Ballistics question

[johnf]

The only place for me to shoot long distances is at my dad's place up on a mountain. Our longest shot is about 400 yards. I've only tried out to 300 so far and we shoot from 1 ridge into the side of a mountain accross a little draw.

When shooting passed 100 yards we have to back up on the the ridge and shoot up to the target. At 300 yards the target is 50+ feet higher than we are.

My scopes on my 243 and 25-06 are identical Nikon prostaff 3-9X40 set at about 1 3/4" high at 100 yards. Both guns shoot sub moa at 100. At 300 yards shooting up hill neither guns shoot low. The 243 shoots right where I'm aiming, which means 1 3/4" low of the 100 yard POI and the 25-06 actually goes about 2-3" high at 300 yards which is above the 100 POI.

I don't think I'm pulling up, and they do it on every shot.

Is this some wierd up hill ballistic thing, or do you think maybe I'm pulling up and don't realize it?

[AJ]

Re: Ballistics question

There are a couple of possibilities here. Assuming that your .243 Win is using a standard deer load of a 100 gr bullet exiting about 3000 fps, zeroed 1.75" high at 100 yards. If your scope's centerline height is about 1.5" above the bore celterline, your bullet should be about 6" low at 300 yards.

1. If your bullet is hitting dead on, I think you need to measure your range with a range finder, or you are shooting up a very steep hill. You may find that your actual horizontal distance is only just over 200 yards. If the 25-06 is shooting 2-3" high at 300 yards, there is a big problem. It should be similar to the 243's trajectory.

2. The front rest is different. If your front rest for the 300 yard shots is harder than the front rest for the 100 yard shot, it will make the bullet's impact higher. This could make the difference.

3. You had a strong tail wind while you were shooting.

4. Arkansas gravity is different than everywhere else.

[johnf]

Re: Ballistics question

I was using the bushnell yardage pro that I got from bigmoss.

With the 25-06 we were shooting off a round bail of hay. With the 243 I was shooting prone (the hay has been eaten)

I did change loads with on the 25-06 and they were shooting higher with the new load. I think that would have made that much difference.

The wind up here is pretty funky. Today it was coming straight over the mountain and swirling around in all directions. It was coming out of the S where I was shooting from so I aimed about 6" to the left to compensate. When I got to the target the wind was almost at my back. I don't know if that's a constant thing caused by the mountain, or if the wind shifts. Maybe I should set some ribbons up about every 50 yards to see what it's doing.

The draw between the ridge and the mountain probibly drops about 20-30 feet so from the spot that I shoot at 300 ground level goes down and then way back up. That probibly does some weird things with the wind. But I had a 4 shot group at 300 that measured just under 3", so I have a hard time believing the wind was blowing it alot.