Words of wisdom Surf.   

{a little snipping going on...}

- I also don't suggest buying the 6940.  Being free floated, they are the most accurate in the 6xxx class of the Colt rifles.  However as others have mentioned it is a monolithic rail and non traditional barrel nut assembly, so your options for future modification is greatly limited.  If you pick up a say a 69xx or 67xx free floating it will improve accuracy performance and will leave far greater options for configurations as experience grows.  Colt rifles and their barrels are pretty darn accurate.  If you don't mind weight or have a bench rifle the HBAR or Heavy Colt barrel is extremely accurate.

The only thing I'd add about the 6940 is, I never intended to try and improve on the basic components,  If you see yourself swapping out barrels, it's not that easy even with the proper barrel nut wrench and barrel extension tool.  For one-time use, it's cheaper to have a gunsmith do the repair than buy the tools!  There are just too many good things about the quality of the 6940 to let two parts be a deciding factor.  But, as I said earlier, going back in time with today's options, the Colt OEM2 would be my pick over the 6940.     

- Headspace should not be a big concern when building this rifle if we are choosing quality parts from good manufacturers and buying a complete barrel assembly (barrel and extension).  Headspace is set from the barrel manufacturer between the barrel and extension itself.  You can confirm headspace via simple go or no go field gauges if you feel the need.  Now if you are doing a stripped barrel and separate extension, that is different but almost no one does this, it doesn't make much sense for 99.9% of shooters.

I built a Spike's Tactical rifle using a striped upper and lower.  The barrel was from BCM with (supposedly) good quality control.  Didn't bother with head space gauges, and it shoots great.  If you get quality barrels and uppers, the head spacing is going to take care of itself, just as you said.  It's a critical detail to make sure if you use cheaper brands or blems, you should maybe have a gun shop or friend with the proper gauges do a 2 minute check.

I recently had a guy from the DoD in one of my courses.  He had an "assembled" M4 (personal weapon) done by a guy "at work".  It ran great for about 500-700 rounds of hard use, but kept crapping out as time went on.  Yep, castle nut backed out, rail came loose, barrel was not torqued properly (probably torqued and then backed off or not torqued to proper spec), trigger took a dump and safety started free spinning.  Yes this guy "at work" had also "assembled" several rifles for those within LE and the military and I am going over many of them as I get the time.  This is not singular example but a common problem that I see often.

Getting the proper tools and learning to use them correctly is a big deal in any hobby.  Lots of people are wanting to swap an A2 handguard/sight setup for a free-floated, low profile gas block and free floated hand guard of their liking.  I've seen YouTube videos of young men telling you to cut the A-frame sight off the existing gas block to avoid having to pay for a low profile version -- WHILE IT'S STILL ON THE BARREL!  That's after they have you also cut the delta ring to avoid removing the barrel.  When you try to do things cheap, they can wind up costing more to fix than doing it right the first time.  And you'll then have the tools and knowledge to do another rifle, and another.  If I remember correctly, the torque range is pretty wide for the barrel nut on a standard AR, to allow alignment of the gas tube through the notches in the barrel nut.  I used a torque wrench to make sure I had at least the minimum torque.  I also used quality barrel grease.

It takes time and research to find the best advice and parts to use, but well worth wading through the information.  Hobbies are like that!   

Good discussion here!   

Incidentally, when I was considering my first AR, I was very close to buying the Colt 6940.  It has a freefloated quad rail hand guard and add a red dot and it was everything I thought I wanted at the time from my feedback from sites like ARFCOM and M4C.  There's just so much information available on the internet and lots of people who sound really convincing, who I look back now and just have to shake my head.  I did a lot of research before I bought and Hawaii isn't the best place for opportunity to be able to shoot that much before you buy.  Eventually, I just decided to get something and run with it.  I ended up buying a DDM4 V5, so pretty close to what I had in mind when I first started the search. 

I also debating a number of things.  Piston vs DI, Aimpoint vs EoTech, light weight barrel vs standard, etc.  I am the type that needs to try for myself to decide and yup, I ended up buying two ARs so that I could try side-by-side.  Probably wasn't the most cost effective way to learn, but it was fun!  Haha. 

