I have a question for you all that build your uppers instead of buy them complete. What is your preferred gas block and why. Do you use the same one or same style on different calibers. Is it steel or aluminum is it clamped pinned or screwed. What are your thoughts. I have used the A2 FSB on some builds that I planned on using carry handle sights with Its pinned by a gunsmith of course and it’s cast from steel with a good fit on the barrel. The free float ARs all receive the Geissele Super Gas Block. It’s by far my favorite I have used. It’s made out of steel it screws or pins on the barrel and it’s a snug fit on the barrel. I use the SLR jig to dimple the barrel and set the screws with lock tight.