts (my Steyr Scout, for example). I just can't imagine all his rifles are going to have these unusual features, so I return to placement of the body mass behind the gun.

In position shooting I would also be looking for first or second trigger finger segment stock drag, the leftward pressure (for a northpaw hold) tending to have more effect on group placement when barrel time is greater. I, and numerous other service rifle match shooters need to add a couple clicks of windage at different positions, 300 yard timed fire in particular, just because of the position mechanics affecting left/right recoil moments. But off a bench, that doesn't seem likely to be so significant; nonetheless, something to be aware of.

I would be curious to know what z's 200 yard POI is after zeroing at 100?

Nick

**Mal H** · August 20, 2005, 08:53 AM

I trust zeisloft would notice a 45 degree cant on the scope.

If sighting through the bore at the exact same spot, does it matter how the remainder of the rifle is oriented? Does it even matter if there is a scope at all? I believe the rifle could be laying on it's side (on a solid rest) and the results for varying power loads should still be the same - vertical stringing. Take this to the extreme - there is no "rest of the rifle", i.e., we are using a proofing barrel and universal receiver bolted to the bench. The results should again be vertical stringing. Now replace the barrel only with zeisloft's barrel and compare the results. See what I mean?

**Unclenick** · August 20, 2005, 09:00 AM

Mal,

Not scope cant. As you said, scope alignment is irrelevant once zero is established. I am referring to the offset scope mounts that are left of the original iron sights' line of sight. Particularly if the mount is steel and has some mass, this moves the center of mass of the rifle left of center of the bore axis, causing a recoil moment that will tend to swing the muzzle to the right as well as up. More so with more bullet acceleration (hotter load).

Nick

Foxman · August 20, 2005, 09:21 AM

I have noticed a similar thing on occasion and originally thought about bullet rotaton speed, i.e. if the wind was horizontally from the right and the bullet rotation was right hand, it would have a tendency to climb and go to the left, but later thought that was not a complete answer. So I tend to go with the barrel whip camp on this.
I have also had a scope with almost invisible cant, but that gives say, up and to the right and down and to the left adjustment, but this is quickly obvious and easily fixed ( on some rifles anyway ). Interesting question.

**Mal H** · August 20, 2005, 09:30 AM

Unclenick - sorry for the confusion; I was addressing smedley, but failed to say so. You and I were posting at approx. the same time.

I think we all need a lot more info than is currently known about the circumstances and setup.

**Unclenick** · August 20, 2005, 09:44 AM

Mal,

Agreed. More data. z; get shootin' the experiments and let us know what guns are doing this and how they are configured?

Foxman,

Pick up a copy of Harold Vaughn's book, Rifle Accuracy Facts. Vaughn is a decorated fighter pilot who became an aerodynamics engineer and became the supervisor of the Sandia National Labs ballistics division. He knows more about ballistics than any other person writing for a general readership that I know of. He demonstrates an analysis using a six-degree-of-freedom computer ballistics program that shows all the effects of angle of repose induced yaw and rotational wobble and the effect of stability factor on the flight of a bullet. At 100 yards these effects will not significantly impact the size of the groups z is shooting. It would take a bench rest gun shooting in very low "ones" to show it at all. Vaughn puts the sideslip that results from gyrosopic effects at 0.215" slip to the right (for right-hand twist barrel) at 200 yards for a 90 grain 270 bullet. To see the difference in this drift caused by velocity variations in the load, you'd have to get a lot farther out there.

Nick

armedandsafe · August 20, 2005, 12:37 PM

If you want to see the effects of barrel whip on a slender barrel, hang a weight over the end of the barrel at the end (just behind the front sight) and see to where your groups move. I have done this with as small a weight as a box of .22LR on the end of a 26" 30-06. It is interesting. Use a forearm rest to take as much of the "people error" out of the test as possible.

