When shooting way out there does the twisting of your bullet from the rifling in your barrel need to be taken into account?

It's called "spin drift".

Bullets tend to drift to the right. My ballistic program account for this and is reflected in hold-off values

quote:

Originally posted by Randy Routier:
When shooting way out there does the twisting of your bullet from the rifling in your barrel need to be taken into account?

Youneed to shoot your bullet on a calm no wind day and measure any spin drift that you may have. This can then be imputed into the Exbal program that I use

I do not use any spin drift for the 300 grain SMK in my 338 Lapua. I know several others that do not use any spin drift for this bullet either.

Yeah, I can't say it's something that has so much affect on bullet flight that it's noticeable.

I believe you would have to be shooting WAY past 1k before you need to start worrying about it. WAY WAY past.

Alan

quote:

Originally posted by GSSP:
I believe you would have to be shooting WAY past 1k before you need to start worrying about it. WAY WAY past.

Alan

Depends on the rifle and the bullet in my experience

Thanks guys.

Does it matter if you have right twist or left twist rifling and if the wind is from the right or the left?

Drew, there are very few firearms with a left hand twist. Colt revolvers are the only one that come to mind at the moment.

Remember spin drift is realitive, so a spin drift adjustment is in addition to any windage and elevation adjustment.

I can see it a little bit in my rifles, but not much. If i remember correctly, for me it's like 1/4 MOA at 500 yards....if that.

When I zero, if in doubt, I leave it an extra click to the left and figure I have the spin drift covered out to at least 500 yards.

quote:

Originally posted by jwp475:
You need to shoot your bullet on a calm no wind day and measure any spin drift that you may have. This can then be imputed into the Exbal program that I use

I do not use any spin drift for the 300 grain SMK in my 338 Lapua. I know several others that do not use any spin drift for this bullet either.

Good answer! Get a good ballistics program and practice at ACTUAL RANGES.

You'll find out that there are "bigger fish to fry" than worrying about spin drift (gyroscopic drift). Like learning to read the wind etc.

quote:

Originally posted by DaMan:

quote:

Originally posted by jwp475:
You need to shoot your bullet on a calm no wind day and measure any spin drift that you may have. This can then be imputed into the Exbal program that I use

I do not use any spin drift for the 300 grain SMK in my 338 Lapua. I know several others that do not use any spin drift for this bullet either.

Good answer! Get a good ballistics program and practice at ACTUAL RANGES.

You'll find out that there are "bigger fish to fry" than worrying about spin drift (gyroscopic drift). Like learning to read the wind etc.

I would worry about canting before I would worry about this.

quote:

Originally posted by jwp475:

quote:

Originally posted by GSSP:
I believe you would have to be shooting WAY past 1k before you need to start worrying about it. WAY WAY past.

Alan

Depends on the rifle and the bullet in my experience

I'll take "your" word on that topic.

Alan