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View Full Version : Help me pick a 20" upper for use with a Trijicon TA31RCO-A4CP


tenpercentfirearms
09-17-2008, 5:09 AM
Ok, here is the deal. I am a gun dealer and I can occassionally spend a large sum of money on guns I don't need, all on company credit. So here is my latest project.

I want to use the Trijicon TA31RCO-A4CP (http://trijicon-inc.com/User/parts/products1.cfm?PartID=476&back_row=4&categoryID=3) to put on a 20" upper.

Initially I was going to the really cheap Armalite 20"er I got back on some super sale they were having a while back, but I stalled and yesterday I sold that upper. Plus the more I thought about it, the more I think I want a 1/7" twist.

So my first impression is to go CMMG.

http://cmmginc.secure-mall.com/shop/index_auto.php?shop=1&cart=1251229&cat=27&

Scroll down to the bottom of the page.

First choice, Government Profile or MedCon Profile?

I do not need a front sight post, so I am just going to block it. So which block should I choose from their pull down menu?

Then I got to thinking, why not put a nice rail on it? So help me choose a rail other than YHM. I have YHM rails in the shop and I think I would at least want a Daniel Defense, but what do you think about the other options? What about a micro gas block with a Troy 13.5"? That sounds kind of nice.

I would probably put a Tango Down Vertical Grip on it, so I am good there. I also don't think the eye relief on the TA31 series is all that great so I do not plan on doing BUIS. This baby will rely on the ACOG and nothing else.

So reply in this format

#1: Government or Medcon
#2: Gas Block
#3: Rail System

Sure I am a gun shop owner and I should know what I want, but hey, why not live vicariously though me everyonce in a while. Plus I don't carry everything so I value your input on something I might not be trying. Plus why not offer something special to those that help me out? I won't say what it will be, but I will contact you by e-mail and see if we can't swing a special deal from CMMG while we are at it.

Thanks Crew!

tophatjones
09-17-2008, 5:34 AM
My two cents:

If it were me, I'd want a rifle that's relatively lightweight, well balanced, and has BUIS, just in case.

1. Govt profile. The med con adds a few ounces of weight, and more importantly, it adds it to the front of the rifle. You'd need to add more stuff in the stock to balance the rifle. However, the lighter barrel may be less theoretically accurate and it may be more prone to POI changes due to heat.

2. Standard gas block. I'd use this in conjunction with a BUIS for some rugged iron sights. However, since you are not using a BUIS, I'd get the micro.

3. Daniel Defense FF rails. These are very lightweight at around 13 ounces. The rails can be a significant source of forward weight and can make the gun front heavy. If you choose the lightweight DD rails, you'll need less items in the stock to balance the rifle.

YMMV, and good luck!

shark92651
09-17-2008, 7:46 AM
Wes,

My favorite upper I own is a CMMG 20" MedCon. It's a little on the heavy side, but that is mostly due to the rifle length YHM forearm that is on there. I almost always shoot this rifle off a bench with a Harris bipod so the weight is fine for me.

I know the 16" MedCon CMMG barrel is 5 oz heavier than the gov't profile. The 20" will be a little more (I don't have any in stock right now or I would weigh them for you and tell you the exact difference - oh, and you may have to wait a bit - they have been out of the 20" barrels for awhile).

Since it sounds like you will be shooting off-hand - my suggestion: 20" CMMG Gov't Profile with the DD Lite Rail, DD gas block, and the Smith Vortex hider. That will be a very nice upper.

Edit: Oh snap, 2,000th post :D

Paratus et Vigilans
09-17-2008, 9:32 AM
Easy.

1. Medcon
2. DD low profile gas block
3. DD 12.0 light rail

:)

P.S. The ACOG I bought from you also lives on an upper w/o BUIS. Funny that you are thinking of doing the same thing. Great minds?? :D BTW, my ACOG build has a fluted SS barrel, which I really like - - you might want to consider getting a fluted barrel for yours and then building the upper around it - - maybe one from Randall or even from John Holliger back at WOA. Also consider a .223 Wylde chamber to go with that 1/7 twist. (Look at me, giving YOU build advice - LOL!)

tenpercentfirearms
09-17-2008, 6:02 PM
Alright, I just sent White Oak an e-mail. We will see what they say and if they cut a dealer discount.

