You will need MPN: SAKB0200 for .300 Blackout.
The .30 Cal model will very likely work, but I would highly recommend contacting Spike's directly to verify that the bore diameter of the .30 cal model will accommodate the diameter of a 7.62x39.
The Spikes Tactical Barking Spider2 Krinkov Muzzle Brake does not include a crush washer; however, a crush washer isn't necessary for installation.
The Spikes Tactical Barking Spider2 Krinkov Muzzle Brakes do not include a crush washer. So one will need to be purchased separately.
Spikes Tactical does not state if the OAL of 3.75" includes the threads. I recommend contacting Spikes Tactical for that information.
The CZ Scorpion Evo 3 S1 has a barrel threaded for 1/2x28. So the 9mm model of the Spikes Tactical Barking Spider2 Krinkov Muzzle Brakes will work with that gun.
The internal diameter will vary based on the model of Spikes Tactical Barking Spider2 Krinkov Muzzle Brake you are talking about. However, I recommend contacting Spike's Tactical for that information.
The Spikes Tactical Barking Spider2 Krinkov Muzzle Brakes will work with a Smith and Wesson M&P15 Sport. You will need a 5.56x45 model and make sure the rifle is threaded for 1/2x28 to match the Spikes Tactical Barking Spider2 Krinkov Muzzle Brake.
The Spikes Tactical Barking Spider2 Krinkov Muzzle Brake can be used on an AR15. If you AR15 is chambered in 5.56/.223 and has a threaded barrel with threads that are 1/2x28 TPI, then model number SAKB0100 will work with your rifle.
The manufacturer doesn't specify the threading of the Spikes Tactical Barking Spider2 Krinkov Muzzle Brakes endcap. I recommend contacting the manufacturer in regards to that information.