The Difference in 308 Upper Receivers and What We Need to Know

Posted by on June 12, 2016 . 15 Comments.

I love my 308 builds! They are my babies! I can spot them a mile away, but then again, it is my business and I love what I do.

More often then not I get calls from my clients trying to figure out what type of lowers they have and what will fit their 308 lowers. While there are many manufacturers out there and I, by no means, know all of them, the confusion around the topic of what 308 lower will fit with what 308 upper receiver is immense! That's why I decided to share my thoughts around this subject with you - to make the life of my 308 guys easier.

In my opinion, there is one simple rule to remember - there are two types of 308 upper receivers, HIGH PROFILE and LOW PROFILE. These two are very different and NO - you cannot match high profile with low profile and expect it to work!

HIGH PROFILE - This is your original, the "old" version of 308 upper receiver. It has a 3/16" wide top portion where the charging handle is installed and .210 tang.

  • Known Manufacturer - Aero Precision. Yes! Aero's uppers are high profile and will not work with low profile stripped lowers. Aero's manufacturing is impeccable and is very economical in comparison, but Aero upper will fit perfectly with Aero stripped 308 lower and you are limited to that! There is little or no flexibility to interchange.
  • 308 Lower Match for High Profiles - Usually will fit with Gen 1 and LR DPMS. These are your original 308 stripped lowers (FFL required). 

LOW PROFILE - This is the new and most current version of 308 upper receivers, usually referred to as DPMS style and DPMS compatible. Slicker in design and more versatile in use, they have a 1/8" wide top portion where the charging handle is installed with .150" upper tang. The beauty of these babies is the ability to mix and match various manufacturers with ease and not being stuck to just one product. Though more expensive with original purchase, in a longer run, it is more economical choice to use because of it's versatility.

  • 308 Lower Match for Low Profiles - Any Gen 2 308 stripped lowers should work together! In addition to stripped lowers (FFL requirement), you have the flexibility  to use 80% 308 lowers that are usually manufactured in Gen 2 style and mill your 308 lower yourself. Note: 80% Arms, even though state Gen 1, they are used for low profile. Gen 1 is just their internal generalization.
  • Tricky one - Palmetto State Armory. In my experience, I find that Palmetto's 308 uppers will fit most low profile Gen 2 stripped lowers from other manufacturers but won't work with 80% ones unless these 80% from Hells Fire Armory (perhaps there are others out there but I am not claiming to know all). On the other hand, Palmetto's 308 stripped lowers will work with Moriarti Arms 308 low profile uppers!

​So here we go. One simple rule to follow with only few exceptions to remember! One word of advise, when you're purchasing your parts from various sources, see on the measurements and what will match up. If you're in the market for the new 308 complete upper assembly, inform your source of what type of lower receiver you have so they can build your 308 upper assembly properly. This way you will be able to enjoy your new toy immediately upon it's arrival to your door steps!

Hope you enjoyed your read. If you have any questions or suggestions, please don't hesitate to contact me at Moriarti Arms.

United we stand!

Juliya Weisbrot

Moriarti Armaments


Tags: Moriarti Arms, 308 lower, 308 upper, AR-10 kits, AR-10 kit, AR10 Last update: July 22, 2017

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