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How do you know which it is chambered in?
From a manufactures point of veiw it would be safest to ream everything to 5.56 lead no matter what is stamped on the barrel.

Sent from my SM-G800Y...

If you had read the link you would realise that it is fine to fire 223 in 5.56 so perfectly acceptable to sell and market 223ammo as suitable for both and mark a 5.56 chamber as 5.56 and 223 but not...