Bullet drift?

[BULLET 05]

I was shooting a target at 500 yards with my 6BR. I am using a 87gr Vmax and MV=approximately 3100 fps. 1-10 twist barrell. My question is how much if any will the bullet drift from the spin of the bullet.

 

[Stickler]

Do a search on "spin" drift.

 

[338 dude]

I was shooting a target at 500 yards with my 6BR. I am using a 87gr Vmax and MV=approximately 3100 fps. 1-10 twist barrell. My question is how much if any will the bullet drift from the spin of the bullet.

Download the Shooter app or possibly Applied Ballistics, LLC app put in all your info check the results turn off Spindrift check your results again that should tell you exactly how much it will affect you

 

[JEFFPPC]

Nothing scientific here. But, I have shot a lot at 500yds in the evening with dead conditions with very accurate 6ppcs and 6 BRXs. I think 1 click which would be 5/8 of an inch seems to even things out. Multiple times I have put 1 click of left in and hit point of aim first 3 shots , cloverleaf all bullets touching. When moving to 500 yds from 300 in a match with no sighters I arbitrarily put 1 left click in, then figure what windage I want and then dial it in. Seems to work for me.

 

[chkunz]

Nothing scientific here. But, I have shot a lot at 500yds in the evening with dead conditions with very accurate 6ppcs and 6 BRXs. I think 1 click which would be 5/8 of an inch seems to even things out. Multiple times I have put 1 click of left in and hit point of aim first 3 shots , cloverleaf all bullets touching. When moving to 500 yds from 300 in a match with no sighters I arbitrarily put 1 left click in, then figure what windage I want and then dial it in. Seems to work for me.

This is about all you need to know about wind drift.

 

[expiper]

I was shooting a target at 500 yards with my 6BR. I am using a 87gr Vmax and MV=approximately 3100 fps. 1-10 twist barrell. My question is how much if any will the bullet drift from the spin of the bullet.

 

[expiper]

You need to worry more about what the winds are going to do with that bullet ,,,Roger

 

[mike a]

.43”

 

[biggun2869]

I read an article on it many years ago in precision shooting. Its called the corralis efect. Above my pay grade but I do remember reading about it and what it was called. Really doesn't come into play until VERY long distance is my main takeaway

 

[FeMan]

I read an article on it many years ago in precision shooting. Its called the corralis efect. Above my pay grade but I do remember reading about it and what it was called. Really doesn't come into play until VERY long distance is my main takeaway

Spin drift and coriolis effect are not the same thing. Coriolis has both vertical and horizontal components but is negligible at the ranges most of us shoot. I love shooting matches in switchy head winds where people don't dial spin drift

 

[JEFFPPC]

FeMan, please explain your comment on switchy winds which I do not view the same as a headwind. All wind has a vertical component readily visible with a vertical probe.

 

[FeMan]

FeMan, please explain your comment on switchy winds which I do not view the same as a headwind. All wind has a vertical component readily visible with a vertical probe.

Sure. I am talking about horizontal deflections from spin and wind.

I shoot at Sac Valley and there are head winds that move from 10:30 to 1:30 in the fall. In a dead wind condition, most of our rifles will shoot 7 to 8 inches right at 1k, which equates to a 1.5 mph or so left wind. Although I shoot some F Class, I shoot primarily tactical, so when the targets come up you have to shoot the condition and you don't get spotters. For those that don't dial spin drift, in those conditions where shot 1 is left wind, shot 2 is straight up, and shot 3 is a right wind, they are all over the place because they are unknowingly mixing feedback from wind drift and spin drift.

 

[JEFFPPC]

Ok, I would just call that 3 different conditions . If you don't hold accordingly you will not get good results.I would think the spin drift is very minor compared to what you will get from a 2 or 3 mph wind drift. So if you had 4 in of wind drift say coming from 11:30 to 5:30 how much would you add for spin drift on top of the 4 in .?

 

[FeMan]

For that condition, I would hold about 5.5" at 1k. If it were coming from 12:30 to 6:30, I would hold 2.5" (combining wind and spin). Once you have a condition it doesn't matter since spin is a constant. Its when it adds to one shot and deducts from another and you are calling it all "wind" that it will get you.

 

[expiper]

this has turned into a "windy" post,,,Roger

 

[johara1]

Tell me what kind of groups your rifle shoots at 100? a .1 or .250 or a .5? ... If it isn't a .1 you don't need to worry about spin drift, the wind will take them for a ride do to inaccurate rifle..... jim

 

[rwj]

Is spin drift dependent on whether the rifling is right or left hand twist?

 

[JEFFPPC]

For that condition, I would hold about 5.5" at 1k. If it were coming from 12:30 to 6:30, I would hold 2.5" (combining wind and spin). Once you have a condition it doesn't matter since spin is a constant. Its when it adds to one shot and deducts from another and you are calling it all "wind" that it will get you.

Ok so this wind coming from the right as opposed to coming from the left is only baically half value. Do I understand this correctly. If I do then what if this wind was 3 to 9 versus 9to 3?

 

[FeMan]

Ok so this wind coming from the right as opposed to coming from the left is only basically half value. Do I understand this correctly. If I do then what if this wind was 3 to 9 versus 9to 3?

I screwed up my math above, my spin drift at 1k is 0.75 moa, or 7.5 inches roughly and not 1.5" .

For the 3 oclock or 9 oclock scenarios, the spin drift gets blended into the numbers and ignoring it works fine in most disciplines. But if I have to make a cold bore shot at 1,300 yards, my spin drift is about 12 inches. If I don't calc that in along with the wind, I am that far off to the right. If I get to shoot sighters and walk it in, it doesn't really matter. In tactical and ELR you really need to center up on shot 1 so its a necessity.

 

[moondog]

Is spin drift dependent on whether the rifling is right or left hand twist?

Yes