Spin drift seems excessive

[STOMP442]

No flags but plenty of brush and weeds on the berms for a good estimation. I also have a wind meter. What little puffs of wind there is, is not nearly enough for the amounts of drift i am seeing.

 

[BoydAllen]

Given that we are all guessing because we do not have your rifle in front of us, here is what I use to mount scopes. With the rifle in a vise that I can adjust for tilt, I first use the tool to put the center of the scope directly over the center of the barrel (something simply leveling the action and then the reticle does not guarantee at all) and then level the scope within the rings. http://www.brownells.com/gunsmith-t...ers/vertical-reticle-instrument-prod6097.aspx
I invested in this tool many years ago, and have used it to set up scopes for myself, as well as friends who have shot theirs at long ranges. It seems to work very well. Another thing that I do is to use a padded wooden V block setup to adjust my cross hair intersection so that it is centered to the scope tube, by rotating the scope in the Vs and adjusting the turrets to the point where the intersection does not move as the scope is rotated. This is more precise than counting clicks. Once I have the reticle centered, I can adjust my rings so that the windage is close to correct (adjustable rings or offset inserts) and then use the elevation turret and a slight windage adjustment to sight in the rifle. IMO having the scope near the center of its windage adjustment is a good idea. Good luck with your problem. Of course for rings without plastic inserts I always lap them. Let us know if you solve it, and how.

 

[DCRYDER]

Instead of "timing" most people call it "indexing".

No barrel is perfectly straight, even custom barrels can be off as much as .025" at the muzzle when breech is indicated in with range rod from what I've seen.

I always time or index to where it shoots straight up 12 o'clock. Then problems like this are eliminated and helps with elevation for long range.

Hey at 12 o'clock maybe it should be called "timed".

 

[savagedasher]

Instead of "timing" most people call it "indexing".

No barrel is perfectly straight, even custom barrels can be off as much as .025" at the muzzle when breech is indicated in with range rod from what I've seen.

I always time or index to where it shoots straight up 12 o'clock. Then problems like this are eliminated and helps with elevation for long range.

Hey at 12 o'clock maybe it should be called "timed".

When the head space is set the barrel is then timed for the direction that the bullet is going to go. The one that I was talking about to me is time to where the bullet is going to the right . Every time the yartage is increased it goes farther right . It can be verified easy put a vertical line for aim point and shoot it at 50 100 200 and 300 All 4 shot will be on the same vertical line . If not the barrel is not timed to 12 or 6 orention . Larry

 

[Sheldon N]

"Barrel timing" (whatever that is??) cannot cause this problem - IF you launch a bullet and it hits the POA at 100 yds, then it started it's life in a straight line - nothing in the barrel can cause it to start traveling in a different direction.

This is correct. Barrel timing is a non-issue. Once the bullet leaves the bore it is traveling in a straight line. Once the scope is zeroed at 100 yards the bullet path and the scope line of sight are aligned. The only potential issue at that point is mechanical offset for the bore being horizontally offset from the scope. Barrel curvature is extremely minor and not enough to cause this kind of deviation. It's something that's on the order of fractions of an inch at distance, essentially non-measurable.

Spin drift should be roughly 1.5 to 2" at 500 yards with your setup. I'd go back to looking at rifle cant or scope tracking as the remaining cause. Just one degree of offset could cause the remaining 4" of drift.

 

[DHuffman]

When the head space is set the barrel is then timed for the direction that the bullet is going to go. The one that I was talking about to me is time to where the bullet is going to the right . Every time the yartage is increased it goes farther right . It can be verified easy put a vertical line for aim point and shoot it at 50 100 200 and 300 All 4 shot will be on the same vertical line . If not the barrel is not timed to 12 or 6 orention . Larry

I understand what you're saying but don't understand how you set the headspace then time the barrel without changing the headspace setting. If I understand correctly the most it could be off is 90 degrees, probably less but you would have to set it pointing up or down whichever required the smaller correction to have the least effect on headspace. How does this 0 - 90 degree timing correction not affect headspace?

 

[savagedasher]

I understand what you're saying but don't understand how you set the headspace then time the barrel without changing the headspace setting. If I understand correctly the most it could be off is 90 degrees, probably less but you would have to set it pointing up or down whichever required the smaller correction to have the least effect on headspace. How does this 0 - 90 degree timing correction not affect headspace?

