long range shooting problem

[joe3]

i have a couple of friends with an odd problem that i dont know the answer to. their long range setups is the exact same setup which is: a factory remington 300 ultra mag with the fluted varmint contour barrels. they are both shooting 210gr bergers with 92gr of h1000(velocity ~3050fps) fed 215m primers. nightforce scopes...... these guns shoot ~2" groups @200yards.

their problem is, when we are out shooting at 800-1200 yards, their guns always shoot to the right! i myself shoot a 7wsm with 162amax @3050fps. the other day we were all 3 shooting at 800 and 900 yard steel targets and i was dialing for little or no wind and they were dialing 2 or 3 moa. same thing happened to one of them when we shot at 1200yards on a different day, he had to dial 6 moa when i was at 2moa windage.....pretty calm day. same thing happens to him at his range at 1050yards. now when this all happened when we we're all shooting prone and off of bipods and sandbags.

i dont really know how they worked up their loads, so thats questionable. if it was their loads though, it would be more of a vertical problem rather than a windage problem....right? i do know that they do not put these bullets into the lands. they load them short enough to fit into their box magazine...that may be a problem. they use swivel bipods....ive thought that maybe they are getting torqued while shooting(i use a fixed bipod). i may have to shoot one of their guns on my bench off of my rest.



they are convinced that their twist rate is not fast enough for the bullet. they are ready to sell all of the 210bergers they have b/c of this.

any ideas?

 

[britz]

Two possible problems that I can think of would be spindrift and scope not being level. To be honest spindrift should only be around 10" at most at 1000, I think... so that really isn't that likely to be the problem... and I'm not even sure which way it should be depending on you twist ( I suspect that it would be a right twist and therefore be drifting to the right.)

However, the more likely culprit is that the scope is not mounted perfectly level on your rifle. If the scope is canted to the right slightly, when you turn your turret, the crosshairs will be moving slightly to the left as you dial for more range. This would cause you to aim farther right. It could also be that they are consistently canting the rifle while fireing... but I would suspect that they would be getting horizontal stringing if that was the case.
Good luck, Mark.

 

[joe3]

this is true, canting the rifle would cause this. i always shoot with a bubble level.....they dont.
how unlevel would the crosshairs have to be to create such a bullet drift at 800yards? should be noticeable....right?

 

[britz]

It takes more math that I'm willing to figure out on a saturday night lol! yes it would be noticeable. Just look at something half a mile away through your rifle scope and watch how far the bottom post of the duplex moves on the target when you cant your scope a little. 800 -1200 yards is a long ways off and the smallest movement makes a big difference. doesn't take much to move 20-30 inches

after I wrote that I had to take a shot at it... I'm thinking that from 100 yard sight in to 1200 yard sight in you have about 400 inches of elevation adjustment. to get roughly close I'm thinking you have a circle that is 800 inches in diameter x pie divided by 360 degrees will yield roughly 7 inches off per degree of cant off. so it will add up in a hurry!

 

[eshell]

I would agree that the reticle is likely canted.

This introduces two problems. First, the scope is leaning and the bullet doesn't not strike directly on the vertical wire. Then as we dial on elevation, we are also inadvertently adding windage.

 

[joe3]

he does level his scope with a double bubble level kit. (one on the action and one on the top of the scope turret). i may have to show him how to level his scope the Right way. i dont think highly of the double level kit that he thinks the world of. lol. after i do that i will have him shoot with a level on his rifle.
and me getting him to do all of this might take an arm and a leg! he's kinda thick headed. lol

 

[J E Custom]

I would agree that the reticle is likely canted.

This introduces two problems. First, the scope is leaning and the bullet doesn't not strike directly on the vertical wire. Then as we dial on elevation, we are also inadvertently adding windage.

+1
When you increase elevation ,you increase windage error if the scope is not level with the bullet
path.

simply holding the scope level will not fix the problem.

Place a piece of tape around the scope next to the scope ring and make a fine mark on the
tape at the seam of the scope ring and then loosen the scope rings just enough to rotate
the scope in the direction that you want to move the point of impact.(It won't take much)

Re-tighten and shoot, it should have about the same vertical point of impact (No windage
adjustments from 100 to 600yards).

J E CUSTOM

 

[woods]

The level-level-level

MidwayUSA - Wheeler Engineering Level-Level-Level Scope Crosshair Leveling Tool

never worked very well for me

Try the EXD device

BROWNELLS: EXD ENGINEERING VERTICAL RETICLE INSTRUMENT: EXD ENGINEERING

it will align the bore of your rifle and your scope and then you level your reticle

Here's some info on cant errors

Cant Errors - Long range shooting

 

[Mikecr]

The EXD device has potential..
Thing is, if you dial your elevation, it doesnt matter if the scope is level, nor gun, nor the reticle. Shooting plumb in the field here requires elevation TRAVEL thats plumb -while your at any reference level.
Unless your bore isn't centered, or the scope bases are off..
In this case you just have to shoot plumb lines at 2 distances and tweak the scope mounting till it works.

The EXD seems like it could be a good starting place if you can see the crosspoint or dot stay centered in it with elevation adjustment.
Can you?

 

[Ridge Runner]

On a large taget shoot a 200 yard group, then take a 4' level and plumb a straight line up from the group, crank 20 moa of up into the scope and see where the next group hits, if its off the plumb line you may hafta rotate the scope in the rings.
RR

 

[woods]

The EXD device has potential..
Thing is, if you dial your elevation, it doesnt matter if the scope is level, nor gun, nor the reticle. Shooting plumb in the field here requires elevation TRAVEL thats plumb -while your at any reference level.
Unless your bore isn't centered, or the scope bases are off..
In this case you just have to shoot plumb lines at 2 distances and tweak the scope mounting till it works.

The EXD seems like it could be a good starting place if you can see the crosspoint or dot stay centered in it with elevation adjustment.
Can you?

You can't see any part of the EXD through your scope. You see through the middle slot

and have to sight on a distant level object in order to level the reticle. The EXD is only to align your scope and bore and take all the cant out of the rifle while you level the reticle on that distant object. Here are instructions on using it

Vertical Retical Instrument

It is best to put an anti-cant device on while installing the scope and that way you can duplicate the uncanted rifle and scope in the field or on the bench. I prefer the ScopLevel

Scoplevel Anti Cant Leveling Device

 

[joe3]

i have never ran into this kind of problem. i always level my scopes by putting a level on my action or scope base and putting a 4' level out at 300yards and just line up the cross hairs vertically. i would like to try the technique of using a weighted rope and lining up the cross hair to it.

i will try to get him to do this today, i will let you guys know how it turns out. thanks for the help!

 

[MontanaRifleman]

Check this thread out. There's a good article on checking scope alignment...

http://www.longrangehunting.com/forums/f18/correctly-mounting-scope-rifle-43484/

 

[JeffVN]

Sounds like the scope reticle is canted. Spin drift will not get you nearly the error rate these guys are showing. Sadly, more than a few scopes leave teh factory with a slightly canted reticle.

Did they verify that the scope is verticle to the line of sight? I check mine by leveling the rifle using a USO action-based anti-cant indicator, but any such device will work. Step two is to look through the now leved rifle and verfiy that the verticle line on the reticle is following a true verticle line - in my case a piece of thin string with a 1lb weight tied to it and hangng freely. Chances are that their scopes are not oriented properly, and the canted reticle is causing the problem.

JeffVN