[rzym20]

When cleaning my Rock River M4 I noticed that there appears to be a weight of some sort inside the recoil buffer I removed from the stock. When I shake the buffer end to end, this weight clearly "thunks" back and forth. Seem like this shifting mass will only add to felt recoil impulse and slow down second shots.
1) Is this weight inside the buffer normal?
2) Is it normal that this weight shifts inside the buffer?
3) Is the shifting weight somehow essential for reliable weapon function?

Thanks!