Hello, I am currently gathering a list of things for my AR15 build. I decided on CMMG upper in the stainless steel bull barrel. my question is what is everyone's opinions on the barrel length. I am torn between 18 and 22 inch. My primary use would be for varmint but would be a gun that i could have around for home defense as well. just curious as to what the recomendations out there are for the appropriate barrel length. thank you.