Example Question
Using identical shell spec. fired out of the same rifle other than using 2 different powders.

One powder impacts bullet directly into bullseye.
The other powder impacts bullet 1" above bullseye.

Which powder is producing the most velocity at this 100yd bullsye?I think Im allowing this to be too confusing?

No way to tell without a chronograph. The point of impact at 100 yds has nothing to do with the velocity, it's more dependant upon the harmonics of the combination. Now at say 800 yds obviously a lower muzzle velocity will produce a lower point of impact due to more bullet drop.

As previously stated there is no way to tell by point of impact at a single distance.If you sight one in dead on at 100 yards them shoot it at 300 yards then do the same with the other load,the one that groups highest on the target at 300 yards should be the highest velocity.

[ 06-29-2003, 01:53: Message edited by: stubblejumper ]

Boltman is correct... If you shot both of those loads at say 800 yards the slower one would hit lower...BUT you would also have to figure in the fact that one of the loads hit 1" higher at 100 yards. One inch at 100 equals @ 1MOA[minute of angle]...1 MOA at 800 yards equals @ eight inches.
Thus one of those loads already has 1 minute of up already dialed in.

Explainations all make sense.Thanks for assistance in squareing up my ears.

All correct answers. Think of it this way: slower bullets stay in the barrel longer, and a rifle starts recoiling while the bullet is in the barrel. The slower bullet will have the barrel pointing a little higher on departure.

There is also something called "muzzle whip". This is the harmonics part. If the bullet is exiting the muzzle when the barrel is "whipping" up, the bullet will be "thrown into the air" (please forgive the scientific terms). I believe this was the explanation of the 303 Brit SMLE hitting higher than any calculation predicted. If the bullet leaves the barrel with upward momentum, and the next one leaves the barrel with downward momentum, the down range points of impact cannot used to calculate velocity accurately.

HTH, Dutch.

Thanks all,
I guess an example of this was when I tested for a good powder for my new rifle. Same bullet and all case spec the same. Two of the four groups registered 150 fps more than the other two but the point of impact was so close you could stack the four targets and make a pretty nice 16-shot group for a starting round.
May all your groups cut one hole!

Ray, I was thinking of 130, 140 and 150 grain bullets out to 400 yds relative to bullet drop, and velocity. You are right, the 30-06, 270 are fine cartridges. I also cut my teeth with the 30-06, went to a 270 after about 20 years because I got bored with the 06, then I got bored after 20 some odd years with the 270, and went to the 7 mag. I primarily chase muley's so the 150 grain bullets suit me best. But my 30 inch 5x4 didnt like my 130 grain Sierra Boattail out of my 270.
Take Care

Plain Drift:

I chronograph a lot of loads. I have noticed that two loads can have the same velocity and same bullet, case, priimer etc, just different powder and have very different points of impact.

Not being an expert, so just using some educated logic. I also notice that two different powders can produce the same velocity, but yet one have more felt recoil than the other. I am sure this has to do with how the pressure curve builds up during powder ignition. Also toss in the rate of twist on a barrel having a certain effect on point of impact.

I have noticed that two loads can be compared in two rifles with the same everything and have a different point of impact based on the twist being different in the two.

Not an explanation. Just some more experience and observations. I have wondered the same questions and this is what has happened on my quest for an explanation to it.