AR15.Com Archives
 6061 v 7075
DrewColt  [Team Member]
2/14/2012 9:49:04 PM
I am about to purchase a lower and need some help with the material. The two options are 6061-T6 and 7075-T6.

The 6061 has the engravings I would prefer, and is $50 cheaper.
The 7075 has engravings I would be okay with, is $50 more, and is stronger.

My question is how much stronger? Will the pins wear into oblong holes eventually on the 6061?

It will not be a SHTF/HD/go to gun. However, I am going to SBR this lower, so longevity is important (and the $50 is not so important).

So school me. Which would you recommend I choose?
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Z1500  [Team Member]
2/14/2012 11:08:32 PM
I would never ever SBR a 6061 lower. Ever.
Why cheap out $50 on something like that?
DrewColt  [Team Member]
2/14/2012 11:46:51 PM
I'll take that as "it's considerably weaker." I figured I should do the 7075. I just wasn't sure how big of a difference there was between the two.

As I said, the $50 isn't really important. My preference of markings is the only reason I was considering it.

Combat_Jack  [Team Member]
2/15/2012 12:28:04 AM
They didn't survive service in Vietnam. I don't know if that means they are completely unsuitable for use but it means I wouldn't get one.
RogueSpear2023  [Member]
2/15/2012 12:47:04 AM
7075-T6 is about 50% stronger than 6061-T6 . But it is less corrosion resistant and harder to weld. I used to work for aluminum extrusion and machining company, we uses 6061 for a lot of things that required welding such as trailers, boats, electronic parts, most of the firearm parts were made out of 7075, but they did have cheaper line made of 6061.
cms81586  [Team Member]
2/15/2012 1:19:11 AM
Why not just spend the extra $20 and pick up a PSA lower? They're machined from 7075-T6 aluminum forgings and they're cheap enough. Just sent in a F1 to SBR my lower without any apprehension.

CMS
ziarifleman  [Team Member]
2/15/2012 1:25:48 AM
I will not even consider a lower properly made if it's not 7075-T6.
DrewColt  [Team Member]
2/15/2012 10:10:39 AM
Originally Posted By RogueSpear2023:
7075-T6 is about 50% stronger than 6061-T6 . But it is less corrosion resistant and harder to weld. I used to work for aluminum extrusion and machining company, we uses 6061 for a lot of things that required welding such as trailers, boats, electronic parts, most of the firearm parts were made out of 7075, but they did have cheaper line made of 6061.


Originally Posted By Combat_Jack:
They didn't survive service in Vietnam. I don't know if that means they are completely unsuitable for use but it means I wouldn't get one.


Thanks guys. This is more what I was looking for than "no don't do it."

I'm not going with a PSA lower because they don't offer a 9mm lower that takes Glock mags. There are limited quantities ready to go, and the one I wanted was only in 6061. Function over form for me though, I'll be getting the 7075.
notso  [Team Member]
2/15/2012 10:25:10 AM
I dont understand the big issue between the two.

Weve got lowers made of plastic now! Either aluminum will be plenty strong for the small (comparatively) force an AR lower sees.
scottmon  [Team Member]
2/15/2012 11:42:10 AM
I'd think a set of anti-rotational pins would make it a moot point with either material
Cholla  [Team Member]
2/15/2012 8:39:41 PM
Originally Posted By notso:
I dont understand the big issue between the two.

Weve got lowers made of plastic now! Either aluminum will be plenty strong for the small (comparatively) force an AR lower sees.


+1
Joenavy85  [Team Member]
2/15/2012 9:49:18 PM
If it's good enough for 308, it's more than good enough for 5.56.
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RogueSpear2023  [Member]
2/15/2012 9:52:28 PM
I honestly don't think it will make a lot of difference between the two, but the 7075-T6 is stronger. I mean how much stress is really put on the lower in a non military environments.
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