CB, I think you are referring to something like
this.
Also, I agree with your guys' vote for the velcro-based systems.
- they seem to have more positive hold on the cartridges (preventing them from falling out due to recoil, even when cartridges are placed with primer facing down).
- they are swappable -- facilitating efficient reloading
- they can be placed pretty much anywhere on the stock and receiver (and removed from the stock for shooting left-handed; the permanent screwed plastic holders punches one in the cheeckbone during recoil when shooting from support side).
- velcro-based systems cost less (sometimes much less) than plastic ones. so if one wears out, it can be replaced easily.
- no need to alter factory system for holding trigger group in place and rely on aftermarket screws to attach plastic holders to the receiver
Now that I think of it, I frankly cannot see any downsides to using velcro based systems. Can anyone point out any significant downsides?