[JimO]

From what I understand the 5.56mm nato round is the same size as .223, but 5.56 is heavier, hotter, and higher velocity military round. and the .223 is the civilian version of the same round.
According to Bushmaster literature "If you own rifles specifically chambered for the .223 Remington, you should not use the 5.56mm ammunition in them as it is considered to be an unsafe ammunition combination."
My Ranch rifle says:
Ruger
Ranch Rifle
Cal..223
I have no real need to shoot anything but .223 right now, but if
I come across any 5.56 ammo do I buy?
Is it safe to shoot 5.56mm?
Also, I assume the AC556 is named for 5.56 ammo.
Any comments?

 

[Bear 1769]

Jimo, the mini 14 uses the military A2 chambering, it is safe to use the.223 and the 5.56 in this rifle. Look at page 8 in the owners manual.

 

[lcm]

JimO,
Bear is 100% correct. If you don't have a manual check out
http://www.ruger.com/Firearms/SE-InstructM...tManualsRI.html
and click on Mini-14 ranch, scroll to pg12