What is a billet upper/lower and why is it so good?

[MrLogan]

I'm seeing a lot of things about billeted uppers and lowers for the AR. What exactly does that mean, and why is it supposedly so much better than your standard lower and uppers?

[JPglee1]

Billet means its carved from a solid chunk of forged aluminum, using a CNC machine.

Cast means its liquid aluminum poured into a mold and allowed to cool (I.E. Its cast in place, its finished when the mold is opened)

Billet/Forgings are generally stronger, but heavier and more expensive to produce. Cast lowers are CHEAP and incredibly light, but also not as strong.


J

[bwiese]

They're mostly 'trendy'.

There's little to no reason to have one. If you need more weight in a match rifle, put a $15 Bushmaster lead weight in your A2 stock's storage compartment.

Forged lowers may resist cracking, etc. better than billet - esp if you had a KaBoom (high primer, double charge, etc.)

[Sig226]

Means that it was "cut" from one piece of metal. There way no heat/forging/casting done on a billet lower.

Is it better- Not on your life. Some look "sharper" on the cuts, and bevels, however some have been reportedly "too tight", or too perfect.

The few i have seen look VERY nice though. They don't have that firearm feel though, they feel more like tools.

Dave

[JPglee1]

Oh yah, I wanted to add... the lower doesn't have much forces acting on it, its the UPPER that contains all the forces for the most part.

I know a guy with a cast AR and a billet AR and they both work well.


J

[mailman]

http://www.cncgunsmithing.com/projects/AR45lower.html

.

[MrLogan]

Wow, thanks for the answers. Looks like there's no real advantage to them. I think I'll keep the extra money and buy more regular lowers.

[luvtolean]

Means that it was "cut" from one piece of metal. There way no heat/forging/casting done on a billet lower.

Actually, that is not explicitly true.

For example, POF uses 7075 T6 which is a heat treated aluminum stock. It is heat treated in it's "billet" form. They don't necessarily need to retreat after machining. (though they can if they're looking for certain properties)

In general here are some benefits to billet:

1) You can use a material you could not normally cast into the shape you want
2) Very tight tolerance control
3) Allows a company to make something of a shape/size they may not have forging or casting tools to make it with
4) Allows for interesting shapes that as cast or forged may not have

5) For guns, you can buy 80% stuff from low volume companies that wouldn't set up to forge the parts otherwise. (like above)

I've been meaning to pick up a set from POF, I love the billet look.