The timing or the clocking if the barrel is determined by head space . If the chambering is done without determine Orention The barrel can be aimed in any direction . If it is pointing right the bullet continue going right and down . Larry

 

[Sheldon N]

The timing or the clocking if the barrel is determined by head space . If the chambering is done without determine Orention The barrel can be aimed in any direction . If it is pointing right the bullet continue going right and down . Larry

Not correct Larry, see my message above. Once the rifle is zeroed at 100 yards the only remaining issue is mechanical offset of the bore from underneath the scope due to bore curvature. You might lose some windage/elevation adjustment range in your scope due to having to correct for the offset impact, but once zeroed it becomes a non-issue.

The bore and action would literally have to be sitting ONE INCH to the left underneath the scope in order to create the amount of offset we are talking about here.

 

[savagedasher]

Not correct Larry, see my message above. Once the rifle is zeroed at 100 yards the only remaining issue is mechanical offset of the bore from underneath the scope due to bore curvature. You might lose some windage/elevation adjustment range in your scope due to having to correct for the offset impact, but once zeroed it becomes a non-issue.

The bore and action would literally have to be sitting ONE INCH to the left underneath the scope in order to create the amount of offset we are talking about here.

Not correct Larry, see my message above. Once the rifle is zeroed at 100 yards the only remaining issue is mechanical offset of the bore from underneath the scope due to bore curvature. You might lose some windage/elevation adjustment range in your scope due to having to correct for the offset impact, but once zeroed it becomes a non-issue.

The bore and action would literally have to be sitting ONE INCH to the left underneath the scope in order to create the amount of offset we are talking about here.

If the curve in the barrel makes your bullet impact to the right at 100 And you adjust the scope To the point of that . Would the bullet not continue going right. When you increase the distance you must move your scope to chase the direction the bullet is going . Larry

 

[Sheldon N]

If the curve in the barrel makes your bullet impact to the right at 100 And you adjust the scope To the point of that . Would the bullet not continue going right. When you increase the distance you must move your scope to chase the direction the bullet is going . Larry

Yes, that's correct. The issue though is the question of how large that error is going to be. Let's play it out with an exaggerated hypothetical scenario...

Start with a terrible chamber and barrel timing job. Indexed at 3:00. You go to the range and it hits a full 2 feet to the right.
You correct that issue by dialing in windage on your scope. It's so bad that you have to use up almost all your windage adjustment capability to set your 100 yard zero.

Now here's where you have to visualize what's happening. When you are setting your zero by dialing windage, the thing you are fixing is that the path of the bullet doesn't line up with the path of the scope/reticle. You are fixing the offset problem that is already present in your gun.

The action might be sitting underneath the scope directly, but what really matters is what's happening in the last few inches of the barrel. If those are pointing to the right, then the bullet goes to the right on a straight line. That straight line, extended back to your action, may be offset to the left...even if the action itself isn't.

The question then becomes... how big is that "theoretical" offset of the bullet path vs the optical path of the scope? We're looking at 2 straight lines that intersect at 100 yards, and the bullet path has to go through the muzzle (at whatever angle it's pointed). The muzzle is about 1 yard in front of the action, so let's call it a 100:1 ratio. That means if your bullet is hitting 2 foot to the right, the offset between the bullet path and the scope at the point of the action is 1/100th of that amount or .24".

Now since you set your zero at 100 yards, the impact is going to be true at 100 yards. If you go another 100 yards beyond that, the path of the bullet and the path of the scope optics are going to diverge the same amount as they are offset at 100 yards... or 1/4". And every hundred yards beyond that point will add another 1/4". So in our worst case scenario you'd end up with 1" of lateral offset at 500 yards.

So in order for the OP's problem to be related to barrel chambering, it would need to be FOUR TIMES worse than the scenario above. In other words, it would need to be so bad that the impact was 8 feet to the right when he went to zero at 100 yards, and that's so bad that he wouldn't have been able to dial enough windage to set his zero to begin with.

 

[savagedasher]

Yes, that's correct. The issue though is the question of how large that error is going to be. Let's play it out with an exaggerated hypothetical scenario...

Start with a terrible chamber and barrel timing job. Indexed at 3:00. You go to the range and it hits a full 2 feet to the right.
You correct that issue by dialing in windage on your scope. It's so bad that you have to use up almost all your windage adjustment capability to set your 100 yard zero.

Now here's where you have to visualize what's happening. When you are setting your zero by dialing windage, the thing you are fixing is that the path of the bullet doesn't line up with the path of the scope/reticle. You are fixing the offset problem that is already present in your gun.

The action might be sitting underneath the scope directly, but what really matters is what's happening in the last few inches of the barrel. If those are pointing to the right, then the bullet goes to the right on a straight line. That straight line, extended back to your action, may be offset to the left...even if the action itself isn't.

