I've been down in TX visiting the world's greatest grandkids. Aaaaaand I stopped off at a couple of casinoes on the way back.

Back on task: Lord knows one can't argue with a computer program. It tells the armchair bwanas all they want to know. And you can generate those way-kewl drop charts to tape to your stock to show everyone that you're a dyed in the wool box-a-year shooter. All I can say is it works for me. YMMV

quote:

All I can say is it works for me.

Great....if it works for you.....but it's still dead wrong!

It is worth shooting your rifle at the ranges you intend to use it in the field. I plugged all my numbers into the various computer programmes and while it was an interesting and useful guideline is was some way off compared to actually shooting the bullets at paper at various ranges.

My 308W is 2 inches high at 100, a fraction high at 200 and about 12 inches low at 300. None of the computer programmes put me anywhere near that low at 300.

quote:

Originally posted by caorach:
My 308W is 2 inches high at 100, a fraction high at 200 and about 12 inches low at 300. None of the computer programmes put me anywhere near that low at 300.

I have little doubt of this but please tell me what numbers you used for:
1. Ballistic coefficient
2. Muzzle velocity
3. bullet weight
4. -0- range
5. sight height above bore

I'd be happy to check this for everyone to see if my "calculator" is off!

vapodog

quote:

I have little doubt of this but please tell me what numbers you used for:
1. Ballistic coefficient
2. Muzzle velocity
3. bullet weight
4. -0- range
5. sight height above bore

I'd be happy to check this for everyone to see if my "calculator" is off!

Try these numbers with your calculator and see what you come up with.
> .257 Sierra GameKing
> 117 grains
> .410 ballistic coefficient
> 1.5" sight line
> 3,300 fps muzzle velocity
> zero=100 yds (sighted in dead on at 100 yds)

My calculator says the projectile will be -0.4" at 50 yds and -7.3" at 300 yds. Most calculations I performed on other projectiles/velocities/etc had the bullet above the line of sight at 50 yds. That's why I gave the answer I gave earlier.

For example:
> 10MM
> 180 gr
> .140 ballistic coefficient
> 1.5" sight line
> 1,800 fps muzzle velocity
> zero=100 yds (sighted in dead on at 100 yds)

My calculator shows the trajectory to be +1.0" at 50 yds. Dead on at 100 yards. -17.8" at 200 yds.

To be honest, though, I have not checked any of this out specifically at the range. I've just been running numbers as a result of this thread.

I think I'm learning something--don't trust a computer program alone, go to the range and actually see what is going on.

P.S. As a sort of side note: When I was a young man, my father-in-law taught me to sight in rifles at 28 yds and he said they'd be where they need to be at 100 yds. This was with open sights (no scopes). Was this good advice?

quote:

Try these numbers with your calculator and see what you come up with.
> .257 Sierra GameKing
> 117 grains
> .410 ballistic coefficient
> 1.5" sight line
> 3,300 fps muzzle velocity
> zero=100 yds (sighted in dead on at 100 yds)

at the muzzle.....-1.5
at 25 yards.......-0.8
at 50 yards.......-0.3
at 75 yards.......00.0
at 100 yards.......0.0
at 200 yards......-2.2
at 250 yards .....-4.9
at 300 yards......-8.8

Sure wouldn't argue much at 1.5" difference at 300 yards.....

quote:

> 10MM
> 180 gr
> .140 ballistic coefficient
> 1.5" sight line
> 1,800 fps muzzle velocity
> zero=100 yds (sighted in dead on at 100 yds)

at 25 yards.....+.2"
at 50 yards....+1.0
at 75 yards....+1.0
at 100 yards....0.0

quote:

Originally posted by jsl3170:
gents:

if one wishes to have a rifle sighted dead on at 100 yards, then where will the bullet be in relation to the bullseye at 50 yards; high, low?

thanks.

Jeff

Here's the original post and I did know that jsl3170 has a left handed M-70 in a (IIRC) magnum so the velocity was much more applicable to the 2800 FPS range instead of a .44 Mag in the lower velocity.

quote:

Originally posted by vapodog:
I have little doubt of this but please tell me what numbers you used for:
1. Ballistic coefficient
2. Muzzle velocity
3. bullet weight
4. -0- range
5. sight height above bore

Am in work so from memory:

1. .338 (Hornady spire point)
2. 2950
3. 150 grain
4. 220
5 1.75 inches

The computer seems to give a drop at 300 of about 6 - 7 inches for this load. I actually see a drop of about 11 - 12 inches so enough of a difference to be important on the sika deer I shoot. I've never shot it beyond 300 as I'm not going to be shooting game out there but the figures out to 200 - 250 yards seem pretty good.

Go with what the gun says not the computer.
Not all ballistic coefficients are measured
by firing.
Good luck!

quote:

Originally posted by caorach:

quote:

Originally posted by vapodog:
I have little doubt of this but please tell me what numbers you used for:
1. Ballistic coefficient
2. Muzzle velocity
3. bullet weight
4. -0- range
5. sight height above bore

Am in work so from memory:

1. .338 (Hornady spire point)
2. 2950
3. 150 grain
4. 220
5 1.75 inches

The computer seems to give a drop at 300 of about 6 - 7 inches for this load. I actually see a drop of about 11 - 12 inches so enough of a difference to be important on the sika deer I shoot. I've never shot it beyond 300 as I'm not going to be shooting game out there but the figures out to 200 - 250 yards seem pretty good.

I am becoming more and more convinced that the only way to REALLY know what your bullet is doing out at 300 yards and beyond, is to shoot them that distance.

If you plan on taking a shot that distance at a trophy of a lifetime, you sure need to KNOW what your projectile will do.