A mystery to me, hope some of you can help.

[308]

Have recently had the chance to air some of my stuff at 1000 yds.
Was impressed with my lowly 308 at a full grand. Shot less than moa groups, so I'm pleased. I know the 308 won't carry the ump for game at this distance but I'm learning with what I have so when I get a bigger gun I'll have some experience behind me, call it a long range learner gun if you will.
What I don't understand is the windage adjustments I'm having to make to hit center, at distance, starting with 3/4 moa at 400, with a pretty consistant, or even amount of increasing to 3.25 minutes at 1000 of left windage, this in basicly no wind conditions with wind flags outand may be noticeable at 200 and 300 also but we started at 400 the last two times we shot. I've leveled my scope with the weight hanging on the string trick and leveled the action with a level while mounting the scope and have it as level as I can get it. I don't mind having to make elevation and windage adjustments to hit but just don't understand the reason I'm having to. I have read the post about "law of repose" and this could be part of it but not all.I could be canting my rifle some but it's hard to beleive that I'm canting it consistantly the same from shot to shot and always in the same direction, cause once I make a windage adjustment it stays the same for that distance as long as the wind behaves.
I hope some of you can give me some answers or insight to what I'm seeing. Thank you Joey S AKA 308. sorry for being long winded

 

[sierra22]

Your rifle barrel wouldn't happen to have a right hand twist does it?

 

[Dave King]

Everyone loves a mystery!

Basics: Are you absolutely certain that your zero is centered vertically?

Canting can cause a problem.

"Spin Drift" or Yaw of Repose is an issue but I don't see this type "increasing windage" problem in the 308 Win rifles I shoot at 1000 yards.

What scope are you using? Could it be a problem with the erection system in the scope?

Do your other (I don't believe you have other's but) rifles exibit this same characteristic?

Have you shot with other folks on their rifles and experienced this same problem?

/r

 

[*WyoWhisper*]

Here's a thought.. recoil starts just after ignition right??

I have noticed if I do not use a firm grip the rifles will cant during recoil..usually to the right ( right hand twist? ) If in fact you use a "soft" grip this rifle could be canting during recoil and in acuality be canted when the bullet leaves the barrel..????

Food for thought....

 

[308]

The rifle wears a Leupold 6.5x20 w/the 30mm tube. It has a McMillan a2 or a3 stock. I'm shooting it off of a sinclair front rest and leather bag. It has a schneider no 8 contour barrel with 12 inch right hand twist. I'm shooting the 175 sierra match kings over 44 varget for a velocity of 2740 at ten feet over a pact chrono.
I'm not shooting it with a firm grip, holding the pistol grip lightly and squeezing the bag with my left hand, with minimal shoulder pressure and riding the recoil strait back.
I have some limited range time witha sendero in 7mm Rem Mag and it has shown a similar need for left windage but not as much as my 308 and I have not shot the 7 past 700.
I have it zeroed as near as I can get it at 100 and set my turret to zero.
I have the baer 2 piece bases with 20 mins of included angle and the burris signature 30 mm rings with the .010 insert under the back ring. My 100 yard zero is about 9 mins up from bottom in my scope so I have in the neighborhood of 60 mins I can go up.
No I have not had the opportunity to shoot someone elses rig at long range to see if it was a "me thang" instead of a gun thang.
I am going to put a scope level on it and see what changes that might make.
But even if I have to make two adjustments instead of one to get long range hits, What a blast that is. There would be no one hooked on drugs that ever got the chance to play this long range game. There is just something about the time lag from fireing to seeing and hearing the bullet make contact with steel way out yonder. thank you for your answers. 308

 

[*WyoWhisper*]

I too shoot the A3 stock in my 308.. because the grip is nearly verticle.. try this..

grip the palm area fairly firm.. apply presure with your 2nd and third finger straight back into your shoulder. Don't use your pinky or you'll torque the rifle during recoil. I have a pretty good grip on mine and pull it pretty good into my shoulder... havn't had the left windage problem out to 700...

 

[Guest]

[ 07-12-2003: Message edited by: S1 ]

 

[308]

S1 Thank you for your answer. That is a aspect I had not heard of or thought about. I did use a weighted string to align my scope but I aligned the string and the verticle cross hair with no thought to how the reticle would track.
As you stated you would need a very secure(anchored to the earth type clamp) way to clamp your rifle action while mounting the scope so your tracking is correctly up and down.
Could you describe the set up you use to insure your rifles are set up this way.
Barring that I will just have to test at each distance and record my windage corrections.
If my scope is not tracking parallel to the reticle- is this something Leupold would fix or could maybe The Premier Reticle guys make it right. Thank you for your valuable insights. 308

 

[308]

Thanks Blaine, I too believe this is most likely what I'm seeing with my setup too.
How did you fix your rifle rigid enough to eliminate any movement while running your adjustments up and down. Thanks for your time.

 

[Guest]

[ 07-12-2003: Message edited by: S1 ]

 

[Blaine Fields]

S1's post above shows the hot setup. Mine is a little more pedestrian.

I just use a cleaning cradle type thing that I've had for about twenty years. It has a large wooden vice at the end and lets me clamp the butt of the rifle so that practically speaking the rifle is immobile. When I twist the elevation knob, no significant movement is noted.

To get more distance, take the plumb bob out to the range. Get one of those metal clamps, not the "C" clamps, but the ones that have a long metal bar with a moveable lower clamp piece. You can clamp the thing to the target from with the bar sticking out from the target, either to the side or out in front. Take a string and plumb bob and hang it from the bar. That will give you the vertical line you need.

 

[Ian M]

S1,
When you say that you place the rifle in a barrel vise dead level (I would assume that is a 4" or 5" vise with padded jaws, please correct if wrong).
Could you explain how you level the rifle initially - using a level on the bridge or flat of a rail base? What kind of level (size) you prefer.
I very simply cannot level by eyeball - it ain't there - so would appreciate any suggestions.
Have you ever seen the procedure where you place two pieces of square bar stock (1/4" square rod about 12"-18" long) - on the top of the base under the scope and the other on the top of the turret cap and eyeball them level. Guess you could also do that with two rulers, I have never tried it either way.
I have the problem that my vise points the barrel at a nearby wall, don't have the option of dropping a line out a ways to plumb the crosshair.

Interested to hear what you think of the accessories for leveling crosshairs that are on the market - one by Stoney Point and the Reticle Leveler with the black and white lines (Scopelevel?).

This is one of the most basic tasks and it can be (is for me) a royal pain in the *** - and I haven't even asked about lapping rings...
Thanks,
ian

 

[Guest]

[ 07-12-2003: Message edited by: S1 ]

 

[TiroFijo]

Hola amigos (first post here)

! You have a great site, please allow me to join you to learn more about this fascinating sport.
S1, do you use a scope level for all your scopes, the "clicking" ones and the ones with the R2 reticle?
In your opinion, from what distance does the vertical component of the crosswinds, and the spin (yaw of repose) drift must be taken into account?
I like your idea of the inclined vertical post for the R2 reticle, R.Rinker's book "Understanding Basic Ballistics" mentions that the rear sight in the old Springfield rifle also had a little lateral slope buil-in to compensate for spin drift

.