7075-t6 vs 6061-t6 in a lower receiver

[Sgt.Begood]

Anyone can guide me in this!
is there a real difference in those two aluminum grade 7075-t6 vs 6061-t6 in a lower receiver?
NEA use 6061 and other Co. use 7075.
I'm

 

[Throttle_monkey1]

7075 will have a higher tensile strength and better corrosion resistance. They'll have roughly the same modulus of elasticity. Both should be fine for an upper or lower as neither is a high stressed component.

 

[CanAm]

There was an excellent thread on this subject a few months back.

The result was the 6061 was more than good enough.

 

[Slug870]

Jesus... here we go again...

 

[SPRTN308]

I figure if you can make a hobby AR lower out of plastic then who gives sh!t right?

 

[trevj]

7075 will have a higher tensile strength and better corrosion resistance. They'll have roughly the same modulus of elasticity. Both should be fine for an upper or lower as neither is a high stressed component.

Uhhh... Close.

7075 will corrode faster than 6061, once the protective coating is removed. The zinc in the alloy gives it strength, but it does rot when left to it's own devices in the weather. Not an issue, unless you were planning on burying it in the yard unprotected, or leaving it hanging in a tree in the rain. For months.

6061 can be welded, if need be, and will bend a little more than 7075, typically, before breaking.

All this info really affects the guys who are making the lowers, more than the guy using them. Price of bar stock, or forgings, price of tooling and the wear on them, that sort of stuff.

7075 will take a higher polish, if chrome-like shine is your goal.


Either is good.

Cheers
Trev

 

[P0WERWAGON]

what are you planning on doing with the AR to make that a buying factor? your gunsafe is under the ocean?

 

[SPRTN308]

your gunsafe is under the ocean?

One more reason to go with plastic.....

 

[fireball]

7075 will increase your high speed, low drag maneuvers in front of the mirror.

 

[Epoxy7]

One thing to note is that DPMS also uses 6061 on some of their products. Their consumer grade stuff uses it. Their higher end products use 7075. Ultimately both will work fine. But like many things with AR rifles the specs used for the military versions are favoured.

It won't make a difference for use with most of us. The thinner corners on the NEA design for the mag well probably play a larger part in concern for strength over the grade of aluminum. The grade of aluminum realistically plays more of a role in resale as it isn't to the same specs as the military version.

One other thing to consider. There are forging to spec AR lowers for around the same price. For billet the NEA is the cheapest Ive seen. NEA should grab a Hera lower to see how it's done. Then offer an upscale version with the specs most are looking for.

 

[1965BJS]

If a 140mph Marathon jet boat hull can be made of 6061 material, run in 2" of water and last through years of race use, it will work fine as a lower for any firearm!

 

[Sgt.Begood]

Ok,thanks CanAm!

 

[Mirk]

Needless to say when it comes to AR lowers there is a lot of conjecture on this subject…

In my opinion a 6061 billet is adequate and a 7075 forging is ideal…

 

[Sgt.Begood]

Just need a cheap and reliable AR to run in 3Gun match just for fun,i didn't know the difference between 2 aluminum grade.

I'm thinking to get a DDM4V7 or a NEA15 DMR.

anyway thanks for your reply!
Cheers!

 

[fireball]

Buy a Norc and see how long it goes to failure then post about it on CGN, sit back and watch!

 

[dogzilla]

The only thing that really matters is does it have Law Enforcement Only stamped on the side. If it doesn't, it's just no good.

 

[sulisa]

"Buy a Norc"

That's my problem... the damned Norc is still going strong - it would be a lot easier to replace parts or whole if it was failing... and believe me, I've tried to kill it!

 

[CanAm]

found it

http://www.canadiangunnutz.com/forum/showthread.php?671871-6061-further-thoughts-and-new-information

 

[Throttle_monkey1]

Uhhh... Close.

7075 will corrode faster than 6061, once the protective coating is removed. The zinc in the alloy gives it strength, but it does rot when left to it's own devices in the weather. Not an issue, unless you were planning on burying it in the yard unprotected, or leaving it hanging in a tree in the rain. For months.

6061 can be welded, if need be, and will bend a little more than 7075, typically, before breaking.

All this info really affects the guys who are making the lowers, more than the guy using them. Price of bar stock, or forgings, price of tooling and the wear on them, that sort of stuff.

7075 will take a higher polish, if chrome-like shine is your goal.


Either is good.

Cheers
Trev

I should have clarified. The reason 6061 was abandoned in favor of 7075 for milspec was due to intergranular stress corrosion cracking in humid climates like vietnam.

6061 is easier to weld and machine, and 7075 has a higher UTS, yield strength and is harder when both are hardened to T6 or T651 condition. Again for an unstressed lower or upper I would be comfortable with either. Also 6061 is easier to anodize.

 

[misanthropist]

I should have clarified. The reason 6061 was abandoned in favor of 7075 for milspec was due to intergranular stress corrosion cracking in humid climates like vietnam.

6061 is easier to weld and machine, and 7075 has a higher UTS, yield strength and is harder when both are hardened to T6 or T651 condition. Again for an unstressed lower or upper I would be comfortable with either. Also 6061 is easier to anodize.

That is true...BUT the 6061 that Colt was using was forged, and FORGED 6061 is prone to the specific type of corrosion they encountered in Vietnam.

Most (in fact all that I can think of) 6061 stuff today is billet, and is more resistant to that type of corrosion than the forged 7075 Colt transitioned to to deal with the corrosion issues they encountered.