Long range 22 - spin drift

F

fljp2002

Regular
Rating - 100%
15   0   0
Location
Moncton
Fellows

Been playing with a ballistic app and noticed that as you increase range the app starts to give correction for drift.

Being new to longer range shooting it was not something I was thinking about. Does anyone have a resources that explain this.

I have been looking at wind but never taught about the spin drift effect
 
Spin drift, also known as gyroscopic drift, is less of a concern for .22LR rimfire shooters than it might be for long range shooters. It's the same for every shot at a given distance so zeroing will account for it. When distance increases the drift will increase. But for .22LR it is less significant than the influence of variation in bullet drop due to inconsistent MV and the effect of wind and other atmospheric conditions such as air pressure and humidity.

For more details see h t t p ://closefocusresearch.com/external-ballistics-summary#Long_range_factors
See also the discussions here h t t p s ://www.rimfirecentral.com/forums/showthread.php?t=391922&highlight=spin+drift and h t t p s ://www.rimfirecentral.com/forums/showthread.php?t=547161
 
Buddy and I were pushing our 22lr precision rifles out to longer distances on paper. I was zeroed for 100m, used Strelok free version (no spin drift capability), it gave me a 200m dial, I used that and was close. Then I adjusted my Strelok settings to true the Strelok calculation for those 200m results. Then I put in 300m in Strelok, and I shot 10 shots at a 1.5' x 1.5' paper target at 300m. I had zero hits on target and one edge hit on the right side masking tape that was holding target up.

Buddy used Strelok Pro, which factors in spin drift. His vertical calculation was same as mine, but it gave him 0.4mil left correction at 300m. He had 10 shots on paper. And I think if I had dialed in 0.4mil left, I would also have had hits on paper. So it makes a big difference in 22lr once you get past about 200m. 0.4mil at 300m is 12cm.
 
I think spin drift is similar to aerodynamic jump or perhaps part of that effect.

Most people think wind drift causes a bullet to impact to the down wind side of the point of aim, but they don't realize there is a vertical offset as well.

Wind from the left causes the round to hit low and right

Wind from the right causes the round to hit high and left.

Think of this as a line from 10 o'clock to 4 o'clock…. Not 9 to 3.

To your point, we were shooting a steel plate with a Vudoo 22LR from 372 yards a couple days ago and it needed .38 mil for spin drift at that distance.

Got 9 out of 10 hits on a 16 inch plate from 372 BTW on video too. Might have got all of them if we weight sorted the ammo and sorted by rim thickness.
 
Last edited:
Spin drift is literally, the change in the flight path due to the spinning of the bullet. It is predicatable and consistent but can vary from type of bullet.

Simple rule of thumb in rimfire and RH twist barrels, 0.1mil left for each 100yds traveled... then factor in the wind. Given how much the ammo disperses at distance and how much it will be affected by the air, you don't need to be anymore precise then this.

So if shooting at 300yds, dial 0.3mils left BEFORE worrying about what the wind dope should be....KISS

Jerry

PS... please note, that this is based on a dead center 50yd zero. You can do the same if running in meters.. 50m dead center, 0.1mils for each 100m going out.
 
Last edited:
^^^ Thanks for the info... Learn something new everyday. I always wonder why I'm hitting to the right at 300 yards with very little to no wind when zeroed at 50 yards.

48178960351_c980694248_k.jpg
 
You must log in or register to reply here.
Back
Top Bottom