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"If sense is so common ..... why is it in such short supply?"
No, because if you milled into a regular 858 from the outside the mill would break into nothing. The CZ 958 was designed so it would be impossible to machine from the inside of the receiver to accept FA trigger parts by having these "scaloped" cuts next to the trigger pivot on the outside of the receiver.
You make valid points but my first consideration is "speed" and "cost" of production. There will be room for some entrepreneurs to manufacture railed gas blocks etc. if I try to make the design be everything for everyone we will just incur further delays and increase production costs. I think the two basic models will meet the requirements of the majority.
No apology required. This is a tough industry as we are completely unorganised with no clear leadership or direction and often we work in opposing directions to each other, which causes time consuming processes to take longer than they should. All to often Government Policies are accepted as law.
Someone message me once there available to purchase. Forget all the worrying about frt. when it's here, it's here.
If it is the standard gas block I am sure NEA can rejuvenate their railed gas block and change the height to match the receiver rail if there is enough demand. I would just kindly ask that you deal with the muzzle device issue without having a pin to secure it. That should be a relatively cheap fix. Also, would like to know if you will have a preorder system.