Bowser
09-17-2008, 6:04 PM
COLT! (http://www.specializedarmament.com/index.php?p=catalog&mode=search&search_in=all&search_str=colt+20&x=0&y=0)

SuperSet
09-17-2008, 6:40 PM
1. 18" 1/7 Govt Profile barrel - Cuts down on the weight. And a 20" barrel doesn't buy you that much more velocity or accuracy. You will still have a rifle length gas system for reliability. Of course, this depends on how far you are planning to sling lead but IIRC, the 82nd was going to use something very similar for their DMR rigs.

2. VLTOR or DD low profile gas block - It'll fit under your handguards but it probably doesn't matter too much since there's nothing too sexy about a gas block.

3. LaRue 12.0 or JP VTac handguard - I love that all the newer-style LaRue rails have an integral sling swivel mount and don't spin free like YHMs. As for JP, it's a cost savings and you don't have rails where you don't need them.

Just my .02 for your new coyote blaster! It's so much easier to spend someone else's money. :)

tenpercentfirearms
09-17-2008, 6:47 PM
1. 18" 1/7 Govt Profile barrel - Cuts down on the weight. And a 20" barrel doesn't buy you that much more velocity or accuracy. You will still have a rifle length gas system for reliability. Of course, this depends on how far you are planning to sling lead but IIRC, the 82nd was going to use something very similar for their DMR rigs.

2. VLTOR or DD low profile gas block - It'll fit under your handguards but it probably doesn't matter too much since there's nothing too sexy about a gas block.

3. LaRue 12.0 or JP VTac handguard - I love that all the newer-style LaRue rails have an integral sling swivel mount and don't spin free like YHMs. As for JP, it's a cost savings and you don't have rails where you don't need them.

Just my .02 for your new coyote blaster! It's so much easier to spend someone else's money. :)


This isn't a coyote blaster. It will be a gun built around an optic. So we need to stick to 20" because that is supposedly what the ACOG is calibrated to. Really this is my long range tactical gun. I could in theory use it for coyotes, but I already have a Bushmaster 20" V Match with a 4.5-14 power Nikon on it and it is already a great coyote gun.

This build is just a "Man I love Trijicon so I am going to build a rifle to put under a TA31RCO-A4CP" build.

I will check out the Larue and JP rails too.

Maybe I will end up piecing one together! I haven't built one all the way up yet, but I have installed rails and I know that is pretty much all you have to do. I would have to brush up on the headspacing thing a bit.

Nah, I will probably get a complete upper so I won't have to worry about it.

SuperSet
09-17-2008, 7:20 PM
This isn't a coyote blaster. It will be a gun built around an optic. So we need to stick to 20" because that is supposedly what the ACOG is calibrated to. Really this is my long range tactical gun. I could in theory use it for coyotes, but I already have a Bushmaster 20" V Match with a 4.5-14 power Nikon on it and it is already a great coyote gun.


Ah..good point Wes. That BDC is pretty nice.

BTW, when you mention building an upper around an optic, it reminds me of the A-10 Warthog. An airplane built around a cannon. :17:

Good luck on your build!

TMC
09-17-2008, 7:28 PM
My first question would be what are you going to use it for and go from there. If you just want it to look the part then get any cheap upper with a rail system and all the widgets you think look cool on it. If you're going to use it get a quality barrel that will last and give good accuracy. If you going to compete get a good barrel thats light to mid weight with a smooth hand guard so you can prop on things for stability. Just my .02 as I have a few guns that look the part that don't get shot and some that look the part and get used allot.

tenpercentfirearms
09-17-2008, 7:36 PM
My first question would be what are you going to use it for and go from there. If you just want it to look the part then get any cheap upper with a rail system and all the widgets you think look cool on it. If you're going to use it get a quality barrel that will last and give good accuracy. If you going to compete get a good barrel thats light to mid weight with a smooth hand guard so you can prop on things for stability. Just my .02 as I have a few guns that look the part that don't get shot and some that look the part and get used allot.

