.223 Full Metal Jacket Boat-Tail?

[xx AG xx]

What would be the difference between standard .223 cartridge and .223 Boat-Tail cartridge?

I don't know anything about this type of ammo, hence the question.



AG

[Orion0317]

The bullet on the left is a standard round, the other three are boat-tails. Now, those are NOT 5.56x45 (.223) they are 6mm, but they show the difference fairly well. Boat tail rounds are generally used as match rounds due to their increased areodynamic properties.

[JCWohlschlag]

Bullets can either have a flat base, like the one on the left (#1), or can have a tapered “boat tail” base, like bullets #2, #6, and #7. Boat tail bullets are designed to have better aerodynamics by having a smaller drag coefficient.

Addendum: Great, now even the damn n00bs are beating me to the post. (Just kidding )

[d4xycrq]

Boat-tails are my choice when reloading! Makes 'em easier to seat in the case mouth. According to the reloading manuals, though, they are not always the most accurate choice.

Ray

[Rundownfid]

FMJ bullets generally have an exposed lead base and the tip is solid metal. This is somewhat problematic from an accuracy point of view as it is the tail that steers the bullet. I know that is counter intuitive, but so, if you want accurate ammo ensure the bases are uniform and undamaged, tips can be a bit battered.
Boat Tailed Hollow Points, on the other hand, generally have a jacketed base and a hollow tip, through which the lead core was inserted before being swaged down into an aerodynamic shape. Therefore the jackets on HPs are continuous where the steering takes place and thus they tend to be more accurate. Also, they have a hollow point and may expand on impact.
Were it not for international conventions there would be no place for FMJ in my opinion. Given the laws of supply and demand they FMJ can be rather inexpensive as they are made in huge quantities for the military and over-runs, etc, bring them onto the civilian market at a pretty good price.

[Orion0317]

Addendum: Great, now even the damn n00bs are beating me to the post. (Just kidding )

Hehe. Gotta keep you guys on your toes!

[Tomcat088]

Lots of good information has been presented here, although a little bit of misinformation has been presented. The info about the difference between FMJ's and boat tails is correct. The main reason for this difference has to do with the way that they're constructed, as Rundownfid presented.

Flat based bullets are sometimes more accurate than boat tail hollowpoints. Some of the guys that shoot shorter distances actually prefer them. It doesn't have to do with the "tail" steering the bullet though, it has to do with the way the back of the bullet seals with the bore, and the resulting pressure curve. Quite a bit of gas vents around the rear of a boat tail hollow point, and the gas that is surrounding the bullet can sometimes cause a bit of turbulence as the bullet exits the muzzle. Since BC doesn't play as large of a role at shorter distances, the guys shooting 300 yards or less don't care if it has a bit more drop, as long as it shoots the smallest group. For this reason, lots of 300 yard or less BR guys prefer flat base bullets for some applications.

As I said before, it is NOT the rear of the bullet that "steers" it anywhere. A bullet is set on a trajectory, and it is gyroscopically stabilized, it remains on the past it's been set on. There are quite a few other factors that effect accuracy, BESIDES the shape of the rear of the bullet. One of the main reasons that FMJ's aren't always as accurate as hollow points is related to their construction, particularly with core and jacket consistency and thickness. Because of the way they are made, FMJ's do NOT have as good of consistency in the jacket thickness, this means that as the bullet is spinning, it's center of gravity is sometimes slightly off center. Since the center of gravity is slightly off, it makes the bullet wobble just a little bit, obviously when a bullet is wobbling, it isn't going to go through a hole that is exactly the diameter of the bullet. The wobble itself makes the bullet fly not quite "true", just like a football that is thrown wobbling. Since this deviation happens differently from bullet to bullet, you can't get good consistency and shoot small groups. Another factor that influences how bullets fly has to do with their and the pressures that surround the bullet when it flies. You will almost always see subsonic bullets as "flat base". It's not just a boat tail that effects how a bullet flies at supersonic speeds, but also the angle, length, etc of the boat tail. This is why some bullets are better suited for different velocities than others. A consistent base of a bullet is necessary for accuracy, but it's more related to the pressure seal that it creates with the bore, and also the consistency means that the bullet doesn't wobble. It's all quite complicated, and I've barely scratched the surface here, but I think it's enough to say that the rear doesn't "steer" the bullet.

Now in regards to the tip of the bullet not being that important for accuracy, this is QUITE INCORRECT. Maybe at shorter ranges it doesn't make as big of a difference, but it DOES make a pronounced difference on the flight of the bullet, particularly when we're talking long range. This is part of the reason that we have polycarbonate tips on ballistic tip bullets, because it makes for more uniform bullets. There's a reason that meplat trimming and uniforming tools exist, because it makes a difference. At 500 yards, you won't really see very measurable gains, but when you talk about 600 yards and beyond, you WILL see a difference. The meplat is the place where the supersonic shockwave originates while the bullet is in flight, inconsistencies with it, WILL effect how the bullet flies and the pressures as they surround the bullet. If the pressures are sporadic, it will keep the bullet from flying as true. So for some purposes, the tip of the bullet may not appear to be that important, but to say that they don't really matter in terms of accuracy, is incorrect.

[xx AG xx]

Awesome info guys, thanks.


So I can use this round in an AR and be fine with it, correct?

I am trying to get some good pricing on a few hundred rounds of 5.56/.223 ammo and I came across this boat tail stuff for a decent price and just want to make sure I can shoot it through my AR (when I get it) and the AR wont blow up or anything else like that.


AG

[Orion0317]

Awesome info guys, thanks.


So I can use this round in an AR and be fine with it, correct?

I am trying to get some good pricing on a few hundred rounds of 5.56/.223 ammo and I came across this boat tail stuff for a decent price and just want to make sure I can shoot it through my AR (when I get it) and the AR wont blow up or anything else like that.


AG

Yes, you can absolutely use this in an AR! In fact, the current loading used in the MK 12 SPR (Special Purpose Rifle) is a 77 grain Sierra Match King OTM BT (Open Tip Match Boat Tail) round. Just make sure that your twist rate will fully stabalize the heavier round.

Fire away!

[xx AG xx]

Yes, you can absolutely use this in an AR! In fact, the current loading used in the MK 12 SPR (Special Purpose Rifle) is a 77 grain Sierra Match King OTM BT (Open Tip Match Boat Tail) round. Just make sure that your twist rate will fully stabalize the heavier round.

Fire away!

Thanks.


What ever AR i get will have a 1:7 twist and from what I have been reading and the way I am understanding this is that the 1:7 twist should handle the heavier grain bullets better.

Is this correct?

AG