Along the way, some of the best advise I got was whatever I bought, shoot it and shoot it as much as I can.  That and the cost of ammo will likely be much more than the cost for the gun, which is very true in my case.  You really do learn a lot that way, especially in formal training with quality instructors.

Thanks to drck1000 and mauidog, I'm gonna price out a Colt LE6920-OEM2. Any suggestion on a good LGS with competitive pricing?

Thanks to drck1000 and mauidog, I'm gonna price out a Colt LE6920-OEM2. Any suggestion on a good LGS with competitive pricing?

OGC had them in late September.  I'd try there to start.

OGC also had the OEM (OEM1) then as well.

Thanks to drck1000 and mauidog, I'm gonna price out a Colt LE6920-OEM2. Any suggestion on a good LGS with competitive pricing?

http://www.danger-close-tactical.com/Rifle-Colt.html

Dwayne lists having the OEM-1, give him a call or look here, http://www.gunstores.net/about/about.aspx?d=T0rXQ9Joq6U=&u=&g=&z=XLPhMTJ%20vUQ= for the OEM-2

Good discussion here!   

Incidentally, when I was considering my first AR, I was very close to buying the Colt 6940.  It has a freefloated quad rail hand guard and add a red dot and it was everything I thought I wanted at the time from my feedback from sites like ARFCOM and M4C.  There's just so much information available on the internet and lots of people who sound really convincing, who I look back now and just have to shake my head.  I did a lot of research before I bought and Hawaii isn't the best place for opportunity to be able to shoot that much before you buy.  Eventually, I just decided to get something and run with it.  I ended up buying a DDM4 V5, so pretty close to what I had in mind when I first started the search. 

I also debating a number of things.  Piston vs DI, Aimpoint vs EoTech, light weight barrel vs standard, etc.  I am the type that needs to try for myself to decide and yup, I ended up buying two ARs so that I could try side-by-side.  Probably wasn't the most cost effective way to learn, but it was fun!  Haha. 

Along the way, some of the best advise I got was whatever I bought, shoot it and shoot it as much as I can.  That and the cost of ammo will likely be much more than the cost for the gun, which is very true in my case.  You really do learn a lot that way, especially in formal training with quality instructors.

Agreed with what / where you have come. 

I think you probably know that I am over at M4C and I will also be the first to tell people to beware about any online info.  Doing and learning or coming to self realization is often better than just information that is passed on without vetting. 

I am a big fan of learning something in its base configuration and then based off of first hand experience attempt to tailor to suit your needs.  While not all will be correct at least one has a better baseline understanding of the process that they are trying to work through. 

As for formal training with quality instructors, indeed it is worth the price.  One can easily burn up 10X that cost in ammo and not see much improvement.  Unfortunately quality instruction may be hard to find, or not easy for a new shooter to understand who or what organization may have quality instructors and instruction.  But yes it is very much a journey. 

The only thing I'd add about the 6940 is, I never intended to try and improve on the basic components,  If you see yourself swapping out barrels, it's not that easy even with the proper barrel nut wrench and barrel extension tool.  For one-time use, it's cheaper to have a gunsmith do the repair than buy the tools!  There are just too many good things about the quality of the 6940 to let two parts be a deciding factor.  But, as I said earlier, going back in time with today's options, the Colt OEM2 would be my pick over the 6940.   

I also own a 6940 mostly due in part to the pricing I was able to get it at.  It is still NIB.  I have shot numerous 6940's and all of them have shown excellent accuracy for a factory Colt rifle.  If someone has wrung out their own shooting style and the rifle fits, it is a great option.  But for those who are new to the platform, it may not be a good choice, especially since guys like to tinker and treat these rifles like Barbie dolls and dress them up.   Also for a standard configured AR pattern barrel there is no need for a barrel extension tool to swap barrels.  I pretty much almost never use mine for installing or removing an extension.    

I built a Spike's Tactical rifle using a striped upper and lower.  The barrel was from BCM with (supposedly) good quality control.  Didn't bother with head space gauges, and it shoots great.  If you get quality barrels and uppers, the head spacing is going to take care of itself, just as you said.  It's a critical detail to make sure if you use cheaper brands or blems, you should maybe have a gun shop or friend with the proper gauges do a 2 minute check.

