I'm considering an ar15 in the near future. I'm just wondering if there is any benefit of getting 5.56 vs 223 if I can find the gun in the configuration I want? I realize I can shoot 223 in a 5.56, but not the other way around. I will porbably ONLY buy 223 or reload 223 cartridges, so is there any real reason to buy a 5.56 when there are a lot of ar15's chambered specifically for 223?
Is there be any loss of accuracy in a 5.56 using 223 ammo?
My most likely usage will be varminting (pdogs) with a scoped gun.
Thanks for the info, and sorry if this has been answered before. I searched but couldn't find any posts answering this question.
My previous post did not answer your original question so I will do that in this one.
What really makes a 5.56 NATO cartridge is the use of the SS109 type bullet (62gr FMJ with 10gr steel penetrator) at 62,000PSI if memory serves. Because of the shape of the bullet, (it has a very bulbous ogive,) and the fact they pack a lot of powder in the case, there is a very realy possibility the chambered cartridge will have its bullet contacting the rifling in a tight .223 chamber, with a short leade. This type of bullet is not designed to be loaded into the lands of the barrel and so the initial pressure may climb higher than expected as the bullet tries to engrave itself into the rifling without its usual running start. If you add in the higher pressure at which the 5.56 is usually (but certainly not always) loaded, yu could get quite a pressure spike, again in a tight .223 match chamber.
But this is only using this bullet, the SS109 in the M855 ammo and that is the only 5.56 NATO loading.
The NATO chamber is also made looser than required for 2 reasons; 1- it is supposed to be able to chamber any NATO ammo made by any country that produces NATO ammo so the variations have to be taken into account. 2- The M16 with NATO chamber is a martial weapon, designed to be used in all conditions, including mud, sand, snow, rain, etc. abd as such must be able to load any NATO ammo under less than clinical conditions.
The .mil is not interested in gilt-edged accuracy out of these rifles, with this ammo; the minimum accuracy of this combination is 4MOA.
I have AR-15s with NATO chamber, Wylde chamber and 5.56 Match chamber. The last one is a product of Krieger barrels and it is a VERY tight .223 chamber with a long leade to accomodate my 80gr bullets seated out to 2.45+. I can assure you that my LR match loads are even higher pressure than the 5.56 NATO rounds, but I take other steps to tame the pressure curve. I used to swear by the Wylde chamber in the prior incarnation of this rifle's barrel, now I swear at it for the good reason that none of the brass that I used to shoot in it can function properly in this match chamber. So, I had to get new brass for this barrel and I must make sure to never use this brass in the evil Wylde or NATO chambers.
I would never use this match rifle in a situation where perfect funtion is required at all times, or even rapid fire. This is a match rifle, dedicated to one purpose only; competition.
On the other hand, I am now talking my Wylde-chambered National Match rifle hunting. It has never failed my in Service Rifle competition where rapid fire is required and it is more accurate than my NATO-chambered ones. It's does not have the high degree of accuracy that my match rifle has and requires, but Service Rifle did not require that degree of accuracy and certainly neither does hunting or even varminting.
So, what does this all mean. If you buy ammo and you insist on using M855 equivalent only or greatly; you need a NATO chamber. If you want great accuracy and reliability and the capability to shoot M855 junk at time, you need a Wylde chamber. If you handload and you need superb accuracy, you need to get a .223 match chamber and tune your loads to the rifle. You may want to make sure it can handle the bullets you want to use, if you're looking at longer ones.
FOr the purposes you have stated, I will add my vote for a Wylde or equivalent chamber. Yes, there are several different chambers that accomplish the same thing as the Wylde but the later is more prevalent.
Finally, and this is where an argument can start, I suggest you get a 1:8 twist and no faster, with your Wylde (or equivalent) chamber and get it in a stainless steel barrel.