Want to build a solid and accurite 20" upper to put on my Colt MT6400 lower??

[NYH1]

Hi,
I want to buy or build a complete 20" upper receiver setup to put on my Colt MT6400 (pre-ban version of the LE6920) lower receiver. I want to make it as accurate as it can be. I will switch back and forth between my factory 16" Colt M4 profile complete upper setup that came with my carbine and the 20" complete upper as often as I want. My current 16" upper setup has my Aim Point Patrol Optic on it.

In my lower I have This...Geissele 2 Stage (G2S) Trigger (http://geissele.com/geissele-2-stage-trigger.html), H2 buffer, stock spring. I'll switch to whichever buffer and spring I have to so the new 20" upper runs rock solid.

Could THIS...BCM Standard 20" Government Profile Upper Receiver Group (http://www.bravocompanyusa.com/BCM-M16-Government-20-Upper-Receiver-Group-p/bcm-urg-gov-20.htm), with a good free floating rail system, a good Leupold Scope and mount along with good ammo be capable of close to 1 MOA at 100 yards off a bench? If not how well do you think this setup could shoot?

Thanks, NYH1.

[Ryno12]

Personally, I'd opt to piece together an upper with one of BCM's 20" SS410 barrels.


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[Eurodriver]

Why do you want a 20" upper? Is the max range you'll be shooting at 100 yards? If so, a 20" is serious excess. Your 16" will shoot just as well at 100 yards as a 20" will. In fact, and I am speaking from experience, your 16" will shoot just as well (maybe even better) than a 20" out beyond 300 yards.

The main issue you're going to run into is, as you said, using a carbine buffer assembly with a rifle gas system. You will (or at the very least should) have to switch the buffer and spring from your carbine buffer to something heavier, like an H3 and one of the many colors-of-the-rainbow Springco springs every time you want to swap uppers. I see you're in NY so I understand why you have to do this. But I wouldn't.

What I really wanted to ask was with respect to your "I want to make it as accurate as can be." You are wasting $450 if you buy that 20" upper. A solid stainless steel 18 or 16 inch upper by a reputable manufacturer will shoot circles around that 20" BCM. All else being equal, an SS barrel with match ammo will shoot much better than a chrome lined barrel with match ammo. To answer your question more directly, yes, I think that 20" might shoot close to 1 MOA at 100 yards with match ammo, a good shooter, and a good optic. But a quality 16" SS barrel with match ammo will shoot much better while being 4" shorter, weighing less, and not requiring a buffer swap.

[NYH1]

I was using the 100 yards and 1 MOA as a basic bench mark. I'll use this 20" upper to hunt small game like woodchucks, Crows, Fox, Coyote ect. at ranges anywhere from 50 yards out to maybe 400 yards. I thought about starting the whole project with This BCM 20" SS410™ SAM-R Barrel with Rifle Length Gas (stripped) 1/8 Twist (Ionbond Black) Barrel (http://www.bravocompanyusa.com/BCM-20-SAM-R-SS410-Barrel-with-Rifle-Length-Gas-p/bcm-ss410-samr%20brl%201%20ibb.htm) and build a complete upper half around that.

I already have a few 16" carbines and uppers so I want to build a 20" upper half anyways, so that's not going to change. Here are a few things I plan on doing, nothings cut in stone though-

I want a fixed pinned on front sight (for that barrel it'll be .750").
Centurion Arms C4 Rail System.
BCM M16 auto BCG & Bolt.
The same type Troy flip up "same plane aperture" rear sight that I have on my 16" Colt.
I want to be able to use a bipod of some sort (this will be new to me, never used one before).
Some type of Leupold, probably a 3-9x40 or maybe 4-12x40 maybe with a AO.

Thanks, NYH1

[Eurodriver]

That SAM-R barrel, free floated, is a much better choice if you want serious precision. You won't be disappointed.

[Ryno12]

[QUOTE=NYH1;1936558 I thought about starting from the whole project with This (http://www.bravocompanyusa.com/BCM-20-SAM-R-SS410-Barrel-with-Rifle-Length-Gas-p/bcm-ss410-samr%20brl%201%20ibb.htm)[/QUOTE]

That's the one I used on my 20" precision build & I'm very happy with it. You'll have to be patient if you want the ion bonded black barrel though. They occasionally become available. I see the standard SS barrels are available right now if the finish doesn't matter to you.


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[NYH1]

I just realized that the fixed front sight I planned on using needs to have the holes drilled in it for the pins to the barrel.

NYH1.

[223to45]

To the OP,

I was planning on something similar , but what I decided was to just start with the BCM 20" complete upper, when I can out shoot that ( ie; when I am more capable then the rifle ) I will upgrade the barrel .