This is maybe where some might consider me a bit snobby, but for pricing out there, there is almost no good reason to not go with a good manufacturer over a lesser brand.  Pricing is that close, especially right now.  Also for someone new to this, it is better to use a better brand in order to avoid potential issues, that may screw them up worse.

Getting the proper tools and learning to use them correctly is a big deal in any hobby.  Lots of people are wanting to swap an A2 handguard/sight setup for a free-floated, low profile gas block and free floated hand guard of their liking.  I've seen YouTube videos of young men telling you to cut the A-frame sight off the existing gas block to avoid having to pay for a low profile version -- WHILE IT'S STILL ON THE BARREL!  That's after they have you also cut the delta ring to avoid removing the barrel.  When you try to do things cheap, they can wind up costing more to fix than doing it right the first time.  And you'll then have the tools and knowledge to do another rifle, and another.  If I remember correctly, the torque range is pretty wide for the barrel nut on a standard AR, to allow alignment of the gas tube through the notches in the barrel nut.  I used a torque wrench to make sure I had at least the minimum torque.  I also used quality barrel grease.

Agreed that learning about a hobby is a big deal.  Although this is not a hobby involving rocket science, there are quite a bit of technical points that you can only learn from quality instruction.  And take it from a guy who probably had THE most in depth videos on this topic, youtube is NOT the place to find it.  Unfortunately people learn about this platform from someone that does not have the technical expertise to be teaching it.  Again small things like the correct type of grease and correct torque specs.  Just because there is a spec "range" that may fall within normal MIL-SPEC range, it does not mean that it is optimal.  Again the assembly part is not overly technical especially for someone with mechanical ability, but the troubleshooting of problems can be the hard part.

I probably was the first guy to show on video a carry handle chop or a FSB chop and no it wasn't on the barrel.  Other guys morphed into doing it from there and leaving it on the barrel because they couldn't do the rest themselves.  They have no idea about how much heat a barrel can take and what may happen to it.  This is one example of many things that home DIY guys do.  Hell many people still think to this day that the torque spec on the castle nut is was in inch pounds because an out of date Army tech manual was incorrect for over 10 years and then they wonder why their rifles puke some springs and fall apart. 

Thanks to drck1000 and mauidog, I'm gonna price out a Colt LE6920-OEM2. Any suggestion on a good LGS with competitive pricing?

Like mauidog said, I've only seen them at OGC.  Call around, but I would also check with OGC first.  They seem to be the most reliable with regards to finding and bringing in items that they don't have in stock.  Probably will experience a delay for a while due to SHOT. 

You can also search online and find an FFL.  I've done both routes (support LGS and buy online).

Agreed with what / where you have come. 

I think you probably know that I am over at M4C and I will also be the first to tell people to beware about any online info.  Doing and learning or coming to self realization is often better than just information that is passed on without vetting. 

I am a big fan of learning something in its base configuration and then based off of first hand experience attempt to tailor to suit your needs.  While not all will be correct at least one has a better baseline understanding of the process that they are trying to work through. 

As for formal training with quality instructors, indeed it is worth the price.  One can easily burn up 10X that cost in ammo and not see much improvement.  Unfortunately quality instruction may be hard to find, or not easy for a new shooter to understand who or what organization may have quality instructors and instruction.  But yes it is very much a journey. 

Yeah.  A while back I mentioned the "finding the signal through the noise" and that was what I remembered from a learning experience in wading through online information.  I haven't been on M4C that much.  I'll swing by from time to time, but not too often.  When I do to back, I always find it interesting who is still posting regularly and who has been banned. . . Sort of like watching reality TV.   

Yeah.  A while back I mentioned the "finding the signal through the noise" and that was what I remembered from a learning experience in wading through online information.  I haven't been on M4C that much.  I'll swing by from time to time, but not too often.  When I do to back, I always find it interesting who is still posting regularly and who has been banned. . . Sort of like watching reality TV.   

I hear you my friend.  I appreciate some of the consideration that M4C and some other sites have given to me, but I too find myself visiting less.  I am trying to become a bit more interactive here locally as I find my situation a bit more conducive these days.  Hopefully I can bring some clarity in the signal and not just be a part of the noise.