Pops

Foxman · August 20, 2005, 12:47 PM

Thanks for that Unclenick, I certainly will get a copy, I find this interesting and could definitely use some more knowledge on it.
It's part of what makes shooting and reloading the fascinating subject it is, appreciate your help.
Mike

bugmantrap · August 20, 2005, 03:22 PM

I believe you provided the answer to your own question when you said low, med, and high vel loads. Speed in any load is never constant. Ask any chronograph. I have never had impact change directly up or down when I change the weight of the charge. Indeed, the bullet may impact any where on the target. Somr times the change is minute and others it is outragous. Try this some time, Run all three of your handloads through five shot groups and don't run a patch through the barrel. Give it time to cool between groups and take your time.Let us know the results. Bet it impacts differantly. My two cents
Trapper

tintcutter · August 20, 2005, 09:47 PM

Mal H

Sorry I had a 1 in 14 twist calculated as a 14 in 1. I thought it was the new math.

50 grain bullet at 3100 fps in the 1/14" should be 159,428 rpm

So what I meant to express was

2800fps = 144,000 rpm
3000fps = 154,286 rpm
3200fps = 164,572 rpm

So 10,000 rpm difference between. Still a big difference.

August 17, 2005, 04:13 PM	#1
zeisloft Senior Member Join Date: June 7, 2005 Location: Amarillo TX Posts: 419	impact and velocity In working up a load, over the years I have noticed in several of my rifles, low velocity impacts at 7:30 mid velocities impact in the 10 ring and high velocity at 1:30. Same bullet, same everything, except quanity of powder. I can get good 1/2-3/4" groups at all o'colcks (100yds). Does twist have something to do with it? I assume it is just coincedence however it is a 14 right (.222 CZ527). The individual groups are linear along a 45 degree line about 1 1/2 inches apart. Many other of my guns produce similar "trends" but the "grouping" is not as pronounced. Heres my procedure: Shooting from a solid and constant rest. Shooting a "cool" barrel (3 quick fliers, run a patch, wait 3-5 mins shoot 1, run a patch, wait, shoot. 1 shot every 3-5 mins) I'm shooting 5 shot groups. New target for every string. Any Ideas? I sure dont mind the accuracy, just curious. ~z __________________ A scalpel can be just as effective as a broadsword Obviously, Occam was not a reloader

August 17, 2005, 05:23 PM	#2
tintcutter Senior Member Join Date: January 4, 2005 Location: Alabama Posts: 207	Now this is a good question. __________________ The fine art of B.S. is not found in what is said, but in its plausibility.

August 18, 2005, 08:10 AM	#3
dfaugh Senior Member Join Date: January 17, 2002 Location: Upstate NY Posts: 1,715	Is this a scoped rifle? I went through something similar, as a result of my scope (crosshairs)not being dead level...In other, words a horizontal adjustment would make a slight vertical adjustment and vice-versa...changing ammo not only changed POI vertically (as you would expect), but also horizontally, too...Mine was not nearly as pronounced as what you describe, though. More like 6:30-7:00 o'clock and 12:30-1:00 clock. Not sure if this makes sense ornot, hopefully someone else will chime in. __________________ "If you Listen to Fools, the Mob Rules" "No one has the answer, but one thing is true. You'e got to turn on evil, when its coming after you. You've gotta face it down,and when it tries to hide, you've got to go in after it, and never be denied. Time is running out...Let's roll. Let's roll for freedom, let's roll for love. We're going after satan, on the wings of a dove. Let's roll for freedom, let's roll for truth. Let's not let our children grow up fearful in their youth."

August 18, 2005, 08:43 AM	#4
zeisloft Senior Member Join Date: June 7, 2005 Location: Amarillo TX Posts: 419	dfaugh, I dont think it is the scope, with the string at 45 degrees, I would think misalignment would pretty obvious. Also, I am not making any scope adjustment. And yes, everything is tight, this was one of the first things I considered. I just do not understand the cause...Harmonics has been my best guess, it just seems odd to be grouping. I figure harmonics would produce more of a scatter gun effect untill the rught load is dialed in, at least, thats what Ive seen. ~z __________________ A scalpel can be just as effective as a broadsword Obviously, Occam was not a reloader

August 19, 2005, 12:30 PM	#5
zeisloft Senior Member Join Date: June 7, 2005 Location: Amarillo TX Posts: 419	anyone... ~z __________________ A scalpel can be just as effective as a broadsword Obviously, Occam was not a reloader

