UPDATE 10/18/13:
Rather than starting a new thread, I am updating this one to hopefully address my question. About a year ago I began actively working on a build concept that I have been bouncing around in my head for quite a while. The purpose was (and is) to build a one-size-fits all, jack-of-all-trades, all-purpose go-to rifle. This has been a journey and a learning experience so far, and my plans have changed quite a few times, but the desired end result remains the same. To build the rifle I would choose if I could only have one rifle for the rest of my life (however long or short that may be given the reasons I may be grabbing said rifle). I am not trying to build the perfect rifle for any one specific purpose, I am trying to build a rifle that will perform adequately in as many conceivable scenarios as possible.
Here are my current goals:
Accuracy: 1 MOA (measured as a 10 shot group of Mk262 Mod 1 ammo)
Barrel Life: Accuracy not to exceed 1.2 MOA for 6,000 rounds of semi-auto fire
Effective Range: 0-600 meters
Reliability: As reliable as current technology allows - this is a “bet my life” gun
Features: Suppressor ready, low recoil, good round capacity, ability to mount a light, optic, and BUIS
Weight: TBD… as light as possible while meeting the above criteria (hoping for ~8lbs unloaded, w/ optics)
Length: TBD… as short as possible while meeting the above criteria
If my choice of the AR15 platform and 5.56mm caliber has not already been assumed, I will confirm that that is my decision. I believe the 5.56 AR15 platform is the best choice to meet the above goals.
I have already built my lower. Here is the parts list and reasons for my choices:
Lower Receiver: Seekins SP15 forged lower - forged 7075, type III class II anodizing, and dimensionally in spec as far as I can tell. M2 PMAGS drop free empty (have not tried loaded). It was available when I was looking to purchase and others weren’t, and I like the machining on the front of the magwell.
LPK: White Oak Armament LPK with the addition of a Magpul Enhanced Trigger Guard, BCM Mod 1 grip, and BAD-CASS. Parts were selected due to availability, reputation, ergonomics and because I want the rifle to be at least partially ambidextrous for weak side shooting.
Trigger: Geissele SD-E. I wanted combat reliability first and foremost, but with more precision and a slightly lighter weight to better serve the shooter for longer shots (400, 500, 600 meters). According to Geissele’s website, the SD-E also has a slightly shorter reset length than the SD-C. The flat bow was chosen for enhanced trigger “feel”.
Stock: Magpul STR - chosen for a better cheekweld, storage capacity, shielded lever, moderate weight and the ability to fully collapse on a Vltor A5RE.
Receiver Extension: Vltor A5RE - chosen for use with the Vltor A5 system for recoil reduction and better performance with a variety of ammunition.
Buffer: Vltor A5H4 (will reduce to an A5H3 if necessary)
Spring: BCM rifle spring - chosen for reasons of availability
Castle Nut: BCM - chosen for reasons of availability
End Plate: Noveske QD - probably would have gone with the IWC QD end plate if it had been available when I purchased this, but I don’t regret it.
*I properly torqued and staked the receiver extension.
I have purchased some parts for my upper and but still need the major ones. Here is my list:
Upper Receiver: Vltor MUR A1 - not purchased yet. I am leaning toward this over the Noveske MUR due to price, availability, and better compatibility with free-float rails if I want to change in the future. I plan to drill the hole for the Noveske anti-rotation pin.
Rail: Noveske NSR 13.5" - purchased for minimal weight and slim profile (small hands). I plan to cut the top of the rail for compatibility with the Noveske Switchblock and mount the light and front sight ahead of the block if I have enough room, otherwise the sight will be mounted directly behind. Nothing will be mounted to the sides or bottom unless I decide to try a Grip Pod.
Charging Handle: Rainier Arms Raptor - purchased for reliability, ambidextrous ergonomics and to minimize the chance of pinching a finger. I also like the extended right side latch for easier charging when prone and supporting yourself with your left arm.
