Looking like I might have a .223 to try out. This should be fun. Hopefully my 2nd suppressor is out of jail too. If it works as advertised I might start building one of those ultralight ultralight ARs.
Let me give my opinion on this. I have built a bunvh of ARs over the years but am no expert at all. EVERY problem I personally have had has been as i deviate away "mil spec" parts. Not tru mil spec but lets say "quality standard" AR15 parts. Also using "non standard" parts makes it harder to repair, replace and update in the future. All of the malfunctions i have ever had have been when i messed with spring rates, buffers, magazines or BCG. Now I tend to stick with quality "standard" AR parts if possible. Obviously on my Grendel or other calibers some of that isnt possible and i will tune it with buffers or gas systems. But with 5.56 just stick with QUALITY standard parts.
Also you spend a LOT of money and get non standard parts trying to save 1oz on parts like recivers, buffer tubes, BCG and those things.
All that being said. Parts like stock and grip, find ergos you like and be consious of weight. Stocks alone can range in weight be 5oz. Hand guards have ahuge range of weight. If you are not using NV or aiming devices on your rail a nice light carbon rail will make a huge difference in a are that will really be felt. Even a simple BCM rail is relatively light, cheap and pretty good quality. Barrel weight is another thing. I really like the Gunner profile barrels for how they handle. Trimming weight off the muzzel end is the most important to me.
But you also mentioned suppressors. I switched feom a AAC SDN6 at 20+ oz to a Nomad Ti at 12oz. Absolutely night and day difference. All that weight removed right off the muzzel. So pick the right suppressor for the job. The light barrels handle nice and hunting shouldnt heat up the barrel with just a few shots. But the ultra thin barrels do give me more POI shift. For me it is repeatable and i always run supressed. So no big deal. But my last build i went a little heavier to decrease POI shift. But barrel weight and profile is extremely important in how the rifle will handle.
Also look at weight on scopes and mounts. I really like Larue mounts but they are almost 8oz. I also used a Aero mount which is 3.5oz. Thats 4.5 oz right there. The aero worked well but i didnt have confidence in it and switched to a DD mount at 5.5oz. The DD, Nightforce and Reptila are all around 5.5oz. Thats about 3oz lighter than a lot of mounts. Optics are also a big weight factor. Choose carefully and they will completely change the way the rifle handles.
My point is that i would skip the lightweight go fast parts on the internals critical parts. You can still build a very reasonably light weight rifle by avoiding needlessly heavy parts. For example i love the Geissele rails. But dont have any becouse i dont want that weight that far forward on my rifles. Now if i was running IR aiming devices where rigidity was key it might be worth it for me. Or on one of my SBRs the weight difference on a 9" rail is not as big. But a 13" quadrail or Geissele is a LOT heavier than a 13" carbon fiber rail or even a BCM rail.
Its all a compromise. I built my Grendel to be light. Used a Gunnar profile barrel a cheap used Odin Works rail that weighs nothing, aero mount (originaly) and a VX5HD 2-10 at 18oz. Handled like a dream. Next build in 5.56 I used a light weight match barrel that was still "light" but about 4oz heavier, DD scope mount, and a Centurion CMR rail (bomber but still only 10oz). I wanted a little more durability and accuracy/less POI shift. Still a handi rifle but the small amount of weight difference is noticable.