I would start with a 2500X RBLP action, Muller 8 barrel, Rotex low profile Dymalux stock, BixNAndy trigger and Holeshot Tuner. I would then top it with a Nightforce 15x55 scope. In general, anyone assembling a gun from these components can just put it together and get about 90% out of it from the box. IF I am going all out, here is the procedure I would do.
I would get my barrel unlapped and taper lap it to about 0.0003 end to end, or just get it lapped by Paul. I slug it and push the slug both directions multiple times for various amounts checking for even taper. IF it was not, I would cast a lap and finish the job. I then cut off 1 inch from the breach, indicate it in to 0.001 on the grooves in my Haas CNC lathe and proceed to thread the shank. I would cut the tenon for a 1.051 headspace action as all of my personal guns and any spec guns I build for sale are that. I do that because I can then test, sort and tune on known platforms. I bore the chamber and cut the final lead with a micro honed Henrickson reamer. My chamber is very unique and would be hard to cut with a reamer only. I then use my proprietary finish technique on it to blend the lead. I then cut it to either 24 or 25 inches, once again I have an exact number I use, and crown it with a 11 degree face and a 45 deg edge break on the bore interface area. After that I laser engrave the required ATF information and a date code and then spin it on the belt sander. BTW, this is the procedure I use for ALL my barrels that I do.
I would then disassemble the trigger and polish the problem areas in them and then install the trigger and measure the overlap on the sear surfaces. I then cut the bottom of the cocking piece to get about 0.020 overlap. I check pinfall and then tune the indenture on the case by trimming the spring until I get a uniform 0.018 deep dent on a new unfired Eley case. IF the footprint needs work, I do it first, but I seldom have to as the wire EDM cuts them so close from the start.
I install the barrel on the action to 350 in-lbs torque using anti-seize and put it in the stock and check for motion when loosening the screws. I really want to see 0.002 or less motion there at the end of the forearm. Some people claim less then that, but it is really hard to truly measure it and I have found by test that anything under 0.005 does not seem to matter. I check tracking on the stock and don't like to see much more than 0.050 motion on the target within about 0.25 inches of recoil. IF going hog wild, I will get the stock from Randy and finish sand the tracking areas myself and get it as close to perfect as possible. In the end, I am pretty sure it does not matter though.
I fit the tuner to the barrel with about 0.001 clearance and LIGHTLY lock it on. In general, there are decent tuner spots at about 135 and 200. I try it around there and if it shoots ok, continue on.
I am currently doing some testing on some batches of barrels. I chambered 30 blanks, half at my 24 inch and half at my 25. I am going to run them through the tunnel without a tuner, with a tuner and sort and record the results. I then want to see how they tune up and how ammo sensitive they are. My goal is to get 3 barrels out of them that are better than my current ones.
I guess that is about enough for now, but to me, that is what a state of the art RFBR gun would consist of. As you may surmise, it's not just the components, but how/what is done in the assembly process.
BTW, I assemble a lot of guns for people using those parts. I install the action, trigger, barrel as described, tuner, stock etc and sell them for the price of the parts plus a little for testing it when I have them available. I leave the fine tuning up to the customer as well as tuning and ammo selection. That gets a lot of people guns that are competitive for under $4k. IF I go to all the other effort, the cost is substantially more, especially for sorted barrels. I DO NOT take on those builds right now or plan to in the future. Depending on how my barrel test goes, I may be putting out a run of 10 to 15 special guns with a custom model name, serial number, stock color configuration etc. The price will be nearly double that though.