All my guns are for show because I am so busy selling them that I have no time to use them!

The smooth part makes sense for three gun. I could always put some rail covers on the bottom of the rail too. I definitely want a vertical grip.

Lets see what White Oak says and if they balk, then I am going to go CMMG. This isn't really going to be a bling gun with a ton of gadgets on it. Real simple. A2 stocked lower, NM trigger, 20" upper with rail and vertical grip, and ACOG.

I guess I want that Marine look.

chuck762
09-17-2008, 8:53 PM
I tired a 20 inch heavy barrel in a A4 clone build. By the time I added the rail (ras M5) it felt too nose heavy. Yeah, the rail isn't the lightest but being a clone of a military rifle it is what I went with. I have since switched to a gov. profile and it is much more balanced.
I am using a TA11F on mine.

http://img.photobucket.com/albums/v506/chuck1/DSC02769.jpg

ar15barrels
09-17-2008, 9:59 PM
Are you going to be shooting the exact AMMO that the optic is built around?

If not, you can load your own to match the trajectory, but using a different bullet.

For example, I have a TA01NSN.
It's setup for M855 from a 14.5" barrel.
It just so happens that 55gr M193 type bullets loaded to 2950fps will match that trajectory and I can hit to 500+ accurately with my Acog as long as I keep the velocity right.
I run an 18" barrel so I have to run quite a mild load to keep my trajectory right.
I think my pressures are around 45,000 PSI or so.
Much easier on the rifle and the brass too.

torsf
09-17-2008, 10:11 PM
1) Since you are going for the ACOG - medcon w/ vortex flashhider
2) Micro gas block or the pri flip front if you were going to have BUIS
3) Since no BUIS Larue 13.2 rail (protect the gas block). Altho, this image has been haunting my dreams lately (12 omega rail, have the 7 inch and love it):

http://www.danieldefense.com/img/product/92a39fdfd4fba3b7972fc2ece2145712.jpg

ar15barrels
09-17-2008, 10:14 PM
Low profile gas block.
LaRue 13.2
Govt profile barrel (rail adds weight already, don't make the barrel too heavy too)

tenpercentfirearms
09-17-2008, 10:14 PM
From Trijicon's website: (http://trijicon-inc.com/faq.cfm#f21) 03. What bullet was used to calibrate the ACOG scopes?
The TA01, TA11, & TA31 (.223) were designed for the 5.56mm, 20 inch barrel, 55 grain bullet, and M16/AR15 carry handle mount. The TA01B & TA11C(.308) were designed for the 7.62mm, 20 inch barrel, 168 grain bullet, and M16/AR15 carry handle mount. The TA01NSN was designed specifically for the US Special Operations Command SOPMOD M4 Carbine. To meet their requirements, the reticle bullet drop compensator and range finding stadia lines were based on the trajectory of the 62 grain bullet from a 14.5 inch barrel, flattop mount (Picatinny rail Mil.Std.1913).

--------------------------------------------------------------------------------

04. Does bullet weight and/or barrel length effect the reticle bullet drop compensator and range finding stadia lines?
The real issue is not the bullet weight or barrel length, but muzzle velocity, ballistic coefficient, and the distance from height above bore. The difference in trajectory from bullet to bullet or barrel to barrel is usually less then the MOA thickness of the stadia lines.
That is a relief. I was wondering if they were actually 62 grainers or something. I have plenty of 55 grain ammo and can always get more.

My next question is I have a whole case of Q3131A. I probably shouldn't shoot that 5.56mm ammo out of a .223 wylde chamber should I?

ar15barrels
09-17-2008, 10:18 PM
My next question is I have a whole case of Q3131A. I probably shouldn't shoot that 5.56mm ammo out of a .223 wylde chamber should I?

http://ar15barrels.com/gfx/jeez.jpg

How many times have we covered this already?

5.56 is fine through a Wylde chamber.

tenpercentfirearms
09-17-2008, 10:23 PM
http://ar15barrels.com/gfx/jeez.jpg

How many times have we covered this already?

5.56 is fine through a Wylde chamber.

