I have an “older” 1980’s mini 14 marked cal .223. Can this be used safely with 5.56?
They are not the same cartridge. Period. The 5.56 has slightly different dimensions for chamber length /leade and uses heavier brass and is loaded to a higher pressure. It amazes me how the arm chair ballistics experts know more than the Engineers, Ballisticians, and Scientist that developed these rounds! The .223 can be fired safely in a 5.56 but the 5.56 is NOT designed to be fired in a .223. It is what it is. IMHO5.56 NATO
View attachment 13487
View attachment 13488
Both diagrams above created by Francis Flinch. You can see above, the only difference is the radiused shoulder-to-neck transition for the 223 Remington cartridge (sharp for 5.56 NATO). This difference does not affect function in any of the common 223-variant chamberings including 5.56 NATO. The case capacity is also slightly different:
" A gun guy on the radio said the COAL of the 5.56 is longer than that of the .223. The case dimensions of both are the same but the bullet is seated farther out with the 5.56 and therefore requires a longer free bore ahead of the rifling than is needed for the .223. So chambering a 5.56 in a .223 only chamber could force the bullet of the 5.56 cartridge into the rifling of the .223 chamber and cause excessive pressure upon firing.
Says a guy on the radio.
He also said people fire 5.56 in .223 only chambers all the time and it seems to work so.... "
EDIT: So much for what "a guy on the radio said". ☝ . Lol
If the chamber is such, that it is designed for both, then it is fine. Usually the chamber is a bit ovesized in order to allow the 5.56 round to be fired. In a std .223 chamber, especially anything made for target shooting, the chambers are "tight" and it is not acceptable. I have a CZ 527 Carbine in .223, and the Chamber is done based on European CIP stds which allows both 5.56 & .223. to be fired through it.Whether .223 and 5.56 are the same "Cartridge" is irrelevant to the Mini-14. From Page 11 of the Mini-14 Owner's Manual linked above:
"The RUGER® MINI-14® RIFLES are chambered for the .223 Remington (5.56mm) cartridge. The Mini-14 Rifle is designed to use either standardized U.S. military, or factory loaded sporting .223 (5.56mm) cartridges manufactured in accordance with U.S. industry practice. See “Ammunition Notice” & “Ammunition Warning”, below."
AFAIK, the exceptions to the above are the Mini-14 Target model, which specifies .223 ammo, and those rare Mini-14s chambered in .222 caliber. AFAIK, those Minis have their correct ammo imprinted on them, so a mistake is on the user.
A quick search resulted in the cartridge case dimensions I posted. It was the first source I found and I stopped searching there. I included the link where the diagram and story can be found.The 5.56 has slightly different dimensions for chamber length /leade
I view of your amazement, do you have knowledge that the story I quoted is incorrect and that the author is nothing more than an arm chair ballistics expert ?It amazes me how the arm chair ballistics experts know more than the Engineers, Ballisticians, and Scientist.
It amazes me how the arm chair ballistics experts know more .........
And there are just two examples of why this forum will never make a come-back. The quality of the members now active here.O.k. Mr. Anal. ............