My reply is only from experience. Chambers do very, even within the Nato group. I have shot hundreds of rounds out of two of my match rifles with no issues. I understand that the Nato round is loaded to higher pressure than SAMMI, but so are my match rounds. I did start low and work my way up to get to my match loads dialed in. I have only shot the 55 gr 5.56 loads in my guns which are not R15, so I will say be safe in your Remy and only fire SAMMI loads!