JT's Matrix Build

[jtallen83]

Well I'm off to a rough start....first all the issues with the barrel being shipped back and forth and no sooner does that get squared away and I'm looking at a rail that has a poor fit;

This is an MI SS rail for an AR-10, I assumed with the Armalite threads that an Armalite rail would fit right. I haven't torqued the nut yet as it sits in the picture so the rail is going to get further from the notches in the nut while the top rail is already hitting. Am I doing something wrong with the installation? This is my first big bore build and first upper so I'm not certain what to expect but I sure expected a closer fit between rail-nut-and receiver.

Do I need to back up and get a different rail, like the Matrix I should have gotten to start with? <dontknow>

 

If this is a common occurrence or normal fit then please tell me to get over it and carry on, I tend to be a little over critical of things I build.

 

If I do need a different rail all is not lost as I have an AR-10 that needs a FF rail. I spent a bunch extra getting rails, covers, and QD swivels with attachments just for this rail so selling it would bite!

 

I was going to throw on an A-2 stock I have and try to function test the bolt tonight but I decided this was enough for one evening :-[

 

I still need to decide on a gas block, I'm thinking I'll go with an adjustable, I'm keeping up hopes Iowa will join the ranks of the sane and allow suppressors soon. What are some suggestions for a quality adjustable gas block?

Edited August 16, 2015 by jtallen83

[blue109]

You say it's not torqued..but is it hand tight? If so it's not going to move much more when you torque it down.

[98Z5V]

Use that crazy purple loc-tite they gave you, and set the barrel to the barrel nut.  That'll hold it in place, and won't require a high torque on those 2 screws. 

[jtallen83]

I did get it real hand tight to line it up the top rail so I'll have to torque with the wrench to the next notch.

 

Looks like maybe I should just ignore the gap and get a gas block ordered aye?

 

Who makes a good one, I've never messed with them?

[98Z5V]

Faxon makes a REAL nice steel lightweight gas block.  REAL NICE.  For me now, it's either gonna be that one from Faxon, or a Geissele Super Gas Block, on everything I make in the future.  The determination of which one it is will come down to the basic purpose of the rifle.

[blue109]

Gap behind the nut looks a little bigger than Normal, but I think you are the only one that will really notice it(because it's yours and we are our own biggest critics) It still looks fine. Long as the nut is torqued and the tube is secure you should be good to go. Looks like the collar was designed wide with some adjustment room to accommodate slight differences in uppers.

[jtallen83]

Faxon makes a REAL nice steel lightweight gas block.  REAL NICE.  For me now, it's either gonna be that one from Faxon, or a Geissele Super Gas Block, on everything I make in the future.  The determination of which one it is will come down to the basic purpose of the rifle.

The basic purpose like most of my weapons is to defend myself and my family from a tyrannical government or other threat if needed. Hopefully coyotes, steel, and paper is all it ever gets unleashed on.

For the gas block I'm thinking an adjustable, lightweight isn't the prime concern, I can't run so I don't need to move fast with it.

[jtallen83]

Gap behind the nut looks a little bigger than Normal, but I think you are the only one that will really notice it(because it's yours and we are our own biggest critics) It still looks fine. Long as the nut is torqued and the tube is secure you should be good to go. Looks like the collar was designed wide with some adjustment room to accommodate slight differences in uppers.

I am a bit anal about this sort of thing.........I imagine once I can get 5 rounds under an inch at 100 yards I'll start to forget about the "big" gap. <thumbsup>

I'm betting the barrel nut will hit the 35ftlbs by the next notch so the look shouldn't change much at all. Guess if it does open up more than I can stand I can go to the local machine shop and have a touch shaved off the top rail end.

It does have a knurled barrel nut so with that, the loc-tite, and the 45 inlbs called for on the two bolts the rail should stay put.

Another months gun budget and I should be shooting this thing!

[guruofhotrod]

Since the top rail on the Handguard/rail is against the front surface of the upper receiver, being able to run the barrel nut further down on the threads

would result in the anti-rotation tabs engaging less into the barrel nut so, it looks to me like you have it assembled as intended by the manufacturer.

 

I am noticing that the ejection port door pin isn't hanging out the front face of the upper as is typical of the large frame AR's - you should double

check to confirm that the pin can't shift forward enough to allow the door to fall off during use <dontknow>

[ChaseFan9]

Hey JT, I knew that sounded familiar! Upon further inquisitations I fount this:

As for the dust cover, I'd have to recommend Strike Industries UDC. It's cheap, lightweight, and fits my Matrix uppers perfectly, anyways. Plus it's the only QD dust cover I've seen, which eliminates the rod and any of those annoying little c-clips

[blue109]

Good eye guru...but he's got it covered.

http://www.strikeindustries.com/shop/index.php/ar-ultimate-dust-cover.html

[ChaseFan9]

Thanks, Blue, great minds, eh? <lmao>

[jtallen83]

Thanks guys, after sleeping on it I can live with the gap. Time to move forward on the build.

I spent several hours this morning looking at gas blocks and reading here, still not 100% sure what way to go but strongly leaning to the adjustable. With the rifle length gas system on the 16 inch barrel it looks like I would only need an adjustable gas block if I go suppressed. I'm hoping I get that opportunity some day, it was real close this year so there is hope and I don't want to switch out the block later if I can get a can.

