I'm about to get hip-deep in the .308AR stuff, and I'll start with the recoil systems, because the biggest problems with functional problems on these large-frame platforms are with the recoil system. Period.
I'll start with some bad information I saw here:
This is because there are multiple options for the buffer tube length/buffer length/buffer weight combo. You did not do your due diligence in ordering. Plain and simple, a buffer tube with the app. 8" internal length requires a 3.25" buffer and appropriate app. 12" .308 roundwire spring or a .308 flatwire spring. Better get an H3 buffer. Carbine length buffer tubes require a 2.5" buffer, H3 or heavy buffer equivalent and the appropriate spring.
There are three major (and many minor) .308AR platforms: DPMS-based, Armalite AR-10-based, and Rock River LAR-8 platforms. The older Bushmaster BAR-10s fall directly, identically, into the RRA LAR-8 platform - they are the same. The RRA is a different animal, completely.
There are three receiver extension depths, in an AR, if you don't talk about carbine recoil systems on the Rock River LAR-8. That gun is COMPLETELY different. The ONLY carbine receiver extension with an internal depth of 8.000" is the RRA LAR-8.
The three other COMMON receiver extension depths are 9 11/16" internal depth (ALL rifle receiver extensions, period, be it AR15 or .308AR). There is NO different rifle receiver extension for "A1" or "A2" - that's a buttstock change, and nothing more than adding a 5/8" spacer to the end of the extension, and a 5/8" longer vented buttstock screw, for the 5/8" longer buttstock on the A2. You add those parts to convert the "A1" to the "A2." That's it. The rifle receiver extension between both, and the internal recoil system parts, are identical. In the AR15, you run a rifle buffer that's 5.900" long, in the .308ARs, you run a buffer that's 5.200" long. The weights in those are different, too.
Carbine receiver extensions:
There are only two. Period, full stop. No more. (Again, we're not talking about RRA here, and their massive differences.) There is an AR15 Carbine Receiver Extension that has a 7.000" internal depth, and there's an Armalite AR-10 Carbine Receiver Extension that has a 7 5/8" internal depth. No more.
The DPMS-based LR-308 runs a 7.000" internal depth receiver extension, and has to be used with a 2.500" buffer, and that is, by far, the most common, prolific, .308AR platform out there. The HUGE problem is that everyone and their brother thinks they can make one - and they often screw it up. In spades. "Whatever" for a spring - even AR15 springs that can't handle the "mass for the ass" of the 308 BCG, nor the recoil difference - buffers that are too light - and more often than not, receiver extensions that they just "want to make..." They THINK they got it right... and they don't. They just throw you a bunch of parts in a box, call it a "recoil system" and think it's good. "It worked in our testing..." Whatever.
Armalite designed and made this rifle - and I'll tell you right now, I don't own a single Armalite rifle. I have alot of the parts, but there is not one single "Armalite" upper, lower, complete gun, in my house. However, there are ALOT of Armalite parts in my house. THEY pioneered it, made it a reality, and know what works. Go tell Eugene Stoner that he's wrong...
The AR-10 was the first rifle - not the AR15. It was fully designed with a 5.4oz buffer, because that was "enough mass to control the ass" and the weight of the BCG, cartridge pressure, and everything else associated with firing a .308 Winchester load from "The AR." 5.4oz buffer. Oh, I forgot the spring - the Armalite EA1095 spring. That is THE recoil spring - yeah, same spring, doesn't matter if you're running Rifle recoil system or Carbine recoil system. Same spring does it for both - with a 5.4oz buffer.
The AR-10 Carbine Recoil System was designed around the buffer and buffer spring - they already had the spring, and it was proven in the AR-10 Rifle recoil system. Turns out the same buffer weight was needed (5.4oz) for both rifle and carbine systems. They made a buffer that was 3.250" long, used tungsten for all three weight that would fit it, and guess what? It was 5.4oz. Now, they had to make a receiver extension that would run that 3.250" buffer - the internal depth was determined to be 7 5/8" internal depth - to run the 3.250" long, 5.4oz carbine buffer, and the EA1095 spring.
Done deal - and it works, every single time, on every single DPMS-based or Armalite-based .308 AR.
Not an 8.000" internal depth carbine receiver extension. Definitely not this 7 7/8" internal depth receiver extension - quoted from the same person that said it should be 8.000" internal... ?...
BTW, back when you ordered, a buffer tube with a 7 7/8" inside depth still took a 3.25" buffer, and a carbine length buffer tube still took a 2.5" 308 buffer.
This struck me as odd, the quote below this - the misunderstanding between buffer weight and "it's overgassed..." It's not "overgassed," my man - it's under-recoiled to a HUGE extent. Tell you what - do an experiment for me. Gut your buffer of everything inside it, and shoot it - you think you see "overgassed" right now? You are REALLY gonna see what you think it "overgassed" if you do that! And it doesn't have a single thing to do with your gas system - which would remain completely unchanged... It's UNDER-RECOILED, with that empty buffer. Can't be refuted, in any single way, right there.
and If you add 1.5oz. to your buffer all your overgassing issues will be solved but if you don't add 1.5 oz to your buffer, the next time you fire your rifle it will fall to pieces in your hands and kill a puppy. Adjustable gas block? Never heard of it.
Regardless, The vast majority of the PA10's reportedly run just fine with an H buffer and the PSA supplied spring.
^^^ On that, right there, I've taken a problem rifle from that company, to fix myself, on my own dime. I paid for shipping to me, I fixed it, and I sent it back, and I didn't ask for a single penny from the poor guy that bought it - he just wanted his gun to run. I made it run, and the only thing I asked for in return was the opportunity to handle it, and see what was wrong in the first place. I diagnosed what I could over the interwebz, and it still didn't work. I requested he send me the gun - and he did. What I gained from that was a vast amount of information on what was being shipped to customers - and what it took to fix it, and really make it run.
What it took, in short, was a complete change of the Carbine Recoil System to the Armalite AR-10 Carbine Recoil System, changing the too-short gas tube to one what was 3/16" longer, and drilling up the too-small gas port (18" midlength gas system barrel) from 0.070" to 0.085". After making those changes, it ran FINE.
My next post in this thread is going to be about gas port diameters, gas port location, and the proper gas tube to use. There are some VERY WELL KNOWN barrel manufacturers that can't get the gas port location right, and think that "gas timing" is just something that isn't important. Stay tuned, and get the popcorn out.
