re: Question about the 300 blackout..

You can either look at the adjustability of the jp spring system but they are a little bit expensive. You wouldn't be changing the spring in the stock but more likely the buffer weight. When I was building my 16inch 300 black I ended up drilling out the gas port in the barrel because that was my limiting factor in the gas system since my adjustable gas block was already maxed out and it still wouldn't cycle suns perfectly. Now most people will not have to go that far.