I’m sorry bud, I’m sleep deprived at the moment… I have a 10 day old daughter and the sleepless nights are hitting me bad!
Yes, I meant a 20” barrel. As far as shooting I want to be able to do PRS, thus I was thinking on an m-lok hand guard and attaching an arca rail to it, like the one MDT sales, that way I can use the bipods I own already.
I do have a gas gun already, Aero M4 5.56, 12” barrel , I use it for CQB style shooting up to 100yds. As far as building the AR, I’ll physically build it myself… well, I’ll put it together myself and will then take to my gunsmith just for a final checkup before hitting the range with it
Cheers!
I have a few more questions. Do you have a weight requirement? Do you have a rail length requirement?
The secret to accuracy in an AR (other than barrel and trigger selection which are the top priorities) is rigidity of the barrel to upper lockup and generally a more rigid rail. Thermal fit is ideal but can oftentimes be an issue with tolerance stacking. BCM uppers generally always require thermal fitting of the barrel extension to the upper (heating up the upper to slightly open up where the upper and barrel meet facilitating a very tight fit), although this can be done with Loctite and or shims to take up any additional volume in the meetup. When done properly I have seen the same result in regards to accuracy. At the end of the day it comes down to the barrel, and the difference between all the things I am about to say and just throwing a gun together is probably .35 MOA. There is bell curve to this and it all depends on how anal you want to get and how much money you want to spend.
The second piece to that is the how the upper reciver and the rail interface. You have three types of options:
1) a tradition barrel nut / upper receiver interface. Probably the least ideal for your use case but there have been a million amazing precion ARs built off this setup so there is an argument to not overthink it. It has far more to do with the indian than the arrow.
2) a monolithic upper receiver like LMT's or VLTOR's. The general negative to this type of system is weight and probably more important in your case, the length of the handguard as they are typically shorter than 13". But this is probably the best option if you are looking for pure precision.
3) the third is more of a hybrid approach like you see from Larue, DD, Aero, KAC ect. where the flex of the rail is be transferred to the upper reciver vs the barrel nut. They all have different ways of doing it and the systems can oftentimes be proprietary and not meant for builders, as in you would need to buy a full upper and swap parts.
Upper to lower tightness is not as important as the upper itself but looking for builders sets is helpful.
If I was in your shoes and I wanted to build it myself I would probably look at Aero on the affordable end with their M4E1 upper receivers & handguards (they sell M4E1 builders sets from time to time that for the money are the easy button). If I was looking to spend more money I would be looking at radian with their builders set, V Severn builders set if you are looking to save weight, a KAC URX4 rail along with a BCM Upper, or buying a Larue ultimate upper when they come back in stock and selling the barrel and BCG or doing the same with a DD V7 upper.
But most likely I would call up Steve at Citizen Arms and tell him I have a 20" proof barrel and let him work his magic. He will point you in the right direction as far as parts go and it will be a .5 MOA shooter. He has made made amazing guns with decent mil spec parts and ALG handguards that shoot lights out. His customer service is some of the best in the industry. I can't say enough good things about him.
I have been involved in more than a few of these types of builds so if you have specific questions - shoot.
