I had the opposite problem when shooting the Hornady in my Rock River AR. I found it was sub 2", but the PMC shot better, followed by the Federal. The real surprise was the Wolf steel case ammo, which shoots the best groups around 1". They also shoot best in my Rock River LAR PDS pistol. I don't shoot them much, but I use them to sight my weapons in cause they work good. I don't shoot expensive AR ammo, except for hunting rounds, which is why I bought the Hornady to hunt Javelina. I am not worried in the least that I wouldn't make a clean kill on any shot, just happens that it wasn't as accurate as I expected in my weapon.

Out!

 

The standard for military 5.56 ammo is a 50 mm radius at 100 meters. So your 3 inch groups were well inside that spec.

 

As far as LC ammo goes, if I had to make a product, in an american factory, to american standards, that will ship all over the world, and all these guns from different countries, will load, and fire, first time every time, under all conditions. And not jam or flash. I'm surprised they work at all! I have three different brands of +O, and they are about 2" separation. I just remember to shoot one kind till it's gone.

 

Correction



For each instance of "American" replace with "NATO". All these will have the circle/cross. Can't do it on keyboard. The rest is fine.

 

Midwest Rookie, I think mattbfarmer is simply asking if the higher chamber pressure that results from shooing 5.56mm ammo vs. shooting .223 ammo out of a barrel chambered for 5.56mm would have any affect on accuracy. I can't answer that question conclusively but I'd expect the dominant affect is the quality of the ammo. As you noted, one would naturally expect better accuracy out of premium ammo vs. military grade ball ammo.

 

randmplumbingllc, Greenhill's formula simply predicts what twist rate is required to stabilize a projectile of a given L/D ratio. It won't tell you what twist rate is best or predict what projectile will perform best as a given twist rate. It will indicated theoretically what combinations are bad - meaning the projectile is not properly stabilized in flight. An unstabilized projectile yaws in flight and thus has exceedingly poor accuracy.

 

True.

There are many variables that affect accuracy.

Was just pointing out one.

 

You have learned what everyone who shoots a lot or reloads has learned. Better quality projectiles will shoot smaller groups. While the old wives tale that 1/7 twist barrels won't shoot bullets lighter than 60 grains accurately, is just that, an old wives tale. My Colt HBAR A2 shot 52 grain Sierra HPBT Match bullets fine. There was an article in the American Rifleman 20-25 years ago by C.E. Harris on the subject of fast twist barrels and lighter bullets. The conclusion was that cheap bullets were more likely to have flaws that increased group sizes when fired in fast twist barrels. I know of no one who seriously competes in NRA Highpower with the cheap bulk bullets, (i.e. 55 gr FMJs) even at the short ranges. In Highpower, If your AR won't shoot 1" 10 shoot groups at 100 yards, you need to find another load or another rifle. My Compass Lake tweaked Colt had no problem meeting this standard with handloads.

Bill

 

An LMT wouldn't come with a .223 barrel.

And this is like saying Asym is better than WWB. Duh - :dope:

How anyone could be surprised that Hornady .223 shot better than mil spec 5.56 is beyond me..

 

I am not familliar with the LMT, that is why I said to be sure.

 

There is an actual mathmatical formula to figure out the best bullet to use.

Google "Greenhill formula" . There is a site that you imput info and it tells you what length of bullet is best for the twist of your firearm.

Below is a link to get you started.

http://en.wikipedia.org/wiki/Alfred_George_Greenhill

Also, as stated earlier, make sure your barrel is a 5.56 barrel and not just a .223 barrel.

 

The Hornady V-max bullet is a premium bullet whereas the projectiles used in the LC, the Federal XM193 and Winchester XM193 ammo are simply a generic military style ball projectile. Premium projectiles are more uniform in terms of both balance (about the axis of rotation) and weight variation (round to round). You get better performance from premium ammo - the "cost" is a higher purchase price.

 

Wouldn't the quality of the bullet be the reason?

Hornady bullets are far superior to those in ball ammo

 

Wouldn't the quality of the bullet be the reason?
Hornady bullets are far superior to those in ball ammo

Yes, that would certainly seem to hold true.
Along with the powder, powder charge, and case.
One is made for varmint accuracy, the other made for combat & training.
Why wouldn't the former be more accurate than the latter?


But it's so fun to overthink the issue, then postulate a thousand
different theories to explain why the overthinking is justified.
What fun would there be if we were simply right all the time?

:biglaugh:

 

The only conclusion that can be made here is that your gun, in your hands, shoots better with the Hornady. Or at least on that day.

Nothing to do with pressure or imbalance. It's normal for a gun to "prefer" one round over another, sometimes by very big margins. Trick is to find the one. Looks like you're close. With 1" groups out of a 16" barrel, quit while you're ahead and stock up on those Hornadys.

 

Moxie hit the nail on the head.



I see it the exact same way.

 

I believe the NATO specification has a broader tolerance on pressure (powder) than SAAMI.

The ballistic coefficient of the XM193 is roughly .243 and the V-Max is roughly .255. If memory serves correct, a higher ballistic coefficient means better (flatter) trajectory.