I have read on other forums that some have had difficulty firing military surplus 7.62 out of their R-25. Needing two hits on the harder berdan primers. One fellow said that Remington purposely had them built this way, and that he is selling his R-25 and waiting for a DPMS.
I just got off the phone with DPMS (manufacture of the R-25, Bushmaster makes the R-15, .223). They said there is no difference in firing pins or bolt between the R-25 and the DPMS. In fact he said the upper, lower, and barrel as well are indentical. He also stated that they are happy to service the R-25 just as their own. DPMS and Remington do not recommend foreign military surplus ammo for their rifles.