Re: F/S Rock River Arms Varmint A4 SS - NIB
The rifle is New-In-The-Box and has never had a round chambered in it so I would have to rely on USMC M38A1's experience to answer your question.
I believe that the 223 Wylde chamber has a longer throat than a standard 223 Rem chamber. It should, therefore, accomodate longer, high BC bullets. It would make sense with an 8" twist barrel.
As indicated, the rifle comes with one factory mag, the RRA Safe Case and Manual.