August 19, 2005, 01:15 PM	#6
Mal H Staff Join Date: March 20, 1999 Location: Somewhere in the woods of Northern Virginia Posts: 16,955	Upon reading your results, my first guess was also harmonics as you thought it might be. Barrels can have a whip effect in almost any direction, tons of variables come into play. If the stringing had been vertical, then it would, obviously, just be a matter of bullet speed and drop. I think you might be able to prove it (if possible) by changing the barrel harmonic characteristics by placing a shim under the barrel near the front of the stock. If the stringing changes direction or magnitude, then harmonics is most likely the culprit. I don't see how the scope could be at fault (assuming you keep a constant POA and not touching the scope adjustment between groups) unless it is moving uniformly from the mid point up to NE and back to SW with the change in loads. Can you say "impossible"? I knew you could.

August 19, 2005, 03:25 PM	#7
zeisloft Senior Member Join Date: June 7, 2005 Location: Amarillo TX Posts: 419	Thanks Mal, This is obviously not a problem in the sense of most problems ie nothing went BOOB and I can still count to 21 without the aid of another person. I just found it curious and was looking for the cause. I will look into your shim idea to check if it is harmonic, it just seemed wierd that there would be three distinctly "sweet" resonance frequencies. And the fact that they are linear along a 45 makes it that much stranger. ~z __________________ A scalpel can be just as effective as a broadsword Obviously, Occam was not a reloader

August 19, 2005, 03:52 PM	#8
Mal H Staff Join Date: March 20, 1999 Location: Somewhere in the woods of Northern Virginia Posts: 16,955	"... nothing went BOOB ..." Thank God! You don't want *that* to happen at the range. Throws your aim off something terrible!

August 19, 2005, 04:26 PM	#9
zeisloft Senior Member Join Date: June 7, 2005 Location: Amarillo TX Posts: 419	Mal, I dont know to that was a slip up in my typing or maybe my mind is in another place. May I rephrase..."nothing went BOOM"...there, much better. ~z __________________ A scalpel can be just as effective as a broadsword Obviously, Occam was not a reloader

August 19, 2005, 11:00 PM	#10
tintcutter Senior Member Join Date: January 4, 2005 Location: Alabama Posts: 207	The RPM of those three groups are what exactly? Did you Chronograph? I would imagine the angular momentum found in the rotation to be meaningful. 2800 fps = 2,352,000 rpm 3000 fps = 2,520,000 rpm 3200 fps = 2,688,000 rpm these are not small differences. does a bullet of lighter weight but similar speed to one of the groups place itself on the paper in a similar location only higher? __________________ The fine art of B.S. is not found in what is said, but in its plausibility.

August 19, 2005, 11:17 PM	#11
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	z, I would vote with harmonics except for the fact you mentioned observing this in several rifles. Most rifles will string vertically as load changes, not on a diagonal. Harold R. Vaughn (Rifle Accuracy Facts, Precision Shooting pub, 2nd Ed. 2000) measures and reports the effects of barrel vibration in some detail in chapter 4. He also describes how axially asymmetric moments induce vibration in conjunction with recoil and cause stringing. It is this latter point that makes me wonder if this isn't something in the way you mount these weapons? I suggest you try shooting from your weak side with the rest of the setup the same. If the diagonal either goes away or moves to a 10:30/4:30 axis, you'll know it is related to how you hang on to the gun. Another possibility is, if your rifles are all the same make and style of action and bedding, that it may be an inherent asymmetry in that configuration rather than your hold. Try switching sides and let us know what happens? Nick Last edited by Unclenick; August 20, 2005 at 08:29 AM.

August 19, 2005, 11:23 PM	#12
Mal H Staff Join Date: March 20, 1999 Location: Somewhere in the woods of Northern Virginia Posts: 16,955	tintcutter - I didn't do the math, but I have a feeling you are off by a factor of 10. Bullet rotational speed in the ball park of 200,000 RPM's is common, but I think a bullet rotating at over 2 million RPM's would fly apart. In fact, I think anything much larger than an electron would fly apart at that rotational speed. Unclenick - good ideas. I hadn't noticed that he mentioned that the phenomenon happened with several rifles - that is very unusual.

