I know this has been discussed previously,,no luck in search.
Are there any hesitation in using a cast lower?,,cast upper?
Most M14style recievers are cast and ther are .308 so I don't see any problem.
Is there?

Cast is usually considered garbage.  Don't compare how other weapons are built to the AR, as its apples and oranges.  

For the $20 or less difference, it isn't a savings in the long run.

Are you looking at 80%ers?
I researched this before. What I concluded was that most CAST receivers that broke, broke allmost emideatly (including the story of a guy who ordered a new rifle (can't remember brand) and when he opened the box at the dealer the rear of the receiver with the buffer tube attached was completly broke off, right in the box, straight from the factory!) , soooooo I figure they had flaws in the casting, if it last 100 rounds or so it should last forever. I've built quite a few 80% cast receivers.

Since we are talking about this,what does forged mean?

A forging is a blob of metal that has been heated up and basically pounded into a rough shape in a die.
They take that rough shape and machine away a bunch of metal to end up with a finished lower.

Cast receivers are made more like injection molding with plastic.
There is a mold and it's about 95% of what a finished lower looks like, down to the inside of the magazine well and often the lettering on the receiver.
They squirt metal in the mold and let it cool.
Only minor machining is done, usually the pin holes and some slots.

The easiest way to tell a forged lower is to look at the machining on the front of the magazine well.
If there is a nice wide machined area there, it's likely a forged lower.
If there is a really thin seam there, like you see on molded plastic parts, it's probably cast.
Also, cast lowers can have raised markings while forged lowers will always have machined or stamped markings.

These same things apply to front sight bases.
Forged ones will have the "UP" and arrow mark stamped into the base.
Cast front sight bases have raised markings.

Randall Rausch
www.ar15barrels.com