Interesting , Remington on one chart list 6 1/2 small rifle and 7 1/2 BR small rifle primers . On another chart list 6 1/2 and 7 1/2 both as small rifle primers no M or BR . Then Hornady list 6 1/2 as small rifle and 7 1/2 as magnum small rifle. Some will say that M and BR primers are inter changeable others say the difference is more care is used making BR primers .
Bottom line you can call Remington and ask. You can call the company who published your reloading manual.
What is true is different powders react different to different primers and a change in primer can send a load past max pressure or cause incomplete burn. Temp can cause either with certian loads which may cause a loader to think a load safe in cool weather and find it way over max in hot weather ( don't ask how I know this
) .
Do yourself a big favor and call Remington.