August 20, 2005, 12:18 AM	#13
smedley Member Join Date: June 21, 2005 Location: NW washington with property in E. Washington Posts: 43	Z, In my opinion, and you know how those are, I am thinking that your scopes are canted to the bore of the rifle. It will not take much to do this. I work up loads going up by 0.3 grns and it shows up if the scope is canted just a little. They look good to me but when I start to shoot it will show up going from a lower velocity to a higher velocity. If you are getting this same, SAME, effect in other rifles, my guess is it may look good to your eye but is tipped a little. By shooting good groups, I don't think it is a harmonics or a bedding problem, espcially if it is happening going from lower to higher velocities in more than one rifle. Smedley Put it in at the bench and send it out down the barrel!!

August 20, 2005, 08:23 AM	#14
Mal H Staff Join Date: March 20, 1999 Location: Somewhere in the woods of Northern Virginia Posts: 16,955	smedley, I would agree with you if the scope was being adjusted for the various loads, but if it isn't. Therefore the scope shouldn't enter into the equation. If the scope is always aimed at the same spot for the various loads (the same as sighting through the bore at the same spot), then the loads themselves along with the barrel whip will be the determining factors in POI. All this is assuming several things - zeisloft is using a solid bench rest; no scope adjustments; no unusual grip on the rifle when firing, etc.

August 20, 2005, 08:36 AM	#15
smedley Member Join Date: June 21, 2005 Location: NW washington with property in E. Washington Posts: 43	Mal H, I guess I was stating my opion on what I do. I always aim for the same point on the target as do my increasing velocity loads. But as I read, and Z you will have to help us out with this, he shoots a group at one velocity then shoots another group increasing velocity and again and again. As he shoots these good groups they (groups) start flanking arcoss the target. If this is the case and the same point of aim is used throughout, then I would bet on the scope being canted. The other reason I suggest canted is it happening on more than one rifle and if it his eye setting them off by a little bit on top of the rifle and then putting the cross hair flat on the target it will show a flacking string. When were taking MOA it only take a small amount of vertical crosshair cant to have this show up down at the target. Smedley Put it in at the bench send it out down the barrel

August 20, 2005, 08:49 AM	#16
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	The only way I can think the scope might be involved is if he were shooting an M1-D and/or other rifles with offset scope mounts. The involvement would be the scope and mount mass being off vertical center (and not the scope setting, as Mal points out). This revives the question of off-center pressure points. In addition to shoulder placement, some guns are now arriving with side sling mounts (my Steyr Scout, for example). I just can't imagine all his rifles are going to have these unusual features, so I return to placement of the body mass behind the gun. In position shooting I would also be looking for first or second trigger finger segment stock drag, the leftward pressure (for a northpaw hold) tending to have more effect on group placement when barrel time is greater. I, and numerous other service rifle match shooters need to add a couple clicks of windage at different positions, 300 yard timed fire in particular, just because of the position mechanics affecting left/right recoil moments. But off a bench, that doesn't seem likely to be so significant; nonetheless, something to be aware of. I would be curious to know what z's 200 yard POI is after zeroing at 100? Nick

August 20, 2005, 08:53 AM	#17
Mal H Staff Join Date: March 20, 1999 Location: Somewhere in the woods of Northern Virginia Posts: 16,955	I trust zeisloft would notice a 45 degree cant on the scope. If sighting through the bore at the exact same spot, does it matter how the remainder of the rifle is oriented? Does it even matter if there is a scope at all? I believe the rifle could be laying on it's side (on a solid rest) and the results for varying power loads should still be the same - vertical stringing. Take this to the extreme - there is no "rest of the rifle", i.e., we are using a proofing barrel and universal receiver bolted to the bench. The results should again be vertical stringing. Now replace the barrel only with zeisloft's barrel and compare the results. See what I mean?

