Ok,

So I go with a friend that has an Accuracy International 300 WinMag 27 inch barrel 1-11 twist, to rearrange the paint on the 600yd gong. Did some paper shooting also after some very unexpected results from both his 300 and my 308-not my 40X. It seems that a week ago Larry was provided info(from a fellow from AI)to load his bullets out to maximum magazine length. His previous OAL was 3.53. New OAL 3.62. Powder charge the same 79gr H1000, bullet same Hornady 208gr A-max, same magnum primer. The difference at 600yds was .6 MOA. The ballistic calculator used previously for range development was based upon chronograph measurements of 2888fps@muz. It showed +3.1 MIL at 600 from 100yd zero. The only way we were able to come up with numbers that matched the range results(+2.5 MIL)was to increase velocity to 3150 in the program. Did he really gain 262fps merely by increasing OAL by .09? The bullet is still not touching the lands.

With my 308 I was shooting RBCD 126gr around 3400 muzzle 5 inches high at 100yds. I expected there to be some drop at 300yds. NIL, Nada, Neitz! Still 5" high at 300. I was able to consistantly ring the 600yd gong by bracketing it with the horizontal and verticle center of the reticle--basically aiming 5"high and 5"left..the wind was blowing about 9.3 mph with gusts to 12.9. My 308 is a Remy 700 Varmint, slightly modified. Barrel cut back to 20 inches. It is 1-12 twist. It was funny how the bullet holes from 308 were oblong at 100yds and perfectly round at 300yds. Am I to assume my 308 was not stabilizing these rounds until they "slowed down a bit"?

It was a most interesting day and it has left both of us shaking our heads.

Anybody got any guess as to what we just witnessed?

Andy

My guess after reading all that crazy schitt, is that you just witnessed the result of Doctors Venkman, Stantz and Spengler crossing the streams!

Seems fairly obvious that since the bullet started out .09 closer to the target, it therefor had less time to drop and thus hit higher on the target. Simple physics.

quote:

Originally posted by drewhenrytnt:
Ok,

The difference at 600yds was .6 MOA. The ballistic calculator used previously for range development was based upon chronograph measurements of 2888fps@muz. It showed +3.1 MIL at 600 from 100yd zero. The only way we were able to come up with numbers that matched the range results(+2.5 MIL)was to increase velocity to 3150 in the program. Did he really gain 262fps merely by increasing OAL by .09? The bullet is still not touching the lands.

Without a chronograph, you will never know. Same temp? Same wind? Same pressure? Same humidity? Same number of shots through the barrel since cleaning? Had the scope turrets been adjusted since the previous time the rifle was shot and are the adjustments precise and repeatable?
Who knows...

quote:

It was funny how the bullet holes from 308 were oblong at 100yds and perfectly round at 300yds. Am I to assume my 308 was not stabilizing these rounds until they "slowed down a bit"?

126gr in a .308? That would be my guess. What barrel twist did you choose for that load?

No mystery there - just a more pronounced effect.

quote:

It seems to have escaped the attention of the Mythbusters and everyone in the forums that bullets do not leave the barrel traveling in a straight line. Upon exiting the muzzle, a bullet yaws considerably, and only after it has flown for some time will it stabilize. In fact, long, heavy bullets, like a .30 caliber, can take hundreds of feet to fully stabilize.

Check this link. " How Bullets Fly ". (It's in English).
http://www.nennstiel-ruprecht....htm#header_stability

The yaw of a 5.56 Nato bullet.


357 Magnum bullet.

quote:

Originally posted by Blacktailer:
Seems fairly obvious that since the bullet started out .09 closer to the target, it therefor had less time to drop and thus hit higher on the target. Simple physics.

I particularly like 303Guy's first Graph for an excellent explaination.