AR 308 lower parts kit confusion.

My lovely wife got me a Matrix Arms AR 308 receiver set for an early Xmas present. The specs call for an Armalite or DPMS A style lpk. I’m trying to find such kits, but they only say DPMS or Armalite. Can I use them?

Can you call Matrix on Monday and report back what they recommend?

Did your receiver set ship with pivot/takedown pins?

I've read a lot about the Matrix receiver and I too am confused on which kit to buy.

Mine arrives Wednesday and I'm sure ALOT of people will be asking this question after the sale that was run on them.

Blaze that trail for us -!-

It did have the two pins.

I'm not really irritated about figuring out what to use because I got for $170, and their receivers are what Ruger uses.

According to the description on Matrix Arms website, the 308 receiver set is compatible with DPMS and Armalite A series lower parts kits. So, any DPMS 308 lower parts kit will work as well as any Armalite lower parts kit that specifically says A series. If you google "Armalite A-Series lower parts kit" or "DPMS 308 lower parts kit" you will see the options. Armalite A series LPK's are listed as "A10LRPK" and B series LPK's are listed as "10LRPK", that is how you can tell them apart.

You also need to be sure to buy a rail that has the DPMS "high" profile.

Aside from the LPK I'm curious which barrel nut is used (Armalite or DPMS)

I believe Matrix changed them all to DPMS recently, if so I plan to stick with a DPMS LPk

I gotta get mine in hand to see...

Ahh, I read it wrong. Thanks for the clarification. I think I'm going to just use the DPMS.

I started on it last night, and found that LaRue's AR-10 and AR-15 APEG grip will not fit. Magpul's A-15 MIAD grip will though. The LaRue trigger went in fine, which was more important than the grip.

Alissa Farris with Matrix Arms had the following to say today via telephone:

1) Upper uses a DPMS barrel nut
2) Lower parts kit is DPMS or Armalite 'A'
2a) She is unsure why a lower parts kit is not offered on their website, they've discussed it but to date you can't buy one from them

I received my Matrix Arms receiver set today from the Primary Arms Black Friday sale - it looks very nice for the money spent.

It has a threaded bolt catch , wish I knew that when I ordered since Primary Arms lists part no. LR-12-308 for $ 3.99

Now if you try to order just the pin it is plus shipping and over $ 10.00

I hate pissing money away so I'll probably just make one.....



EDIT: stopped by ACE Hardware on the way home , a 6-32 socket set screw was too big.

This lower takes a 4-40 size threaded bolt catch screw!

Or

You can probably just drive in the standard roll pin and be done with it.

I'm not sure anybody even sells a 4-40 bolt catch screw....

Thanks for the information. I'll probably start installing parts in a couple weeks.

Ignore the above post referencing 4-40, when I went to ACE hardware I think a larger size was mixed in the 6/32 bin.

Today I went back and ensured I grabbed a 6/32 and it's nice and tight.

These are readily available online so grab a bolt catch screw when you order or buy one after the fact .

More to follow on the build , the lower parts and upper parts kit arrives today

The magazine catch recess is deeper on the Matrix Arms vs other 308 (AR10) this is causing the magizine catch to protrude past the inner wall of the magazine well and contact the magazine which Increases resistance on inserting and releasing the magazine....

I also tried a Aero Precision 6-32 bolt catch screw and it bottomed out before being threaded all the way into the receiver body

This is all for now

I can confirm that the Aero Precision kit works perfectly if you don't mind the bolt catch screw sticking out a little. I'll have to get one from Primary Arms when they come back in stock. I don't have any issue with changing magazines though.

Also, if you want to use a LaRue APEG grip, you have to use the AR-15 version. The AR-10 version won't seat.

I saw your YouTube video. Nice work sir. I'm hoping to have it finished by the end of the year. I have a couple other AR-15's I've only shot a couple times, I want to spend time with for now. Having trouble deciding which company to get a 7mm-08 barrel from too.

I liked my barrel from McGowen Precision

Brownells does. Not cheap though. But at least you can see what it is supposed to look like.
https://www.brownells.com/rifle-parts/bo...B2F99A3F3D34870

Thanks for the link that ended up being the wrong size

It’s a 6-32 screw