Artillery Rear Sight Offset???

[FNorm]

Being a long range, high power shooter, let's talk ballistics for a minute. Can a 9mm go 800 meters? Sure. Can it do so accurately? Prolly not. I regularly shoot .308 and 30.06 at 600 yds, and a 6.5 X 284 at 1000yds. Planning reloads, you have to keep the bullet supersonic til it hits. Generally 1100fps. Muzzle velocity on the .308/ 30.06 is in the 2500-2700fps range to do this, with a 175-190 gr. bullet. The 142 gr. bullet leaves the 6.5/284 at 3200+. A 9mm 115-125 gr. muzzle velocity is 11-1250?

A bullet that slows to subsonic will start to tumble, and weave around. It is still dangerous, and will do harm. But I think the French Helmet thing was propaganda. Probably worked as the treaty made them stop making artilleries.

FN

[biffj]

Originally Posted by FNorm

Being a long range, high power shooter, let's talk ballistics for a minute. Can a 9mm go 800 meters? Sure. Can it do so accurately? Prolly not. I regularly shoot .308 and 30.06 at 600 yds, and a 6.5 X 284 at 1000yds. Planning reloads, you have to keep the bullet supersonic til it hits. Generally 1100fps. Muzzle velocity on the .308/ 30.06 is in the 2500-2700fps range to do this, with a 175-190 gr. bullet. The 142 gr. bullet leaves the 6.5/284 at 3200+. A 9mm 115-125 gr. muzzle velocity is 11-1250?

A bullet that slows to subsonic will start to tumble, and weave around. It is still dangerous, and will do harm. But I think the French Helmet thing was propaganda. Probably worked as the treaty made them stop making artilleries.

FN

for most rifle bullets there is a definite correlation between the transition from supersonic to subsonic and the tumbling of bullets. It all has to do with stability and long thin bullets which fly well at long distance are not terribly stable when the spin slows and the buffeting of the transonic shockwave starts. That is the biggest cause of the inaccuracy at long range. I've seen the same issues with my long range stuff like the .50 cal and the 20mm. However, for pistol bullets the same doesn't hold quite so true. There is some instabilty at the point where the bullet goes transonic and the shockwave moves back in front of the bullet but it is nowhere near as extreme or destabilizing to the short bullets fired from handguns. I'm not trying to say that the 9mm parabellum is very accurate at 900 yds but its not quite so bad as you seem to think. When we dug bullets out of the sand dune at 900 yds the 9mm bullets had always hit point first and showed some impact damage like having the plating scratched off by the sand at impact. The same was not true of the .223 stuff we fired at the same range. We normally found the bullets lying pointy end toward the shooter and they were so nice and undamaged that they could almost have been reloaded, except for the rifling grooves of course. The 9mm bullets also kicked up a pretty good cloud of sand at that range while the .223's were nearly undetectable. The whole point I'm trying to make here is that the 9mm is not a good round for long range shooting if your intent is to hit a particular target but for "volley fire" type shooting it can be pretty effective and dangerous to the attacker. Accuracy is good enough to get them in the ballpark too....

Frank

[Vlim]

The total range of a 9mm is within the 1200 - 1500 meters, for all I know this is a pretty well-researched fact. So with a total range of 1200 - 1500 meters, I fully expect 800 meters to be feasible and lethal. Of course it will be difficult to hit a target dead center but as said before, the point was to keep the enemy away from the minimum field artillery range and the artillery unit themselves.

The 800 meter 'french helmet' story can be found in the official LP08 manual issued by the German army:

Translation from the manual (1917):
Performance of the Lange Pistole 08.

Due to the high rate of fire and the ease with which it can be handled, the pistol, in combined firing, and with enough ammunition available can be used effectively even against head sized targets up to 600 meters. Between 600 and 800 meters, with the correctly set sights, results can still be expected.

Up to 200 meters, every target can be hit with result in single fire.

At 800 meters a horse skull and a french steel helmet will be shot through.

[FNorm]

biffJ.

Interesting! I never thought about a bullet that's about as long as it is wide. So if it starts a subsonic tumble, the trajectory isn't going to change that much! Almost like a musket ball.

FN

[sheepherder]

Originally Posted by Vlim

At 800 meters a horse skull and a french steel helmet will be shot through.

Is that a single shot, or two separate shots???

Reminds me of the story of Jesse James, when he rode with Quantrill's raiders, lining Union soldiers up against a tree to see how many could be penetrated with one rifle shot...

[Vlim]

two separate shots

(not a lot of horses wore french helmets, back then anyway, lol)

[biffj]

The 9mm bullets don't tumble at that range, they are still going straight even though they drop below the speed of sound at less than 100yds. If simply dropping below the speed of sound caused tumbling than the effective range of the 9mm parabellum would be 80-90 yds. The difference in the effect of passing the sound barrier between these short bullets and the longer rifle bullets is the center of gravity's location in relation to the aerodynamic stability of the bullet. With the short pistol bullets the CG is pretty close to the aerodynamic center and therefore the bullet does not lose much in the way of stability as the shockwave moves forward due to the slowing of the bullet. In the long rifle bullets the CG is frequently quite a way back on the bullet and the CG always wants to be in front. The only thing keeping these bullets going straight is the spin and aerodynamics. As the bullet slows down the shock wave moves forward and that destabilizes the bullet as it moves in front of the CG. This doesn't always lead to tumbling but can cause wobble or nutation as its called. That is what disrupts the accuracy, not tumbling. Sorry for hijacking the thread with ballistics but it is pertinent.....

Frank