SmallCaliberCentral

So I was looking at Federal's 204 ammo data, and it show that their ammo loaded with 39gn sierra SBKs has a much flatter trajectory than their ammo loaded with 32gn speer bullets, and is a tad flatter than the Nosler 32's.

Any thoughts? Is this a boo-boo in their data, or is it perhaps that the 39 SBK's have a much better BC??

I never totally trust the drop data as listed on ammo boxes. My real world results too often differ.

I got the data from the ammmo selector on their web site... which I'm sure is the same as what is on the boxes. Nice graphics anyway.

Here's the graph. The SBK is in blue and the other two colors are the Nosler and Speer 32's. I'd say 15" drop over 500y is pretty huge, especially since the SBK is the heaviest bullet...

[img]http://i906.photobucket.com/albums ... .jpg[/img]

i am preety sure it is due to the higher B.C of the 39gr SBK

Bryan Litz addresses this in his book on long range ballistics. The lighter/lower BC bullet ordinarily will shoot flatter at the shorter ranges but, at longer ranges, due to its higher BC, sometimes -- and I emphasize sometimes -- at extended ranges the heavier bullet will have the flatter trajectory because the lighter bullet has begun to slow so rapidly.

That doesn't prove that Federal's data is right, just that it's not impossible. And .204 bullets are so light in general, it makes sense the lightest .204 projectiles would experience this.

(rapid slowing, is that an oxymoron, ...like pretty ugly?)

Now then... understood!

+1 what fred said. In fact I have not seen any ballistics chart showing that any bullet lighter than the 39SBK being flatter shooting. Every rifle caliber has an "optimum" bullet weight/BC for the flattest shooting in a given range. Put it like this..........if you had a ping pong ball that was exactly the same size as a golf ball and you tried to throw them both as far as you could, which would go farther? Of course the golf ball---it's weight will keep it going but the ping pong ball will fall off drastically due to it's low BC (or weight).

makes sense...

RoadKill wrote:I never totally trust the drop data as listed on ammo boxes. My real world results too often differ.

The drop data shown by the companies, of course, is with their test and rifle. The only way to know what your rifle/weapon is doing, is to test your weapon and the ammo/bullet. Varibles are always there. i.e. scope mounting, barrel hamonics, etc. your load and bullet may be way different. Have fun and go make your own drop tests. Bill K

That I do!