Wind drift? How much does your bullet move?

**RobaloSunrise** · #1 01-20-2012, 09:34 PM

Another good article.

http://www.accurateshooter.com/shoot...t-vs-distance/

V/R
J

**Wolf6151** · #2 01-20-2012, 11:59 PM

**** I knew I should have paid attention in Algebra. This gives me a new found respect for the guys who shoot 1000 yd. competitions. Where do you get these come up sheets the article refers to? I assume they would be for each individual bullet at different velocities?

**RobaloSunrise** · #3 01-21-2012, 08:00 AM

You get them through time and practice. There is no substitute for your own dope books.

V/R
J

**THE JAMMER** · #4 01-21-2012, 06:22 PM

EXCELLENT ARTICLE. I have used ballistic software for many years, but that article was probably the best "layman's explanation" I have ever read.

WEll done Robalo. You've been doing some great stuff lately. I have been out of pocket for a while with rotator cuff, and am now wading through the stuff on canting. I've used levels on my scopes for years as well, but what I've read so far gives great geometric explanation of the phenomenon.

THE JAMMER

**CHARLIE** · #5 01-23-2012, 12:03 PM

Also heavier bullet less drift.

Jammer hurry back you have been gone too long

**RobaloSunrise** · #6 01-23-2012, 12:29 PM

Heavier bullets do not always drift less. Bullets with a higher BC drift less. 142 gr 6.5mm VLD's drift considerably less than 180gr 7.62mm flat base bullets do. Even though they weigh less.

V/R
J

**CHARLIE** · #7 01-23-2012, 02:40 PM

Could have to do with more time exposure to the wind ya think ??

**RobaloSunrise** · #8 01-23-2012, 02:53 PM

Quote:

Originally Posted by CHARLIE

Could have to do with more time exposure to the wind ya think ??

You are right if you are referring to the differences in velocity between what a 6.5 x 284 could produce and what a 308 would produce. However if you adjust velocities for each until they are the same say 2900fps which is attainable by both 6.5x 284 and 300 win mag the lower BC of the 300 is greatly trumped by the high BC 6.5. When shooting distance it is all about BC. If you can push a .700BC bullet at 2800fps it will outperform a 400 BC bullet at 3000 all day long in both elevation and windage.

V/R
J

**RobaloSunrise** · #9 01-23-2012, 03:22 PM

Ran it through my ballistics program and at 2900fps a 180grn 7.62 with a G7 profile of .202 has a drop of 35.56moa (372.34") and a drift of 11.96moa (125.28") at 1000yds with a 10mph wind from the 9oclock. At 2900fps a 140grn 6.5 with a g7 profile of .293 has a drop of 26.83moa (281.01") and a drift of 7.42moa (77.72") at 1000 yds with a 10mph wind from the 9oclock. About 2/3rds the movement. The 7.62 will have a longer flight time due to the increased drag and quicker deceleration which is due to the lower BC. So yes a longer flight time does effect the outcome but only due to the BC, if you use a higher BC 7.62 bullet then the results are the same as the 6.5. A 200 grn 7.62 vld at 2900 is getting close to the same as the 6.5 and a 205 grn should be almost the same.

V/R
J

**CHARLIE** · #10 01-23-2012, 04:33 PM

A heavier bullet with the exact same everything and velocity will drift less with the wind than the lighter bullet. I have a question, are you saying that the lighter bullet will maintain velocity longer than a heavier bullet of the same design ?? My thoughts are that the heavier bullet will surpass the lighter bullet at longer ranges. The lighter bullet will lose velocity quicker.. and at some range the heavier bullet will surpass the lighter bullet.

Please do not get me wrong I am certainly not a know it all its just from years of being involved in the shooting game.. Have no access to programs or charts or tables.. just my thoughts..