i own one SN# 7711 i bought it as a blaster rifle for $600 out the door @ a gunshow
i have had no problems with it so far and this is the first time i have heard of it being poor quality.
whay kinds of problems are people having with there lowers?
why are people saying there shitty?

If it works reliably and it does the job you ask of it  and you are happy with it then there is nothing wrong with it at all.  If it doesn't do any of the above then you have a problem.  

Vulcan is considered to be on the lower end of consistent quality.  Consistetncy is the key here.  You may get one that purs like a kitten but you have an increased chance over other "higher end" brands that you get a turkey.  

All manufacturers screw up--some just do more so than others.  Some use less expensive or less quality parts or manufacturing techniques. And this is typically reflected in the price.

But if it is working, KEEP BLASTING!  

Before it was called Vulcan, the company was known as "Hesse", named after its founder; Robert Hesse. Hesse had a great reputation for selling out of spec crap. I've personally done a refurb on a Hesse receivered FAL that still makes me shake my head and wonder WTF?
Hesse had some great idea's, polymer and Carbon receivers, but was ahead of the synthetics technology necessary for his idea's. A combination of the products failures and Hesse's asshat personallity basically ended the company's retail ability.
Kind of unfortunate, as Cavalry Arms has since had great success with polymer receivers and Bushmaster is doing good with the Carbon's.
Anyways, Hesse folded and was reborn as Vulcan, which has been working to distance itself from its former self.  I have 3 of the Vulcan AR lowers, which are now sub-contracted from the same forging company's as everyone else, and they work fine. I personally like them because of the "soft" charcoal colored anodizing and the lack of a ghey logo.

Vulcan is considered to be on the lower lowest end of consistent quality junk.

fixed it for you.

Seriously, if you have one that works, you lucked out.  Enjoy shooting it.  Very low resale value, but that's like losing money in the stock market.  You only lose it when you sell, its all theoretical until then.  Because of their history of problems, they aren't recommended as it is literally a crap shoot if the one you get actually works or not.  You've already rolled the dice and got a 7.  Just don't plan on buying another and getting the same performance.

The add on to that is their complete lack of customer service.  They don't offer or honor any kind of warranty on their product.  Shooting real ammunition voids it.  On the plus side, if the receiver works, all other parts are user replaceable.

Hesse made cast receivers, which are weaker than forged.  Someone posted a pic of their cracked Hesse lower a few years ago.  That was pretty much the kiss of death.  Though Vulcan’s are now forged (I believe), that kind of history is hard to shake off.

I have a synthetic Vulcan lower that after firing 50 rounds through, shrunk! That's right, shrunk as in magazines would no longer fit in the well etc. A call and letter to Vulcan never resolved the problem so now I have a $80 paperweight and a warning not to buy Vulcan!

It is more appropriate to ask "What is RIGHT with Vulcan receivers?". They are generally shit.  Charles the Gunsmith.  

I have a AR vulcan lower that I used for a build.  Works great.  No function issues, but the finish is not that good.  Not that worried though.  I will be Duracoating it w/in 2 years.