Building a DPMS in .308?

[kcofohio]

I have a set of stripped upper and lower in DPMS. I have a few questions for clarity, so that I don't buy useless to me parts. This will be for an occasional paper target shooting from 100-300 yds. I'd be happy if I can be within a 10" pattern at 300 yds. And this will probably be a slow build over a years time.

LR-308 and the DPMS are they same? My understanding is that PSA got involved with the DPMS and they have a 2nd generation now. But the original DPMS is considered the LR-308, yes?

Barrels: my understanding is that barrels are interchangeable between the AR 10 and DPMS. Am I correct? Only the barrel nuts are different. I got a measurement of 1 7/16-16 for the threads.

How picky is the gas system? Plans are for a Faxon Duty series in 20". Rifle length gas tube. With DI, is an adjustable block necessary, especially in the event of going between .308W and 7.62x51 ammo?

I have read that some bolt carriers can dig into the threads on the lower. What do I look for to get the correct carrier?

Most all threads and articles that I found are 5-10 years old. I'm not sure if better specs are out there.
Thanks for all input.

 

[12Bravo20]

There is no industry standard when it comes to large frame AR's. You best bet is to make sure to use parts that are made for the DPMS lower and upper you have. With the upper you will also need to check to see if it is a high or low upper. This is how high the rail is on top. This will only effect your choices of handguards.

When it comes to barrels, as long as the manufacturer(s) state that they are for the DPMS pattern then you will be fine. The same goes for bolt carrier groups.

Mostly what differs is parts such as the take down pins, magazine releases, etc. The DPMS style large frame receivers use the same triggers as AR15's use.

I have read that some bolt carriers can dig into the threads on the lower. What do I look for to get the correct carrier?

Yes that can happen but it is usually caused by using the wrong buffer length. Make sure to use the correct buffer and buffer tube for large frame lowers. There are a wide variety of buffers and buffers tubes available. An example is using a standard AR15 rifle length buffer tube, you will want the correct r308 rifle buffer which will be shorter than an AR15 rifle buffer. Best thing is to buy the buffer, spring and tube as a kit so you know it will work.

 

[mcb]

Yes the LR-308 is a DPMS AR-10 and probably the most common of the AR-10's patterns out there. The Armalite pattern is a distant second.

DPMS also made a small frame 308 AR platform call the GII but I don't think PSA has brought that back out though at 2023 Shot Show they said they will be reviving that product line.

Look for parts for LR-308 or DPMS AR-10 and they will most likely work with you receiver assuming you have a DPMS LR-308 and not a DPMS GII. LR-308 uses a 1.25 diameter bolt carrier, GII uses a 1-inch bolt carrier, same diameter as an AR-15 just longer.

 

[kcofohio]

There is no industry standard when it comes to large frame AR's. You best bet is to make sure to use parts that are made for the DPMS lower and upper you have. With the upper you will also need to check to see if it is a high or low upper. This is how high the rail is on top. This will only effect your choices of handguards.

When it comes to barrels, as long as the manufacturer(s) state that they are for the DPMS pattern then you will be fine. The same goes for bolt carrier groups.

Mostly what differs is parts such as the take down pins, magazine releases, etc. The DPMS style large frame receivers use the same triggers as AR15's use.



Yes that can happen but it is usually caused by using the wrong buffer length. Make sure to use the correct buffer and buffer tube for large frame lowers. There are a wide variety of buffers and buffers tubes available. An example is using a standard AR15 rifle length buffer tube, you will want the correct r308 rifle buffer which will be shorter than an AR15 rifle buffer. Best thing is to buy the buffer, spring and tube as a kit so you know it will work.

Thanks for that info! The upper at the tang, where the charging handle comes to rest measures 1/8". So it looks like a low profile. That could have saved me ordering the wrong handguard.

I'll pay attention when and take your advice on the buffer/spring/tube set.

 

[Charlie98]

Best thing is to buy the buffer, spring and tube as a kit so you know it will work.

I'll pay attention when and take your advice on the buffer/spring/tube set.

That was the biggest mistake I made when I was piecing together my last AR-10 build. This was back when parts were a little low on the shelves, so I was trying to piece together parts... and I kept getting it wrong. Buy the KIT... save yourself the headache.

It sounds like you have thought it out well enough. Even though I've built 2 AR-10's, they weren't for me... but I have an Aero upper/lower set upstairs just waiting for me... and my bank account to fill up.

FWIW, I keep looking at sales at PSA... where I can buy a generic complete AR-10 upper for about half of what it would cost me if I went parts hunting on my own. It's really hard to beat the cost on a completed upper unless you are looking for something specific.

Also... a word on magazines.... get them NOW, not later. Just saying.

 

[Robert]

This is my AR308 I recently "finished". It was built from the following parts:
Aero lower
DPMS upper
Aero BCG
Aero AR308 mag button, it's thicker due to their lower design.
Aero 18" stainless barrel
PRS Carbon fiber round float tube
Magpul Moe+ grip
Magpul STR stock
Aero buffer kit including buffer, spring, and tube
Some random AR trigger I had. A LaRue will go in soonish...
Vortex PSG Gen II 3-15 MRAD scope and mount.

Few parts outside the upper and lower are specific to one design or the other. Just make sure it fits DPMS and you are fine. If you have the older low top rail just make sure your handguard matches and you'll be fine.

 

[Charlie98]

Since we are throwing pictures up...

A purpose built AR-10 in .308 I built for my TaeKwon-Do instructor... he wanted something fast and handy for piggy poking...

Aero receiver and Atlas forearm, 16" BA barrel, lots of Magpul...

And a purpose built AR-10 in 6.5CM I built for a friend... he wanted something semi-auto to match his Ruger RPR in 6.5CM. This one was a trick to build because of the parts shortage.

Aero set, Odin 22" heavy stainless XL gas barrel (which works really, really well....) and Odin HP BCG, MI forearm, mystery meat furniture...

 

[bfoosh006]

That was the biggest mistake I made when I was piecing together my last AR-10 build. This was back when parts were a little low on the shelves, so I was trying to piece together parts... and I kept getting it wrong. Buy the KIT... save yourself the headache.

It sounds like you have thought it out well enough. Even though I've built 2 AR-10's, they weren't for me... but I have an Aero upper/lower set upstairs just waiting for me... and my bank account to fill up.

FWIW, I keep looking at sales at PSA... where I can buy a generic complete AR-10 upper for about half of what it would cost me if I went parts hunting on my own. It's really hard to beat the cost on a completed upper unless you are looking for something specific.

Also... a word on magazines.... get them NOW, not later. Just saying.

Magazine wise... 100% get them now. Oregon is working right now to ban ALL higher then 10rd mags.

And PSA uppers and lowers are their own pattern... IE a PSA upper will not fit a DPMS lower. Even the bolt catch is specific to the PSA pattern.

So if someone goes PSA... commit to their uppers and lowers. Various other parts will work with those, ( barrels, triggers , easy stuff )just not the upper and lowers interchanging with other brand uppers and lowers. The whole no / lack of a MilSpec guideline issue for LFAR's. So lots of manufacturers are "just slightly" off to get around patent laws.