BCG: LMT Enhanced Carrier/LMT standard bolt - not purchased yet. I decided on the E-carrier to increase reliability across a broader range of ammunition, reduce recoil, and relieve gas pressure when suppressed. I am leaning toward the standard bolt at the recommendation of multiple members.
Barrel: Noveske 16" Recon barrel w/ pinned Switchblock - not purchased yet. I am heavily leaning toward this barrel to hopefully meet my goals for accuracy and barrel life. I am electing the Switchblock option to reduce recoil when suppressed, minimize added wear, and the ability to elect to use the rifle like a bolt action.
Muzzle Device: TBD… Will be chosen based on suppressor compatibility once I decide on a suppressor.
Optic: SWFA SS 1-6x24 - not purchased yet. Leaning heavily toward this option at the moment, but I sill have more research to do. I wish it were lighter…
BUIS: KAC folding 45* offset sights - not purchased yet. Chosen for the ability to quickly transition to irons without removing the scope, and the ability to deploy or fold down at will. To my knowledge they are the only folding offset sights currently available.
I’m pretty well set on all of the things I have already purchased, and feel like I have a pretty good plan in place. My only current concern is whether I should continue to wait for the Unicorn blood (Noveske barrel, LMT BCG) or buy something else and be done with it. Is the Switchblock, E-Carrier, and A5 system redundant? Am I over-compensating for suppressor use? I understand that I can run a suppressor just fine without any of these parts, but I do believe based on my research that each part improves reliability and function with a suppressor. The question is, at what point (if any) does it become redundant? Meaning, will I see no appreciable benefit to employing all three parts vs only employing two, or one? Or will I still benefit from each one, even if on a miniscule level?
Thanks for sticking with this long post. If you have any questions comments, or suggestions please share. Original post below.
PREVIOUS POST:
Hi everyone. I’d like to start my first AR build, but I’m looking for some outside opinions first. Feel free to comment on my parts list and critique any of my reasons for choosing a certain part. I’m not really looking for pats on the back here, or “nice job, looks good” (although if that’s what you think I do appreciate it), I’m more looking to make sure the completed rifle will meet the purposes it’s being built for.
So, onto the purpose of this rifle. Straight to the point, I want to build a combat rifle. 90% of this rifle’s intended purpose will be as an all purpose, well rounded assault rifle that could be relied upon should the SHTF, civil war, WW3, whatever your personal beliefs are (I personally don’t put my money on a zombie apocalypse, but to each their own). The remaining 10% of it’s purpose will be as a target/training rifle to maintain my skills. Four key features I’m looking for, in order, are reliability, durability, accuracy, and quick handling (referring to a combination of weight, recoil management, and target acquisition). Now before you flame me, yes, I realize that there is a very good chance this rifle will never be used for its intended purpose, and if that’s the case I am glad. However, I’d rather have and not need in this instance, than need and not have, regardless of how small the chance of needing is.
Goals:
[ul]100% reliability (not realistic I know, but I want to get as close as possible.)[/ul]
[ul]Repeatable 1.5MOA accuracy or better[/ul]
[ul]Effective range of 0-400 meters or more[/ul]
[ul]7.5 lbs or less unloaded with optics (thinking my proposed optics will push me over that weight… 
)[/ul]
[ul]Suppressor ready[/ul]
[ul]Ability to maintain accuracy and reliability to a high round count before needing to replace parts (high meaning in the realm of what the best components on the market are currently capable of)[/ul]
[ul]Ability to handle a high volume of semi-auto fire in a short period of time without damage, if necessary[/ul]
Parts List:
Lower Receiver - Forged 7075 with a flared magazine well. Looking at either a Spikes Tactical or the Rainier Arms zombie edition, just to be different. 
