I am planning to build my own 16" CAR and was planning to get a cheap cast lower.  Now, after reading many posts about staying away from them, I want to know the disadvantage.  Thanks.

They're brittle.

It's very easy to end up with voids and faults included in the casting that will give it an easy shear line to crack upon.

There ARE high quality castings which do not suffer from these problems, but the "cheap" castings out there are now aren't it.  I've never heard of problems with the pre-ban Essential Arms cast lowers, other than being kind of ugly - but they're plenty strong.  I've heard they were investment cast for EA by Ruger.

I know of several instances of both Olympic Arms and Hesse Arms (now Vulcan Arms) cast lowers cracking right in two while being handled or fired.  At least with Olympic, if it happens to you, they'll replace it free of charge, and you'll probably get one without any faults, if not the first time, probably the 2nd time around.  With Hesse, you'd be SOL.  I've never heard of problems with the DPMS cast receivers - but I don't know how they price out compared to the Olympic and Hesse.

How cheap is cheap?
Are you really saving that much?
Would you really save much over a quality forged Eagle Arms lower from Quantico Arms for $100 (Even $90 is you catch their sales)?

I have seen RRA and other lowers for just a bit more.  Pete in NH has the "US Property" marked RRA's for just a bit more. Sure a Bushy from the factory for $180 is high but you can do better.
Even Numrich (e-gunparts.com) has forged lowers for $100 (Item No. 808820)

I have a cast EA Co. lower and it is nice (and not so ugly if you refinish it), but I went with a low-cost forged lower over a cheap cast one for my last build.

A few dollors more now may save the asprin expense later.

Good luck with the CAR.

Are the Eagle Arms lowers sold by Quantico cast or forged? I just bought one and assumed they are forged.

from the Quantico Arms site:
"ArmaLite never sells ArmaLite branded receivers.  Instead, they sell receivers under the Eagle Arms name.  These receivers are made with the same forgings, on the same equipment and by the same people as ArmaLite receivers.  Features include:
Forged
MilSpec dimensions
Milspec hardcoat anodized "

At $100, I'm trying to justify another one.

I just got an EA lower from Quantico.  You can't beat the price and they are forged.  I believe the marks say "Eagle Arms by Armalite" on the magwell.

I built one rifle on a DPMS cast lower, it was very nice, pretty close to my Oly forged (PCR99) and definitley better than the Oly cast my son bought for his first AR.

Both of them built up without problem, he sold the Oly with less than 100 rounds through it so no telling longevity, my DPMS carbine I ran about 500 through and realy ran it hard without any signs of wear or problems. I know 500 rounds typically isnt much but almost all of those were as fast as could be fired short of bumping and all using 30 round mags.

The Oly cast use to run about $68 dealer and I think I paid around $80 dealer for the DPMS, both were purchased a couple years ago.

I've had a Oly "Plinker" cast lower on one of my rifles for a couple years with no problems. I don't see a difference between it and my forged lowers.

Something to think about...

I've converted Olympic cast lowers into machine guns and they work fine...

yeah, the markings on Eagle Arms lowers are:

Eagle Arms(logo)
Div ArmaLite

Rifle 5.56mm
M15A2
Ser.XXXXX

As previously said, stick with forged peices. With cast, even the best have that miniscule chance of cracking.

BTW not all oly lowers are cast they made cast and forged.

Hun,

Very true, I have an excellant Oly forged lower on my varmint rifle.