Buffer1 は符号付き整数ですから、Buffer1 が負の値だったときに
Buffer1>>24 は処理系依存になります。だから、
(unsigned int)Buffer1>>24
とすべきです。

[#5] The result of E1 >> E2 is E1 right-shifted E2 bit
positions. If E1 has an unsigned type or if E1 has a signed
type and a nonnegative value, the value of the result is the
integral part of the quotient of E1 divided by the quantity,
2 raised to the power E2. If E1 has a signed type and a
negative value, the resulting value is implementation-
defined.