Do AR-15 Heavy .224 Bullets Need To Be Single Shot?

[Gunner3456]

Yet the choice of bullets for precision shooting is almost always a bullet with a center of mass purposely moved back by by making it a hollow point. Match bullets have no requirement in the traditional sense, expansion in game animals, it's done to enhance their stability. Go figure.

Fast bullets are supersonic and have a shock wave cushion in front of them in a way that the nose doesn't really contact the solid air. The base of the bullet on the other hand has the air collapsing onto it. When a jacketed bullet is formed either the base or the nose will be open because the jacket is punched and formed from one piece of copper. The perfection of the base of the bullet has far more affect on accuracy than does the nose due to that air collapsing on it.

Match bullets are "hollow point" only for that reason. With the base being fully jacketed it can be precise. If lead were exposed at the nose as with hunting bullets, it would be far less concentric and smooth than if it's left back a little, and only the copper is exposed and accurately formed. Leaving the nose open allows the base to be solid copper which can be precisely formed, and that's where accuracy is most affected.

When a pointed supersonic bullet is in flight, it doesn't even "know" it has a point. The drag on the back from the air collapsing onto it (along with the fast spin) keeps the bullet going straight instead of yawing.

Put even a small nick on the back corner of a bullet and it will lose its accuracy. Not so much with a small nick on the front.

PS This is why the relatively rough exposed lead on the tip of a hunting rifle bullet doesn't much affect accuracy.

 

[deadshot2]

Fast bullets are supersonic and have a shock wave cushion in front of them in a way that the nose doesn't really contact the solid air. The base of the bullet on the other hand has the air collapsing onto it. When a jacketed bullet is formed either the base or the nose will be open because the jacket is punched and formed from one piece of copper. The perfection of the base of the bullet has far more affect on accuracy than does the nose due to that air collapsing on it.

Match bullets are "hollow point" only for that reason. With the base being fully jacketed it can be precise. If lead were exposed at the nose as with hunting bullets, it would be far less concentric and smooth than if it's left back a little, and only the copper is exposed and accurately formed. Leaving the nose open allows the base to be solid copper which can be precisely formed, and that's where accuracy is most affected.

When a pointed supersonic bullet is in flight, it doesn't even "know" it has a point. The drag on the back from the air collapsing onto it (along with the fast spin) keeps the bullet going straight instead of yawing.

Put even a small nick on the back corner of a bullet and it will lose its accuracy. Not so much with a small nick on the front.

PS This is why the relatively rough exposed lead on the tip of a hunting rifle bullet doesn't much affect accuracy.

Can you explain the superb performance of he Lapua D46 that has an open base?

As for the Point of the bullet being inconsequential, look at this picture of a .308 bullet in flight.



You will notice that the bullet definitely has its "nose in the wind". Many long distance shooters will use a meplat uniformer on their bullets to make sure that the nose doesn't cause the bullet to "steer" off course. Others will use a Whidden Pointing die to make the "nose" as perfect as possible.

As for the "drag" from collapsing air, the "collapse occurs far behind the bullet as long as it remains supersonic. Perhaps an issue for bullets that go from supersonic to trans-sonic speeds while in flight but all my rifle rounds remain at either above Mach 2 or close to it though their flight to the target. Likewise for all those shooting long distances up to 1,000 yards.

 

[Gunner3456]

Can you explain the superb performance of he Lapua D46 that has an open base?

Sure. It is a proprietary design that has a step well ahead of the base to shed wind away from the base, and superbly shaped edges at the back.

As for the Point of the bullet being inconsequential, look at this picture of a .308 bullet in flight.



You will notice that the bullet definitely has its "nose in the wind".

There is always a small cushion pushed ahead in supersonic flight. That doesn't mean it's thick enough to see it in that pic.

Many long distance shooters will use a meplat uniformer on their bullets to make sure that the nose doesn't cause the bullet to "steer" off course. Others will use a Whidden Pointing die to make the "nose" as perfect as possible.

I didn't say, especially in competition, that the shape of the nose isn't important. I meant to imply that it doesn't have as much affect as a deformed base would, even pointing out that for long range hunting purposes, the exposed lead nose of a hunting bullet doesn't make it so bad that you can't make a 500 yard kill with it. In fact, I pointed out that the reason there is a hollow point in many competition bullets is only to avoid having the roughness of the lead exposed. Big difference between hunting accuracy and competition accuracy.

As for the "drag" from collapsing air, the "collapse occurs far behind the bullet as long as it remains supersonic. Perhaps an issue for bullets that go from supersonic to trans-sonic speeds while in flight but all my rifle rounds remain at either above Mach 2 or close to it though their flight to the target. Likewise for all those shooting long distances up to 1,000 yards.

Not true. Look at the turbulence leaving that back of the bullet in your picture. The shock wave continues to widen from the front, but there will be turbulence at the back. If it wasn't for that, the back would be traveling in a vacuum and there wouldn't be choices of flat base and boat tail base, etc.

 

[Gunner3456]

I've heard that boat-tail bullets are better for long distance, but flat base are better for accuracy (short range).

It seems correct since the boat-tail would have a better ballistic co-efficiency and the flat base would give more area for the rifling to contact.

Is this true?

To oversimplify, a bullet with a very pointed nose and a boat tail will give you the best ballistic coefficiency (BC,) yes. To further oversimplify, that means that the bullet will shoot flatter. To be even worse about oversimplifying, you might simply call ballistic coefficiency drag. FWIW, the higher the number for BC, the better, meaning it has less drag.

As for base shape, I've never personally come to a conclusion about that because I've read too many differing opinions on it from expert sources. My personal belief at the moment but subject to change if I see a true scientific study, is that the boat tail has less drag (better BC) and will therefore shoot flatter, but that a flat base is more stable by some minute amount. Sorry I can't really answer that for you. Experts argue it.

 

[mjbskwim]

So ,because I am a simpleton,y'all mean to say find the bullet that shoots the best out of you gun,with a given recipe?

Skydiver,I'm going to load some 75g bullets and have some 68 g already loaded.I seated the 68g to the same length as the 55g bullets with the load info from Hornady.I'll see what they do when the weather gets better.
Both my ARs have a 1-8 and seem to shoot all weights about the same so far