Theres a lot of confusion surrounding .308’s and many people would like to better understand the differences between AR10 vs DPMS vs SR25.

Everyone knows that AR15 fits everything AR15 – and this is due to the mil-spec standard in place for the last 60 years. So the AR15 platform is pretty self explanatory. But with .308’s, everything becomes much more convoluted. Let’s shed some light on the AR15’s more complicated cousin.

There is no mil-spec for “AR-10”, or anything based on the AR-10

Matter of fact, the actual Armalite AR10 is it’s own beast, and is not in line with any of the 308 industry standards. The down side of this specific situation is that “everyone” refers to anything large-frame-not-ar15 as being “AR10” – First mistake. The only AR10’s out there are the ones specifically made by Armalite. However, the industry has dubbed all of them as “AR10”.

Even we do it – you can see on our website that we refer to any large-frame product as a “DPMS style 308 LightWeight AR10 Lower Receiver”. And we do that because if we don’t, people looking for our products on the internet will never find us.

So, there is AR10 (Armalite), DPMS and SR25 formats for 308 parts at this time. The SR25 was developed by Eugene Stoner (same guy who did AR10) but he designed the SR25 correctly. In other words, he made the Pin holes a standard size (9/32 vs 0.277, which is Armalite), and the angle is a specific number. Several years later, DPMS made the same Lower from SR25, but made it with a radius in front of the stock tower like the AR15, instead of the angle.

So, there is a great deal of commonality between SR25 and DPMS – which use most if not all of the same parts. But not completely the same everywhere...

The SR25 Upper follows the “High Profile” Picc rail standard, which is the original Armalite spec of 2.06″ tall for the Upper. The DPMS Upper started out as “High Profile” but then went to “Low Profile”, which is 2.000″ tall. You can “see” this difference in the thickness of the tang at the rear of the Upper just above where the Charging Handles seats. This is the reason why you see references on 308 Uppers and Hand Guards to “High Profile” or “Low Profile”. You just have to make sure they are the same.

Our SR25 style 308 Upper follow the “Low Profile” standard, as does our DPMS style 308 Upper. The only actual difference between our two Uppers and Lowers is the Angle vs Radius in front of the stock tower. Everything else is the same.

The reason why you need both the Upper and Handguard to be either Hi or Lo profile is because ALL 308 Uppers have a Bore Centerline of 0.750″ above the parting line from the Lower. ALL 308 Uppers have a 1-3/16″ Bore diameter, so ALL 308 Uppers use the same DPMS/SR25 BCGs. NOT all 308 Uppers have the same Barrel Nut threads. Armalite is 1-7/16 x 18 tpi, and DPMS/SR25 are 1-7/16 x 16 tpi. ALL 308 Barrel Extensions are the same – so that they ALL fit in the bores of ALL 308 Uppers. The main differences are the BN threads (so your barrel nut), and the Hi vs Lo profile – and that’s about it.

All manufacturers that make these parts should be following the same “industry standards”

Though, many of them don’t. A couple of easy examples – LWRC sells what appears to be an SR25 profile, but it is not – different angle and Pins. The PSA PA-10 appears to be DPMS low-profile, but it is not – the Bore Centerline of their Upper is 0.050″ lower than ALL other 308 Uppers, so their Upper won’t mate to anyone else’s Lowers….except ours will!

KAC and LMT (and LRWC) are really good at the “proprietary” parts thing. Don’t buy those components, unless you want to buy ALL of their components. But there are several manufacturers that follow the basic rules on industry standards for parts. Most of it is just buying and checking (trial by error).

Our 308 Uppers and Lowers will use DPMS Gen 1 compliant parts – as long as they are actually “DPMS Gen1” compliant. Once again, DPMS uses Pins that are not 100% DPMS Gen1 compliant, ie. the Upper and Lower will Pin but it will look very awkward.

Any of the available 308 barrels should easily work with either of our 308 Uppers – just make sure that you have a DPMS/SR25 Barrel Nut.

The 308 side of the industry is, for the most part, in sync and works well among various manufacturers. But there are manufacturers that do the proprietary parts thing mostly to force you to use only their parts for your builds. There’s a reason why KAC, LMT and LWRC sell $4-5k 308 Rifles. Its because they are the only places that you can get those specific components and rifles.