Does anyone have any experience with the receiver tensioning screw on the Ranier Arms lowers? If they work I’d prefer that over using the buffer wedges that are easy to lose and usually make the receivers too tight…
Lower Parts Kit - I’m told Daniels Defense makes the best, but they’re always out of stock. Also heard CMT/Stag and Rock River are good, and a little less spendy. What are your thoughts? I’d also be interested in a good kit minus the grip and trigger assembly, if there is such a thing. I’m not a fan of the basic grip or a gritty trigger… though I’ve never shot a DD, CMT/Stag, or RR trigger. I have heard excellent things about Geissele triggers.
Stock Kit - Magpul CTR Mil-Spec Stock Kit from Rainier Arms. $130, includes 7075 forged buffer tube, spring (which I will swap out for a Sprinco), H buffer, castle nut and endplate.
Upper Receiver - Armalite SPR Mod 1 Midlength. I’m pretty much sold on this one. Forged 7075, forward assist, dust cover, monolithic rail, interchangeable sides and bottom sections, includes barrel nut… what more could I want? Expensive and usually out of stock, but worth it I think.
Charging Handle - PRI Gas Buster Charging Handle with Combat Latch. Planning on doing the silicone mod as well.
Bolt Carrier Group - I would prefer a full auto BCG, just seems more reliable to me. The three big names I always here as “the best” BCGs are Colt, BCM, and LMT. LMT’s have a MIM gas key, which if I understand correctly cannot be properly staked without cracking? I also think they are semi-auto only, right? So its down to BCM or Colt, BCM having the advantage on price and Colt on overall quality, from what I’ve read on here. Flip a coin?
Barrel - 16" Noveske N4 Light Recce with pinned Switchblock. This seems to be the best match for my accuracy and durability goals that I have found, as well as being suppressor ready. Settled on a 16" after not being able to find a pinned 14.5" with the pinned Switchblock available without buying the complete upper from Noveske. 16 inches should give me a little more energy & velocity anyway (a little less than half the difference between a 14.5" and a 20" IIRC?) and hopefully the extra inch and a half wont be that noticeable in weight or maneuverability. I’m not opposed to doing an SBR, I just don’t think its the best choice for my goals. Feel free to persuade me if you think otherwise.
Flash Hider - AAC Blackout 51T Flash Hider. Enough said.
Sights - I’ve used metal back up sights before and liked them, but I’m sorta eyeing up the Magpul back up sights. Has anyone used them? I’m a little concerned about their strength/durability being plastic, but they are cheaper and probably lighter than iron sights. Either way, I want to swap out the front sight post for a fiber optic post. Are the Magpuls changeable?
Optics - Eotech 512 and a 3x magnifier on a flip-to-side mount. Do I need to use the Eotech magnifier or will other magnifiers/mounts line up? I think it’s highway robbery what Eotech charges for their products… but I guess you can do that when no one else makes one. Reasons for settling on the 512 are: Parallax free, 65moa ring allows for rough distance estimation, AA batteries are easier to come by than CR123s and AA Lithiums last just as long. I thought about the 517, but I think I would prefer the buttons on the back rather than the side?
Dedicated 22LR Upper - Last but certainly not least, a CMMG 16" 22LR upper for more shooting for less coin without wearing out the good stuff. Cheap sights and/or a red dot/reflex sight of some sort to keep it similar to real set up.
So there you have it. I’m trying to keep the rifle simple and functional. I don’t see the extra weight of grips, lights, lasers, etc… offset by the benefits (if any) they provide. Please let me know what you think, what you question, and what you’d do differently and why. While i do have a budget like anyone else, I’m trying to push it as much as needed/possible. I don’t want to look back and think, “man, I should’ve spend the extra $$ and just gotten that.” I’m also not entirely stuck on the AR-15 platform or the 5.56 cartridge for that matter. I settled on both for price, availability, and the fact that they are common and plentiful. And should the SHTF and I need a rifle, I don’t want to have to scrounge for 6.5 Grendel rounds or parts for a European bull pup if something breaks. If you have a different suggestion, let me know. 
