I'm afraid I don't understand the question. Sorry, but it's still early and I am only on my second Mt. Dew.
Are you talking about changing the bottom metal of the rifle itself to accept an external magazine? Or changing the bottom metal because you want too? Or changing it because you rechambered the rifle from a previous caliber?
Give us a little more to work with here brother.
Sorry, i'm workin with lingo I don't totally understand yet lol. I'm talking about changing the bottom metal of the rifle to accept an External Magazine.
more specific, now that i have more details, its a 05 or 06 winchester Model 70 .300 WSM