The question then becomes... how big is that "theoretical" offset of the bullet path vs the optical path of the scope? We're looking at 2 straight lines that intersect at 100 yards, and the bullet path has to go through the muzzle (at whatever angle it's pointed). The muzzle is about 1 yard in front of the action, so let's call it a 100:1 ratio. That means if your bullet is hitting 2 foot to the right, the offset between the bullet path and the scope at the point of the action is 1/100th of that amount or .24".

Now since you set your zero at 100 yards, the impact is going to be true at 100 yards. If you go another 100 yards beyond that, the path of the bullet and the path of the scope optics are going to diverge the same amount as they are offset at 100 yards... or 1/4". And every hundred yards beyond that point will add another 1/4". So in our worst case scenario you'd end up with 1" of lateral offset at 500 yards.

So in order for the OP's problem to be related to barrel chambering, it would need to be FOUR TIMES worse than the scenario above. In other words, it would need to be so bad that the impact was 8 feet to the right when he went to zero at 100 yards, and that's so bad that he wouldn't have been able to dial enough windage to set his zero to begin with.

You figure it out I know it isn't spin drift or scope cant Larry

 

[Eddie Harren]

You figure it out I know it isn't spin drift or scope cant Larry

That is the most scientific statement ever heard, in this sandbox, on this playground. Are you taking your marbles and going home?

 

[dmoran]

You figure it out I know it isn't spin drift or scope cant Larry

 

[Sheldon N]

You figure it out I know it isn't spin drift or scope cant Larry

Just trying to help you out Larry. Even old dogs can learn new tricks.

 

[savagedasher]

Just trying to help you out Larry. Even old dogs can learn new tricks.

But seldom

 

[mac86951]

Random question what compass direction are you shooting?

 

[Eric Leonard]

does the rifle zero to the same point with multiple shooters,,it is not impossible for the shooter to induce that much zero shift and do it while shooting real good groups and do it consistent enough to be repeatable,,

 

[dmoran]

While I do agree with Larry that there can be advantages to timing a barrel for alignment to the sights by having the bores "high/low" timed to 12 or 6-o'clock. Or by having the "high" to 12-o'clock position/index for gains to over all turret travel. How ever, there is no guarantee that index point will be the most optimal accuracy wise.
Plus there are several aspects that can come into play that will grossly effect optimal barrel timings; If the receiver face and/or recoil-lug are not 100% square and flat, timing is out the window. Any induced stress at all when dialing the barrel in the lathe can and will induce a false high/low. Etc...

I've never seen proof that a straight, or relatively straight barrel bore is more accurate then a curved bore. In fact, the most accurate barrel I've ever had myself to date had a pronounced curve of several thousandths, and have heard from others over the years report the same thing, so which is actually better?

I have "spin tested" barrels for optimal positions, with what I call my "spin chassis" (pictured below), from which I can say there is more to optimal accuracy index/timing then just "clocking the high" to 12 or 6-o'clock.
Donovan

 

[potatoe]

While I do agree with Larry that there can be advantages to timing a barrel's for alignment to the sights by having the bores "high timed to 12 or 6-o'clock. Or by having the "high" to 12-o'clock position/index for gains to over all turret travel. How ever, there is no guarantee that index point will be the most optimal accuracy wise.
Plus there are several aspects that can come into play that will grossly effect optimal barrel timings; If the action face and/or recoil-lug are not 100% square, timing is out the window. Any stress at all when dialing the barrel in the lathe can and will induce a false high/low. Etc...

I've never seen proof that a straight, or relatively straight barrel bore is more accurate then a curved bore. In fact, the most accurate barrel I've ever had myself to date had a pronounced curve of several thousandths, and have heard from others over the years report the same thing, so which is actually better?

I have "spin tested" barrels for optimal accuracy position, with what I call my "spin chassis" (pictured below), from which I can honestly say there is more to an optimal accuracy index/timing then just putting a "high" to 12 or 6-o'clock.
Donovan

If I saw this at the range I would not be shooting and pull out a note pad

 

[DanSavage]

One thing you could look at is bullet holes shot on good quality white target paper at 100 yards. Look to see if the hole is perfectly round,, or is it slightly egg shaped horizontally.

It is possible that the bullet is traveling with the nose slightly to the right, the bullet may be stabilized and a sleep.

This is what I think the guys talking about the slightly curved barrel theory mean.

If this is the case, you will have to have a smith mark the barrel and clock it straight up then run a reamer in and set the barrel back a smidge. I have lots of Savage barrels for 2 actions and never have seen this issue.

Myself I would mark the end of the right side of the barrel near the muzzle and play with head space to see if it can be clocked up or down. It shouldn't effect head space a whole lot but it will. I set my head space up snug to new Lapua brass, and there seems to be some lee way with head space tolerances.