300BLK Upper build advice? please.

[MarkCO]

A couple additional questions for you gents. Does anyone use or recommend the JP silent capture spring and lo mass bcg? Is an adjustable gas block a good idea or unnecessary? I want it to be vewy vewy quiet...

Finally, for now, is the main benefit of a machined billet upper and lower strength?

JP SCS and lo mass BCG...not much benefit in a PDW. I run low mass systems in all of my .223 ARs, but in the heavier calibers, just not much, if any benefit. Low mass will open a bit sooner and technically, it might be a bit louder. I do not run adjustable gas in mine due to the fact that I do not want to chase the tune is it changes and want 100% reliability. THis is the BCG I use in .300BOs: http://www.usamade-ar15parts.com/product-p/bcgrnb.htm

I like a barrel with a slightly undersized gas port, get everything dialed in and the last thing I do is open the gas port incrementally until I get full function, then slightly ream that out. I good clamp style gas block that does not leak, preferably made of the same material as the barrel is what I prefer.

Billet receivers are bling only.

When you look at HGs, you want to consider the connection between the barrel and suppressor. Do you want that under the HG or not. I have one set up with a 10.5" barrel and a 10" HG and another with a 15" HG so the suppressor just barely peeks out. I do like the ability to have my support hand out a bit further on the 15" HG one, but I won't shoot that one without the suppressor.