Windage and Round ball drift

[AZ hunter]

Does anyone have a windage chart or calculation that can be used to estimate the amount of drift a round ball will have at differant loads and distances? I have a 4H group going to Kerrville TX this summer to shoot in the 4H national invitational and with the spring winds they are having trouble getting good scores on the target. They are all shooting 50caliber slow 1 in 60 twist 32in rifles. We have been shooting 40gr of FFF at 25 and 50 yards and then bumping up to 60gr FFF to shoot the 77 and 100 meter silhouetts. I am getting around 20 to 25 inches of drop between the 25yard and 100meter targets and can adjust that with the sites. But the wind is drifting their round balls 25inchs plus off the target. Any suggestions or information would be greatly appreciated.

Thanks DCM

 

[biliff]

A very generic/across the board rule of thumb is one inch of drift at 100 yds for every mph of crosswind.

Pulled this from the forums links section. Hope it helps some. http://www.ctmuzzleloaders.com/ctml_experiments/rbballistics/rbballistics.html

 

[BrownBear]

I can't find my copy at the moment, but isn't this info in the ballistic tables of the Lyman manual. Memory is frail, but that's my best recollection.

 

[AZ hunter]

That is great thank you

DCM

 

[AZ hunter]

We just perchased a new Great Plains so I will look in that manual. Thanks

DCM

 

[tg]

I would bump the powder charges up for one thing that load at 100 yds is more subject to drift/drop than a 90-100 gr load, definately worth a try.

 

[Zonie]

To get a feel for wind drift and powder loads I ran my roundball ballistic program with velocities that a .50 would give for the powder loads you mentioned.

The Lyman Black Powder Handbook says a .50 with a 1:48 twist would be around 1200 fps for the 40 grain powder load and around 1370 fps for the 60 grain load.

For the 40 grain load I get the following drift.

5 MPH crosswind
50 yd = 1.4", 70 yd = 2.5", 100 yd = 4.1"

10 MPH crosswind
50 yd = 2.7", 70 yd = 5.1", 100 yd = 9.9"

15 MPH crosswind
50 yd = 4.1, 70 yd = 7.6", 100 yd = 12.2"

For the 60 grain load drift

5 MPH crosswind
50 yd = 1.6", 70 yd = 3.2", 100 yd = 4.9"

10 MPH crosswind
50 yd = 3.2", 70 yd = 6.0", 100 yd = 11.4"

15 MPH crosswind
50 yd = 4.9, 70 yd = 9.0", 100 yd = 17.1"

Note that the wind is assumed to be blowing directly across the line of fire.

You might also notice that the larger powder load and its higher velocity causes more drift at each distance.
I'm not sure what the exact cause of this is but it may have to do with the supersonic/sub-sonic velocity loss.

The drift vs velocity got my curiosity going so I ran the program with the velocity that Lyman says a 90 grain 3Fg powder load gave them in the same .50 caliber barrel.

For the 90 grain load (1830 fps) drift

5 MPH crosswind
50 yd = 1.5", 70 yd = 3.0", 100 yd = 6.2"

10 MPH crosswind
50 yd = 3.0", 70 yd = 6.0", 100 yd = 12.3"

15 MPH crosswind
50 yd = 4.5, 70 yd = 9.1", 100 yd = 18.4"

 

[smo]

I have heard from one of the guys i shoot with that depending on wind direction has alot to do with how much drift or drop a ball has.I was told shooting into a head wind will cause more drop, due to the spin on the ball from the rifling. A tail wind would not cause as much drop.10 mph cross wind from l to r would cause a drift and drop to the right, where as a 10 mph wind from r to l would cause the same amount of drift but not as much drop due to the rotation of the ball. :idunno: Has anyone else ever heard of this of expierenced this? Is this a fact or just :bull: :idunno:

 

[MikeChapin]

It makes sense that a headwind will tend to slow the ball down faster giving it more time to drop and a tail wind will give it a boost to keep its velocity and cross the distance a little faster.

Wind out here is a concern at many places I shoot. You end up getting where you can read the wind and hold where you need. In February I was at the winter challenge. At 200 yards I held on the 5 ring on the target to the left of mine to put four on my target. For 100 yards I was holding on the right side of the black and it wasn't enough. All five scored but they were all off to the right.

Mostly it is a guess at how much to hold for the wind. The guess comes from experience.

At 25 and 50 yards any wind effects are usually from the wind pushing my body around. Any effect on the ball is usually lost in my own body motion.

 

[AZ hunter]

4H rules limit them to 60gr max

Thanks Zonie I will set up a crono to see what there volosity is.

The information from all has been great

Thanks DCM

 

[Tom Compton]

Enough wind today to aim at one target and the next one over. Shot at Brady TX for a while and some folks did just that - put up a sighter target and on the adjoining frame was their score target.

If 4H rules allow, make some wind flags and experiment. Place one 5-10 yards from the firing line, others at about 40, 60 and 80 yards.

A quartering wind has about 1/2 the drift as a 90* wind of the same velocity.

Drop me a PM about location and dates, I might be able to visit.

Good luck

 

[AZ hunter]

I will be setting flags and have purchased a wind meter to aid in their training. thanks

Unsure how to send PM but the dates are June 28th thru July 2nd in Kerrville.

Thanks again

DCM

 

[dbutch]

This last week I was shooting a 54 cal at 100 yards cross winds were 25 to 30 mph with gusts..getting 0-13" drift with a 90 gr. load...I'm thinking you are going to need to find a windy day and do some hands on tests to be accurate on these stats.

 

[AZ hunter]

This last Sunday we were shooting in about the same amount of wind in-between snow showers and getting about 20 - 25 inches of drift. We again are shooting 50 caliber with 60 grans of powder.

Thanks agian for all the help.

DCM

 

[dbutch]

20-25" wow how are you going to chart that?
Courious what a hotter load would do? less or more drift? Good luck with your testing ..very interested in your results.

 

[Gotspark]

I shot some today,it was very windy. The grass is about 10-12" tall on the bank and most of the time it was laid down and looking shiney white. The shots were hitting 3 1/2" to the right at 50 yds 70grain load, surprisingly the groups stayed at 1 3/4" outside to outside. I went to see what a larger load would do to my groups, didn't work out to well but it wasn't a total loss, got to see what the wind will do to round balls.

 

[Dave Rosenthal]

Just remember if you switch to conicals or Maxi's, the numbers might change as far as the drift goes. One of the reasons that I choose to shoot .50 cal 370 grain T/C Maxi-Balls on occasion is to overcome wind as an obstacle, especially at 100 yards. Those heavy conicals seem to be a little less affected by the wind. With 72 grains of 3Fg Goex, a pre-lubed wonder-wad and the 370 grain T/C Maxi, the chrono says it goes out the tube of my 28" barreled Lyman Trade Rifle at 1349 FPS.

At 60 grains you'll get less recoil and a little less speed. Does the 4H say round ball only?

Good luck with the wind! Mother Nature is unpredictable :haha:

Dave