August 20, 2005, 09:00 AM	#18
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Mal, Not scope cant. As you said, scope alignment is irrelevant once zero is established. I am referring to the offset scope mounts that are left of the original iron sights' line of sight. Particularly if the mount is steel and has some mass, this moves the center of mass of the rifle left of center of the bore axis, causing a recoil moment that will tend to swing the muzzle to the right as well as up. More so with more bullet acceleration (hotter load). Nick

August 20, 2005, 09:21 AM	#19
Foxman Senior Member Join Date: August 13, 2005 Posts: 466	I have noticed a similar thing on occasion and originally thought about bullet rotaton speed, i.e. if the wind was horizontally from the right and the bullet rotation was right hand, it would have a tendency to climb and go to the left, but later thought that was not a complete answer. So I tend to go with the barrel whip camp on this. I have also had a scope with almost invisible cant, but that gives say, up and to the right and down and to the left adjustment, but this is quickly obvious and easily fixed ( on some rifles anyway ). Interesting question.

August 20, 2005, 09:30 AM	#20
Mal H Staff Join Date: March 20, 1999 Location: Somewhere in the woods of Northern Virginia Posts: 16,955	Unclenick - sorry for the confusion; I was addressing smedley, but failed to say so. You and I were posting at approx. the same time. I think we all need a lot more info than is currently known about the circumstances and setup.

August 20, 2005, 09:44 AM	#21
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Mal, Agreed. More data. z; get shootin' the experiments and let us know what guns are doing this and how they are configured? Foxman, Pick up a copy of Harold Vaughn's book, Rifle Accuracy Facts. Vaughn is a decorated fighter pilot who became an aerodynamics engineer and became the supervisor of the Sandia National Labs ballistics division. He knows more about ballistics than any other person writing for a general readership that I know of. He demonstrates an analysis using a six-degree-of-freedom computer ballistics program that shows all the effects of angle of repose induced yaw and rotational wobble and the effect of stability factor on the flight of a bullet. At 100 yards these effects will not significantly impact the size of the groups z is shooting. It would take a bench rest gun shooting in very low "ones" to show it at all. Vaughn puts the sideslip that results from gyrosopic effects at 0.215" slip to the right (for right-hand twist barrel) at 200 yards for a 90 grain 270 bullet. To see the difference in this drift caused by velocity variations in the load, you'd have to get a lot farther out there. Nick

August 20, 2005, 12:37 PM	#22
armedandsafe Senior Member Join Date: January 9, 2005 Location: Moses Lake WA Posts: 1,001	If you want to see the effects of barrel whip on a slender barrel, hang a weight over the end of the barrel at the end (just behind the front sight) and see to where your groups move. I have done this with as small a weight as a box of .22LR on the end of a 26" 30-06. It is interesting. Use a forearm rest to take as much of the "people error" out of the test as possible. Pops __________________ Armed and Safe: Not just a theory If it time to bury them, it is time to dig them up. Remember, "Behind every blade of grass."

August 20, 2005, 12:47 PM	#23
Foxman Senior Member Join Date: August 13, 2005 Posts: 466	Thanks for that Unclenick, I certainly will get a copy, I find this interesting and could definitely use some more knowledge on it. It's part of what makes shooting and reloading the fascinating subject it is, appreciate your help. Mike

August 20, 2005, 03:22 PM	#24
bugmantrap Member Join Date: August 19, 2005 Location: massachusettes Posts: 57	I believe you provided the answer to your own question when you said low, med, and high vel loads. Speed in any load is never constant. Ask any chronograph. I have never had impact change directly up or down when I change the weight of the charge. Indeed, the bullet may impact any where on the target. Somr times the change is minute and others it is outragous. Try this some time, Run all three of your handloads through five shot groups and don't run a patch through the barrel. Give it time to cool between groups and take your time.Let us know the results. Bet it impacts differantly. My two cents Trapper

August 20, 2005, 09:47 PM	#25
tintcutter Senior Member Join Date: January 4, 2005 Location: Alabama Posts: 207	Mal H Sorry I had a 1 in 14 twist calculated as a 14 in 1. I thought it was the new math. 50 grain bullet at 3100 fps in the 1/14" should be 159,428 rpm So what I meant to express was 2800fps = 144,000 rpm 3000fps = 154,286 rpm 3200fps = 164,572 rpm So 10,000 rpm difference between. Still a big difference. __________________ The fine art of B.S. is not found in what is said, but in its plausibility.