I didn't really like a few things about the Syrac adjustable, the rear facing screw and the ball and spring setup look like a weak spot for corrosion , fouling, or breakage. I found one I think I like;

http://slrrifleworks.com/index.php?route=product/product&path=57_103_104&product_id=386

It is a little pricy but then it is the only one I have found with the features I like, adjusts at the front, no small parts, easy to clean, and solid adjustments I can keep track of for tuning to different ammo.

Have I overlooked any others with these features???

The last decisions I need to make are stock and buffer system. I'm thinking about using the Armalite carbine tube, spring, and buffer but still haven't ruled out a UBR stock so I haven't ordered it yet. If I go the UBR route I had thought of getting the buffer from Slash but I'm a little concerned that the rifle length gas on a 16 incher might not have enough umph to push a heavy buffer, any input there would be appreciated??? I've read lots of conflicting info on what buffer to use with the UBR?

I may just build it using my Armalite rifle set-up for now so I can at least get a function check sooner than later.

Whoever said "The best things in life are free." never built a 308AR!

 

[blue109]

I'm banking on the rifle gas being ok with a standard weight 308 buffer. I'll try it before I pony up for a heavy just because I have one here. Good thing about the ar10 setup Is you can get a heavy AR buffer and if it doesn't work out in the 308, swap it into a 5.56 gun. UBR is a REALLY nice stock, but it's a pig. great if you are battering doors down but Hard to justify the cost and weight penalty otherwise. Don't think I'll use one again. I love the magpul ACS but sopmods are my go-to stock now. Nothing fancy, pure function.

[jtallen83]

I've got an extra buffer from my Sig PM400 that I put an H3 in and have an H2 in my Armalite M15 so I have an assortment to try from then. Guess I'll get the tube and spring first then see what works out. I have an ACS on the M15 so maybe there is something to be said for consistency.

Is the UBR much heavier than an A2 set-up? 

I was thinking the extra weight might help balance the rifle but I sure don't want the balance point going too far back???

The price on the UBR does make it easier to talk myself out of it.........

[blue109]

The ubr is gorgeous, and nothing is more solid, but it's heavy. Believe the stock by itself is about the weight of an entire A2 setup. you have a 16" with a pretty light float tube so I don't think you need that much ballast to flatten it out.

Just playing devils advocate.

[jtallen83]

I appreciate the first hand info, that's why I love this place, you get the straight shitt here! Odds are I'll go the ACS route and if it feels light in the azz I'll put some lead in that little compartment I've never found a purpose for <thumbsup>

[FaxonNathan]

The basic purpose like most of my weapons is to defend myself and my family from a tyrannical government or other threat if needed. Hopefully coyotes, steel, and paper is all it ever gets unleashed on.

For the gas block I'm thinking an adjustable, lightweight isn't the prime concern, I can't run so I don't need to move fast with it.

 

For those going adjustable, we are good friends with ODIN Works who makes an fantastic adjustable block with click-in place adjustments (from the front, too!)

[Rsquared]

Hey JT. I run a UBR on one of my AR-10 carbines with a lightweight Troy rail. I run one of Slashs' heavy buffers in it (CAR 10 XH). The UBR is a little hefty. But it's worth it (in my opinion at least). You get used to it pretty easy. I love it myself.
 
It also has a PRI adjustable block. Not bad, but it can be a pain in the ass to adjust (adjustment screw is on the side) unless you take a dremel to the rail once everything is in place.


Just the enabler coming outta me.

Edited August 17, 2015 by Rsquared

[washguy]

JT  Ive seen in person the MI rail you have...they look like yours ..... they are light, but I stayed away just because of the exposed barrel nut thingy and the lil gap look...oh well...you need another build anyways    :) Wash

 

http://www.primaryarms.com/Seekins_Precision_Low_Profile_Adjustable_Gas_Block_p/sp0011510031.htm

 

got 3 or 4 of these....less than half of that other

Edited August 17, 2015 by washguy

[survivalshop]

  That gap may just help cool the Barrel quicker & if you remember the JP Hand Guards have a gap also & they look good , I have two , one with the gap & one I assembled with out a gap because it was so close to matching up to the SI Defense Gen II upper.

 

  This is the MI SS on my 16" Tactical Machining Upper , I installed this one to match the Post 2009 ( low )  DPMS rail height , that TM uses.

  

[jtallen83]

The longer I see it together the more OK I am with the gap. 

I'm doing my best to not let budget stop me from ending up with what I want but when I do the numbers on the UBR option with the extras it adds at least a month to the completion date.........wish I could find a rifle with it locally to put my hands on before I made the call. Still a lot of little stuff to get that adds up faster than I realized.

[washguy]

"The longer I see it together the more OK I am with the gap."      Thats what you tell all the ladies!  True dat    :) Wash

[jtallen83]

Any reason this Aero M5 carbine buffer kit will not work on my Matrix build?

http://aeroprecisionusa.com/m5-308-carbine-buffer-kit.html

I was going with the Armalite kit but this is half the cost with the Labor Day sale going on. 

[98Z5V]

^^^  Should work - I think I figured out the problem with it, so it'll need a little file-work on the receiver extension, if I'm right...  Give it a shot, brother, and I'll get details up about the issue/fix.