I need it again. I used to think it wasn't OK until I had a customer point out the RRA website that said it was OK. So now you are helping educate me so I can stop asking this question and start spreading the correct answers.

Relax! :D

Paratus et Vigilans
09-17-2008, 10:23 PM
My next question is I have a whole case of Q3131A. I probably shouldn't shoot that 5.56mm ammo out of a .223 wylde chamber should I?


From what I've read, I believe the .223 Wylde chamber will eat 5.56 ammo just fine, but you'd best check up on that yourself to be sure. I only run handloads in my 20" 1/7 WOA upper with the .223 Wylde chamber (77 gr. and 80 gr. SMK BTHP over 23.5 gr. of Varget), and have never fed it anything else, with the exception of some Black Hills 77 gr. red box match ammo early on, before I started handloading. Ask John Holliger, he'll know for sure. Of course, Randall will probably answer with authority before I even get this posted. :)

Paratus et Vigilans
09-17-2008, 10:25 PM
What'd I tell you. Randall got there firstest with the mostest. :)

tenpercentfirearms
09-17-2008, 10:25 PM
Of course, Randall will probably answer with authority before I even get this posted. :)

You must be a slow typer.

Paratus et Vigilans
09-17-2008, 10:26 PM
You must be a slow typer.

Indeed!

ar15barrels
09-17-2008, 10:26 PM
I need it again. I used to think it wasn't OK until I had a customer point out the RRA website that said it was OK. So now you are helping educate me so I can stop asking this question and start spreading the correct answers.

Relax! :D

For your (and really your customers) benefit, read through my "how it works" write-up.
Pay special attention to the material concerning chamber dimensions and headspace.

www.ar15barrels.com/prod/operation.shtml

You will be a better AR owner if you grasp all the concepts presented there.

ar15barrels
09-17-2008, 10:28 PM
What'd I tell you. Randall got there firstest with the mostest. :)

I'm actually working on a personal record for number of posts in one day.
I am just over 135 right now.
I need to break 165 before midnight.
Probably not going to happen becaause I keep answering REAL posts instead of just making BS posts.

Young Version
09-17-2008, 10:34 PM
I would recommend giving White Oak a call rather than e-mail...I spoke to them a little more than a week ago and they said they were having troubles with their server.

On the plus side, I had my upper in my hands a week after I ordered it...and it wasn't built yet when I ordered it :eek:

randy
09-17-2008, 11:39 PM
Add some class to your stable and buy a JP.

ar15barrels
09-17-2008, 11:58 PM
Add some class to your stable and buy a JP.

You shooting at Piru sunday?
If not, come to WEGC saturday night.
Or, do both...

tenpercentfirearms
09-18-2008, 4:49 AM
Add some class to your stable and buy a JP.

Crap, I forgot about JP too! Now I have to research them as well. This is not the simple project it once was.

tenpercentfirearms
09-18-2008, 6:05 AM
I checked JP. Nothing there fits what I am looking for.

dlouie87
09-18-2008, 10:08 AM
This is going to be a nice project :D

randy
09-18-2008, 11:39 PM
Then try www.mstn.biz

elSquid
09-19-2008, 12:30 AM
ADCO?

http://www.adcofirearms.com/acc/productLine_.cfm?brand=Adco%20Custom&product_category=Complete%20Uppers

-- Michael

tenpercentfirearms
09-19-2008, 5:27 PM
New question.

I currently have two AR15s lowers built up with A2 Stocks: Spike's Tactical ST-15 Infidel (has a Bushmaster 20" upper on it) and Centermass Tactical OLL Coyote (has a LMT MRP 6.8 18" on it). I also have a Centermass Tactical CALGUNS Lower built up with an A1 Stock (has a AA .50 Beowulf on it). All have RRA NM Triggers.

So should I just use one of those and not build up another lower, should I use one of my three stripped lowers in the safe (DSA ZM4, POF I Forget the Model Number, or Stag STAG-15), or if I get a CMMG upper also get a CMMG lower?

I am thinking I might just build up one of those three in the safe. Honestly, all three of the lowers I have would look good with a 20" ACOG build. I would probably want to use the STAG or the DSA and save the cool looking POF for a rainy day.

ar15barrels
09-19-2008, 5:36 PM
New question.

