Anyone use 308.0 AL alloy in lowers

[okiebuckout]

Hello my knowledgeable friends. I found a guy who is building 80% lowers and will let you use his shop to finish out the lower. I went to check them out last night and noticed they seemed extra lightweight to me. Long story short, he uses 308.0 aluminum alloy. I haven't been able to find much info on using this metal on firearms. Can anyone chime in on its reliability on being used as a lower? Thanks for any info.

 

[fletcher]

308 is an aluminum casting alloy, used for permanent mold castings. My opinion is that if cast properly and subjected to effective quality control, it could produce a functional lower, albeit low strength (compared to typical materials).

308 is machinable and fairly corrosion resistant, and pretty castable. As with any casting, there is the chance for significant defects if the foundry doesn't have their act together. Typical strengths are around 16 ksi yield, 28 ksi ultimate - not in the "high strength" range for aluminum castings. To put that in perspective, yield is about 40% and ultimate 62% that of 6061-T6. Typical elongation (measure of how much it can stretch until break) is low as well - 2%.

Are the castings certified to any spec, ASTM or otherwise? That could at least give an idea of the minimum properties and QC requirements.

 

[okiebuckout]

I am not sure on any certifications. I thought I was going to the guys shop, but found out he is milling these out of his closet at home. I didn't get a good vibe about his operations. Needless to say, I didn't buy while I was there.

 

[fletcher]

Sounds sketchy. For a lower that would last and be at least reasonably rugged, wrought would be my first choice, and a high quality casting as second. This sounds like neither. Interesting situation, though. Makes me curious what drove the guy to use 308.

 

[okiebuckout]

Cost more than likely.

 

[berettashotgun]

Plastic lowers are much lower strength than 308 casting alloy lower. They seem to hold up fine to homeowner use..........
I don't know anything about the "308" alloy in use, been around aircraft alloys for quite some time now.
I cannot figure the reason behind this use unless a large mfg was going to make a bunch of lowers and was trying to save a nickle....