Yet Another Guy Needs Help Matching Diff Brand Upper & Lower...

[Unarmed Sheep]

Alright, I know the deal with AR-10 _style_ rifles. They aren't just a bunch of Lego pieces that all fit each other like AR-15s. I've never been in a situation where I couldn't eventually find the answer I need if I sat down and searched all the different forums for a few hours, but this time is different. This time I'm working on a 308 AR... I had to pick a site and make an account for this one.

 

I've got a completely factory built DPMS lr 308 with the 24 inch bull barrel. It's the first style with the taller rail, no dust cover, etc. I want to get a 16 or 18 inch complete upper that I'll be able to drop straight onto my existing lower. Who all sells uppers that are compatible with my lower? Also, I believe some uppers come with a BCG and some don't depending on the brand/package/whatever. Which (if any) of these brands of uppers will be compatible with the BCG from my original DPMS upper? Can someone please either help me or share a link to a page that gives a definitive answer to my specific question? I know the gen 2 uppers won't work with my lower but did DPMS change anything between the high rail and low rail guns that would prevent you from being able to mix and match those lowers and uppers or is the rail height the only difference? I think I read something somewhere about a possible issue with the charging handle clearing the buffer tube, but I don't remember exactly which brands and types they were referring to.

After discovering how crazy the AR-10 _style_ rifle world is, I'm quite worried about ordering something that won't work for me. I've read all the stuff explaining how so many brands have different specs for their parts and that's why I'm hoping to just buy the complete upper and be done with it instead of building my own.

I've spent hours googling and reading but so many answers are conflicting and I'm just about ready to just say screw it and not do anything with this stupid thing. I wanted the 16 inch from the beginning but once I got into the store and started looking at all the different models I lost focus, acted on impulse, and purchased a gun on the complete opposite end of the 308 AR spectrum. That was a good 8-10 years ago and I've barely used the rifle I bought because it wasn't what I wanted or needed.

I KNOW a million people have asked a million different questions about this topic, but I'm tired of searching for answers only to read where someone else said the opposite 2 min later. I'm lost, so I'm asking my question myself. Thanks for any help & sorry in advance for beating the dead horse...

 

 

[DNP]

@survivalshop seems to have a fair bit of knowledge on DPMS. A lot of others do too, but let's see if tagging him can draw his attention to this one.  

 

Editing to to add he hasn't been on in over a week. Hope all is well with him. 

Edited January 17, 2019 by DNP

[Matt.Cross]

5 hours ago, Unarmed Sheep said:

I want to get a 16 or 18 inch complete upper that I'll be able to drop straight onto my existing lower. Who all sells uppers that are compatible with my lower?

That's a long list my friend. DPMS- compatible parts are probably still the predominant share of aftermarket options with Armalite pattern bringing up a very close second, IMHO. 

Fortunately for you, there's a really easy way to narrow down the possibilities; the way the upper and lower receiver meet. The receiver pattern for DPMS is a 90° continuous radius at the rear of the upper and lower receiver. The Armalite pattern consists of a receiver cut on a straight angle, with tangent radiuses at both ends.

DPMS:

Armalite:

Anything that has the radiused upper receiver is DPMS patterned. 

[DNP]

I think his questions stems from the fact that some may fit, and function, better than others. We always recommend using sam manufacturer upper and lower, but we know there are plenty out there that can and do work fine together. We have also seen cases where things didn't match up perfectly. I can't site specifics, which is why I am refraining from supplying and answer. I'll let someone who's actually done it chime in. 

My guess for the OP is that yes, the list is long of options that will do just what you need, but hearing from someone who has swapped "x" brand upper onto their DPMS lower would make me more comfortable in my purchase.  As to the question of the high rail, low rail...the lower should have no difference. All that would matter with the high/low upper is which hand guards you use and potentially which sights. You shouldn't see a difference in the lowers at all.