Is it true Remington R P brass isn't designed to be reloaded only fired once .
no, its not true.
I read a post on another forum , sorry , this person wrote , I contacted Remington and RP brass was loaded for one firing and not recommend for reloading .
That's lawyer speak for "we aren't responsible if you blow yourself up reloading our brass."
I think this is pretty much true. I think its a bit of a dodge, and going from what this guy said Remington said, ok, fine, they may not "recommend" reloaded the fired brass from their loaded ammo. But not recommending is a long way from any kind of prohibition, or even a warning.
Consider this,
"we don't recommend you reload the brass from our ammo, we recommend you buy our unfired brass for loading (it's better for our business)"
I doubt there is any significant difference between the brass they use loading ammo and the brass they bag and sell for reloaders to use. Only one ammo company I know of ever did that and that was Norma.
And, I don't know if there was any difference in Norma's brass (I rather doubt there was) only in the case marking. Norma ammo said "Norma" Brass that Norma made and sold for reloading was stamped "Norma Re"
(Re =Reloading).
The only ammo I know that is intended for single use and NOT to be reloaded is the aluminum case CCI Blazer.
Steel cased ammo is not intended to be reloaded, but it can be done (and don't use your regular dies!!!)
Berdan primed ammo is reloadable, BUT its not a practical thing to do (in the US) as the Berdan primers are not easily obtained these days. You can get the needed tools easily, but the primers are scarce...