308 which upper fits which lower ?

[Thorax]

I'm in the building phase of my life

I want to build something to take the place of my PSG, it's going into to long term storage for the monetary reasons.
I'm looking to build a AR platform 308....but....I keep hearing issues of this upper won't fit this lower and failure to feed and failure to fire and blah blah blah problems.

I don't need problems, and I DO NOT want to buy a pre-built rifle. I am more than capable (2112)and want to build my own.
I won't lie...I am unfamiliar with a ar10-p308 platform, and I see there have been problems with everyone being on the same page with specs of fit and function.

Can anyone post saying that X upper fit to X lower....or say that X upper did not fit X lower ?

There really needs to be a database of this somewhere.
I registered just to ask this stupid stuff :|

 

[Nihonjin]

Re: 308 which upper fits which lower ?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Thorax</div><div class="ubbcode-body">There really needs to be a database of this somewhere.</div></div>
There is. http://www.ar15.com/forums/topic.html?b=3&f=62&t=378850

 

[Badshot308]

Re: 308 which upper fits which lower ?

That's a good link. It shows what will and won't work with the Armalite AR10. However,there are many other manufacturers of the 308 AR type rifles and there is no real standardization among them. There are three different mags being used,four if you count the G3 mag lowers. Some designs are DI,some piston,some with side charging handles. The majority of the manufacurers are using the KAC SR25/DPMS pattern mags. Everyone is doing there own thing. You'll need to do some careful research before you start purchasing parts for a build.

 

[ORD]

Re: 308 which upper fits which lower ?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Nihonjin</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Thorax</div><div class="ubbcode-body">There really needs to be a database of this somewhere.</div></div>
There is. http://www.ar15.com/forums/topic.html?b=3&f=62&t=378850 </div></div>

That thread is a good starting point, but as observed, it deals with the Armalite AR-10 and not the other platforms available. Here is a link to the General 308 AR FAQ Section that should address many of your questions and give you a good starting point for your consideration:

http://www.ar15.com/forums/topic.html?b=3&f=121&t=413443

 

[LoneWolfUSMC]

Re: 308 which upper fits which lower ?

What I would suggest is just sticking with the same manufacturer for upper and lower.

There are two main groups to look at. You have the Armalite pattern and the KAC/DPMS pattern. Both use different magazines and barrel nuts.

I went with the AR10 because at the time the DPMS was the only other viable option and I DID NOT like the feel of the DPMS. Make sure you get to handle them before you choose. That was the instant decision maker for me.

AR10 magazines are only available from Armalite. You can get a "five pack" for $150. There are several options for KAC/DPMS magazines. Some work, some don't. M14 magazines can be used in a AR10 in a pinch, but must be modified for the mag catch and bolt hold open to function.

If I was going to go DPMS/KAC pattern I might look at Iron Ridge Arms or CMMG for my receivers. For AR10's you can go Armalite/Eagle Arms or Noveske.

If you are building a custom it's really just going to come down to what magazine system you want to use. If you are pushing the limits of COL then you may want to check that in each magazine I know AR10 magazines will allow a longer COL than Magpul. I don't know what the max COL is for a steel DPMS mag.

I did not mention the Rock River Arms .308 because it uses a different magazine setup and is not compatible with any of the others. Remington's .308 is just a DPMS of a different color.

Here is the almost complete build up of my AR10. It was really simple and is a fairly accurate rifle. As it's wearing in it's starting to chase the accuracy of my M700.

http://www.8541tactical.com/precisionar10.php

 

[Thorax]

Re: 308 which upper fits which lower ?

I saw that build up you're doing LoneWolf.
It looks real nice but you've got the barrel tightening part wrong.
You use the forward thread sleeve to set the moment of torque on the barrel instead of backing off the nut to get the gas port to line up....know what I mean ?

 

[LoneWolfUSMC]

Re: 308 which upper fits which lower ?

Brother the way I did it on the site is exactly the way the directions that come with the handguard say to do it.

I am not sure if you are misreading or misunderstanding what I wrote.

 

[Thorax]

Re: 308 which upper fits which lower ?

No, I understand what you're doing and I really mean no ill intents in saying to do it a different way....I just would like to see a fellow shooter get it not just right, but get it perfectly right.

If you do decide to try again, back off the nut about 90 degrees rotation and then turn the forward sleeve in another ~roughly~ 45 degrees, then recinch the main nut.
You'll notice that the gas post will now align differently.
You'll have to make some temporary marks (a paint pen works perfectly since it is easily removable) and experiment untill you get exacly the right torque at the exact right position of the gas port, without backing anything up to compensate.

You should never have to back up to get it right as that will screw the pooch on your torque, and that torque is VERY important.

If you need confirmation of that, pull the barrel on most any factory rifle made and you'll see that they use locktite or thread sealant of some sort or another.
With 50-60 k psi going on in a chamber things can work loose quicker than you think....and that is without taking into consideration a bolt slamming into the thing.

But I digress...
I have found ZERO relevant data to my original question.
It seems no one really cares how thier own branded upper fits to thier own branded lower.
Noveske even states no fit guarantee with thier uppers.

All I really need is a bloody serial number...
Guess I can hit the metal yard and pick up a block of 7075 T-651 and get busy.
It's not like it's brain surgery.

All I really wanted to do was have Lilja build me a brrel to my specs and run it....is that really asking too much ?

 

[LoneWolfUSMC]

Re: 308 which upper fits which lower ?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Thorax</div><div class="ubbcode-body">If you do decide to try again, back off the nut about 90 degrees rotation and then turn the forward sleeve in another ~roughly~ 45 degrees, then recinch the main nut.</div></div>

Actually this is the way I did it. I just went back and re-read my steps and I left one out.

Prior to wrapping the Mounting Block with Tape it should have read "Turn in Barrel Nut until it contacts the barrel shoulder."

My apologies, I will correct the page shortly.

However, it really doesn't matter as long as you end up with the correct torque and the gas tube hole lines up.