AR15/10 parts interchangibility

[1Luv4SF]

Im right in the middle of an LR308 build. I have the upper receiver, lower, barrel, and a few odds and ends. I get confused on which parts are the same as 15 parts. Example: Is a buttstock that is advertised and for an AR15 the same as an AR10? Its hard to find certain AR308 specific parts online but hella easy to find AR15 parts. I need to know which of the following is specific to .308 or interchangable... Thanks!!
-handguard/quadrail
-buttstock
-buffer tube
-gas block
-trigger

[triggs75]

Most of everything you want to know about the differences is here:

http://www.ar15.com/forums/t_3_62/378850_AR10_FAQ_and_information_Small_Update_APR_2010.html

[1Luv4SF]

Thanks for the link but I'm unsure of which information applies to my build. The link is all about Armalite pattern .308s.

[Nathan Krynn]

I'll try to answer this. Yes not all parts are interchangeable and really it takes a lot more knowledge and research on a 308 type AR.

-handguard/quadrail

You have to match the threads for the upper to the rail. The DPMS, AR-10, and AR-15 threads are all different.

Next you have to match the rail height. Again there is the AR-15, Ar-10, new DPMS, and old DPMS.

So on this one it is company by company.

-buttstock

Other then the PRS (there is one for the .308's and the AR-15's) all stocks I have ever seen are the same.

-buffer tube

This is the hard one. I have seen a few ways to do this and it will depend if it is rifle (fixed stock) or carbine (collapsible) and I have seen a few ways for each.

Fixed- use an AR-15 buffer tube and the DPMS LR-308 rifle buffer and spring.
collapsible-
1) use an AR-15 buffer tube and a DPMS LR-308 carbine buffer and spring.
2) To throw you off I have seen an Armalite Ar-10 buffer tube which is a little longer then the AR-15. Then an AR-10 buffer spring and AR-10 carbine buffer. There AR-10 buffers are so close to AR-15 it is not even funny.

I have seen more variations on this whole buffer tube/buffer/spring for the .308 AR's.


-gas block

Same as AR-15 and the size you need depends on the diameter of the barrel.

-trigger

The stock triggers are the same as an AR-15 but if you get a match one then it needs to be rated for .308. Match triggers use lightened springs and some for the AR-15 will not ignite the primers on the .308.

[1Luv4SF]

Thanks for all that good info. Btw, I bought the TM308 lower and it's great. Now since TM doesn't make 308 uppers, which uppers from other companies fit the best? I want as tight a fit as possible. Is DPMS the best? The JD Machine upper I have has a good amount of play between the receivers.

[Nathan Krynn]

No problem. The only tricky one there is the buffer tube as seriously I could list more ways but I don't to overload you.

What stock are you wanting to use? Maybe with that I can lead you in a good direction.

As for the uppers it is for DPMS uppers. Fulton uses DPMS parts so those work. I have heard (not tried personally) that SI defense works really good too but have heard from one person who had to stone the rear lug. I have never used the JD machine's. Long story short it is made for DPMS receivers.

[1Luv4SF]

I'm hoping to use a LMT Sopmod stock

[1Luv4SF]

So if I buy a RRA 2 stage or Giselle trigger those would have to be 308 specific?

[triggs75]

So if I buy a RRA 2 stage or Giselle trigger those would have to be 308 specific?

the RRA 2 stage and the geissele SSA are just fine. I have the SSA in mine

[1Luv4SF]

How is the Giselle? I've only used 2 stage before.

[Seesm]

Most of the lpk parts are the same except the take down pins and the bolt release (its been a lil bit since I checked and its late)

[Speedpower]

Thanks for all that good info. Btw, I bought the TM308 lower and it's great. Now since TM doesn't make 308 uppers, which uppers from other companies fit the best? I want as tight a fit as possible. Is DPMS the best? The JD Machine upper I have has a good amount of play between the receivers.

I installed a DPMS upper on my TM308 and the fit is perfect, it is tight enough to not have any play at all.

[triggs75]

How is the Giselle? I've only used 2 stage before.

The geissele SSA s a two stage trigger. It is very crisp and a clean break