I currently have two AR15s lowers built up with A2 Stocks: Spike's Tactical ST-15 Infidel (has a Bushmaster 20" upper on it) and Centermass Tactical OLL Coyote (has a LMT MRP 6.8 18" on it). I also have a Centermass Tactical CALGUNS Lower built up with an A1 Stock (has a AA .50 Beowulf on it). All have RRA NM Triggers.

A lower is a lower is a lower...

tenpercentfirearms
09-19-2008, 5:45 PM
A lower is a lower is a lower...

Not true. A lower I already bought and paid for is a lower. Buying another lower is more money I probably don't need to spend.

So basically even if I get a CMMG upper, I might just throw it on one of three I have. The only bad thing is I have to buy more parts to build it up. Oh well, that is money well spent.

randy
09-19-2008, 11:51 PM
Yo 10% quit spending money on uppers and come to Piru and shoot a match with what you've got.

It's a great way to meet the shooters, have fun and see how your equipment works.

Then decide on what upper you want.

The match is this Sunday starts at 9ish.

tenpercentfirearms
11-21-2008, 4:47 AM
Ok, I am back onto this project again. I am still thinking of going CMMG.

I am pretty sure I want a longer than 12" rail so I can have a micro gas block and no front sight. CMMG gives me a Troy option at 13.5" Randall suggested the Larue 13.2", but CMMG doesn't give me a LaRue option.

Does anyone have an experience with the Troy vs. LaRue rails. Money is not an object, rail quality and weight are the only considerations.

Let me know!

Army GI
11-21-2008, 6:03 AM
Ok, here is the deal. I am a gun dealer and I can occassionally spend a large sum of money on guns I don't need, all on company credit. So here is my latest project.

I want to use the Trijicon TA31RCO-A4CP (http://trijicon-inc.com/User/parts/products1.cfm?PartID=476&back_row=4&categoryID=3) to put on a 20" upper.

Initially I was going to the really cheap Armalite 20"er I got back on some super sale they were having a while back, but I stalled and yesterday I sold that upper. Plus the more I thought about it, the more I think I want a 1/7" twist.

So my first impression is to go CMMG.

http://cmmginc.secure-mall.com/shop/index_auto.php?shop=1&cart=1251229&cat=27&

Scroll down to the bottom of the page.

First choice, Government Profile or MedCon Profile?

I do not need a front sight post, so I am just going to block it. So which block should I choose from their pull down menu?

Then I got to thinking, why not put a nice rail on it? So help me choose a rail other than YHM. I have YHM rails in the shop and I think I would at least want a Daniel Defense, but what do you think about the other options? What about a micro gas block with a Troy 13.5"? That sounds kind of nice.

I would probably put a Tango Down Vertical Grip on it, so I am good there. I also don't think the eye relief on the TA31 series is all that great so I do not plan on doing BUIS. This baby will rely on the ACOG and nothing else.

So reply in this format

#1: Government or Medcon
#2: Gas Block
#3: Rail System

Sure I am a gun shop owner and I should know what I want, but hey, why not live vicariously though me everyonce in a while. Plus I don't carry everything so I value your input on something I might not be trying. Plus why not offer something special to those that help me out? I won't say what it will be, but I will contact you by e-mail and see if we can't swing a special deal from CMMG while we are at it.

Thanks Crew!

I know that someone already suggested it, but go for the White Oak Service Rifle upper. Ask them to use an A4 receiver instead of the standard A2.

ar15barrels
11-21-2008, 7:52 AM
I am pretty sure I want a longer than 12" rail so I can have a micro gas block and no front sight. CMMG gives me a Troy option at 13.5" Randall suggested the Larue 13.2", but CMMG doesn't give me a LaRue option.

Does anyone have an experience with the Troy vs. LaRue rails. Money is not an object, rail quality and weight are the only considerations.

The LaRue rail is a superior design to the Troy.
The troy just clamps on to a factory barrel nut and they are rarely as straight/true as a LaRue.
LaRue has dedicated barrel nut system of it's own and a much nicer anti-rotation feature.

