5.56 x45 vs. .223 accuracy?

[JimBobKelley]

Ok being new to my AR-15 I have lots of questions and here is my latest one. I went to the range today to sight in my new optics took some Hornady 55gr. v-max in .223, Hornady 55gr. SP Brass training in .223, Federal FMJ 55gr. in .223 and I picked up a case of Federal 5.56X45 62gr. with green tips. I sighted in at 100 yds with what I thought was the most accurate ammo I had the Hornady v-max and accuracy was .75 to 1.5 MOA with 3 shot groups when everything was held as it should be resting on sand bags. I did have some flyers but I assumed it was just me not doing my part.

I then tried the 5.56 ammo out. I started at 200 yds, just for some fun, and first noticed the increased recoil and muzzle flash, I do not have a flash hider on my AR just yet. I shot a hole in the target which measured roughly 2" by 2". My AR is a Bushmaster with 5.56 stamped on the barrel and .223/5.56 stamped on the lower so I know the head spacing is just right for the 5.56 round but was not expecting it to be too accurate with the 5.56 ammo.

I guess what I am getting at is I thought with a 1 in 9 twist the 55gr .223 round was going to be more accurate than the 5.56. I had less flyers with the 5.56 than .223. I shot 60 rounds and I only counted 4 that were outside the 2x2 hole and they were only .5" and .75" away. Since my rifle is chambered for 5.56 would this make this round more accurate than .223? If so why, is it the spacing difference in the two cartridges?

 

[Dawico]

5.56 chambers are a tad longer than .223 chambers (as is the ammo). That is essentially why you can shoot .223 out of a 5.56 chamber but not vise-versa. There is more to it than that really, but that is the basics. .223 ammo has some freebore before it hits the rifling, so that can be why the 5.56 ammo is more consistant.

Some ammo just shoots better also. Guns and ammo can be quirky like that.

 

[JimBobKelley]

I guess maybe I just found it's "sweet spot" so to say. Ammo was rather inexpensive also but I could do without having them on stripper clips. Taking them off slowed me down.

 

[JimBobKelley]

If the free bore space is there you are talking about the distance the round is from the lands, correct? Does this mean that the 5.56 is touching the lands and is that a problem? I don't want to put too much pressure/wear and tear on the rifle than needed.

 

[Davetex]

Here is a good stripper clip video:
How to use a 5.56 stripper clip with USGI and PMAG Magazines - YouTube

 

[Texas42]

Your rifle is either a .223 remington or a 5.56nato. While they are very similar, they are not identical. The 5.56 nato is designed as a military round, and made to be more reliable than accurate. The more accurate guns are generally chambered in .223 and have tighter tollerances. The fact that your rifle might like one ammo more than others is expected and common. If your gun is a .223 remmington, you should not fire 5.56 nato through it.

Ammunition is not made equal. cheap ammo tends to have less precision in the amound of powder, OAL, weight of the bullet ect. You can get ammo with more consistent loadings and better bullets, but it costs more. Depends what you want to do. The right bullet for the right job.


FYI, 3 shot groups are a terrible way to assess the accuracy of a rifle. 5 or 10 is a much better method.

 

[Dawico]

If the free bore space is there you are talking about the distance the round is from the lands, correct? Does this mean that the 5.56 is touching the lands and is that a problem? I don't want to put too much pressure/wear and tear on the rifle than needed.

Yes, freebore is the distance from the bullet to the lands before firing. The 5.56 isn't touching the lands and will be fine in a 5.56 chamber. It could be a problem firing 5.56 ammo in a .223 bore. This is also complicated by 5.56 ammo being loaded hotter than .223 ammo, hence the extra flash and recoil that you noticed.

 

[Texas1911]

Run some Federal Gold Medal Match, Blackhills Match, or Hornady Match in a 69 grain bullet through your gun if you want to see it's accuracy. All the ammo you listed is 1 MOA at best through a good gun.

ARs in general will shoot about 1 MOA on average with good ammo. There are some that will do sub-MOA consistently. By consistently I mean 5 - 10 round group after group. By comparison a great bolt action will hold around 1/2 MOA all day ... so the 1 MOA is nothing to sneeze at.

 

[JimBobKelley]

Thanks for all the help. I will try some heavier ammo to see what I can get out of the rifle.