7.62 lower fit a .308 upper

[Shooter1697]

Hello all,

 

My question is simple I believe. I have a 7.62 80% lower already machined out and ready for the upper.  Will a .308 upper fit my lower or do I need to buy a 7.62 upper.  

Thanks in advance 

 

[DNP]

You are about to have a few more questions. Caliber isn’t the deciding factor in any of this. There are no standards in the 308AR world, so getting an upper receiver that matches your lower will be important. The caliber you choose can be one of many and is mainly affected by the barrel and bolt you install. 
 

What brand is your 80% lower?

[dpete]

3 minutes ago, DNP said:

 

What brand is your 80% lower?

....and pictures!  Pictures of the lower are good.  Show us specifically what you have and what we're talking about.   

[Shooter1697]

What happened was I bought a 5.56 80% lower from 80% lower.com and they sent me a 7.62 lower instead.  Didn't notice it was the wrong one till after I machined it and tried to attach the upper to the lower and it would not go together.  So then I noticed it was a 7.62 lower they sent me not a 5.56. So I contacted them and they sent me the 5.56 one and I assemble my 5.56. Now I want to get the upper and assemble the 7.62 one. Just want to make sure I get the correct one. Here is my 5.56. I can take a picture of the lower when I get home.

[DNP]

If that’s pictures of the gun in question…Looking like AR-15 probably stamped 7.62x39. No, that won’t fit a 308 upper.  

[DNP]

This is the difference in frame size.  See the size of the magazine well?  If the ammo doesn’t fit in a magazine that fits that well, there would be no way to feed it.  It could be argued that sure, you could build a single shot upper for it…but what would that help?

Edited October 25, 2022 by DNP

[dpete]

@DNP    This is his last sentence... "Here is my 5.56. I can take a picture of the lower when I get home."   The pictures are of a 5.56.  We still have to wait for the pics of the 308.

[DNP]

Dammit…well what damn good are pictures of the 5.56?  I guess I quit reading halfway through. Fuk me. 

[blue109]

1 hour ago, dpete said:

@DNP    This is his last sentence... "Here is my 5.56. I can take a picture of the lower when I get home."   The pictures are of a 5.56.  We still have to wait for the pics of the 308.

But if you are expecting a 5.56 lower...and you get a big frame 7.62x51/308 lower....and don't immediately realize that you have the wrong lower...should you really be building guns? 

[dpete]

2 hours ago, blue109 said:

But if you are expecting a 5.56 lower...and you get a big frame 7.62x51/308 lower....and don't immediately realize that you have the wrong lower...should you really be building guns? 

Hmmmm.  Another good question.  I was wondering how a 5.56 jig would work on a 308 lower.  Are finishing jig kits that universal?  

[jim3326]

10 minutes ago, dpete said:

Hmmmm.  Another good question.  I was wondering how a 5.56 jig would work on a 308 lower.  Are finishing jig kits that universal?  

My jig does both but I have to change between mounting plates. I don't believe I could get the two mistaken.

[DNP]

Perhaps the jig came with it?

[Shooter1697]

The jig came with the lower. And yes there is a big difference in size but if you only have the one and u order a 5.56 you would not expect the company to send u a 7.62 in it place. Just saying!!

 I looked at the lower last night and it its stamped. 308/7.62. So sorry for asking a question that I could have answered if I would have looked at the lower. My bad!! 

Have a great day!! 

[DNP]

Don’t leave…trust me, you have more questions. There are different patterns to the 308 frames. There’s a lot of differences and you’ll want to make sure you have one that matches up. Are you planning to build an upper, or buy one assembled?  Does the shop you bought the lower from sell complete uppers?

[Armed Eye Doc]

@Shooter1697there are many things to know besides large frame vs. small frame ARs.  Even if you don't interact, I would recommend that you stick around and read the abundance of information available on the forum before you buy anything.  As DNP said, there are multiple patterns of large frame ARs that do not work together.