Order the parts and assemble it yourself.
If you are not able to build AR uppers, I charge $25 to put together a box of parts you send me.

There are also Daniel Defense rails in 13.5" or 14" available through Ranier.

aplinker
11-21-2008, 8:34 PM
DD or LaRue, Wes. The Troys are ok, but not up to par.

LaRue rails are beautifully executed, but the feel of DD is really nice. Either way you won't be disappointed.

tenpercentfirearms
11-22-2008, 9:00 AM
There are also Daniel Defense rails in 13.5" or 14" available through Ranier.

I didn't see them on the website. Do you have anymore info? I will go check out Ranier.

I have a barrel wrench so I am thinking as long as they send me a barrel and bolt that have been matched, I should be fine.

lakai
11-22-2008, 3:51 PM
http://i37.tinypic.com/2s67syw.jpg

http://i34.tinypic.com/2ppnehu.jpg

ar15barrels
11-22-2008, 4:51 PM
I didn't see them on the website. Do you have anymore info? I will go check out Ranier.

I have a barrel wrench so I am thinking as long as they send me a barrel and bolt that have been matched, I should be fine.

The 14" models are a special run for Ranier.
http://www.rainierarms.com/?page=shop/detail&product_id=1076
Not listed on Daniel Defense's site.

DD handguards require special wrenches.

tenpercentfirearms
01-07-2009, 9:13 PM
Ok, I ordered a 20" from CMMG with I think the lightweight profile (or government). I ordered it with a micro gas block and a Vortex and told them to ship it without handguards. Daniel Defense told me by e-mail that they are going to be making 14" handguards so I will see them at Shot Show and see about getting one. I know the CMMG will be a while anyway.

I will of course post pictures when I can.

I think I will build this bad boy on my Kaiser Defense lower.

tenpercentfirearms
07-31-2009, 6:28 AM
The CMMG 20" finally arrived yesterday!

Only one problem: no Daniel Defense >12" rail. THey had made some, but there will be no more.

So I got to thinking, why not just use a DD 12" rail and just leave the micro block exposed? You have about 2 hours to convince me that is a bad idea, because I feel like building an upper today while the ATF finishes their audit.

tenpercentfirearms
08-15-2009, 8:24 PM
I went ahead and built most of this thing up today.

http://i53.photobucket.com/albums/g52/elrojo14/guns/DSCN0285.jpg

Mega Billet Lower
RRA A2 Fixed Stock
RRA NM 2 Stage Trigger
Bullet Button
Hogue Grip
CMMG Government Profile 20" Barrel
Daniel Defense M4 12" Rail
CMMG Micro Gas Block
Vortex Striker Flash Hider
Tango Down QD Vertical Grip

My partner Dean took my ACOG TA31 A4 sight and put it on his AR57. I am trying to get him to bring it back and put a Reflex on his gun as that 20" A4 calibrated ACOG is just about worthless on a AR57. When I get it back, we will get some more pictures and test it.

foxtrotuniformlima
08-15-2009, 8:38 PM
Looks sweet Wes!

tenpercentfirearms
10-04-2009, 7:36 PM
So I see on the gun shop credit card a charge for like $700 something from Daniel Defense. What could that be?

Imagine my surprise when in comes some DD AR15 Lite Rails...14"!!! They said they weren't going to make anymore, but apparently they did or they found three in the back for me! Nice.

So after work today, I did this!

http://i53.photobucket.com/albums/g52/elrojo14/guns/DSCN0361.jpg

I also had a EOTech 557.G23RTS in the shop too that I had been eye balling so I decided to take one home.

http://i53.photobucket.com/albums/g52/elrojo14/guns/DSCN0359.jpg

However, I am still going to go for the ACOG on the 20" build and I think the EOTech looks much better on the DD M4 Carbine. I just need to get a MI Flip Up Rear for it on Tuesday and the DD will be good to go!

http://i53.photobucket.com/albums/g52/elrojo14/guns/DSCN0360.jpg

Sometimes it is tough being a gun shop owner.

Adrien
10-08-2009, 1:01 PM
Let's see that ACOG!

Adrien