A does-what-it-says-in-the-tin offering that's exactly what you think it is and is precisely as awful as you fear it'll be: cynical trash sniggering over its "adult" (as in rude) content like a 12-year-old with a copy of Razzle. I'm not averse to screen nudity - as the old line goes, "if it's essential to the plot", and there's certainly a place for it in art and entertainment. But in the best of them - Basic Instinct, Dressed To Kill - there's more to the film than just the nipple count and the thrusting bums. Well, this is not the best of them. This isn't even Basic Instinct 2. Nor is it much of a faux-grindhouse movie: it's more of a mean-spirited morass of sex and violence in the manner of Bitch Slap and Hell Ride; sweaty, ugly lowlifes ruthlessly abusing the meek and innocent. To which the only "adult" (as in mature) response is "grow up".
The principal nude nun in Nude Nuns With Big Guns (and I don't discount the possibility of a thudding pun related to Big 'Uns) is Sister Sarah, sucked into the drugs industry by the Mother Superior and various high-ups in the local Catholic Church: turned into a junkie prostitute at a strip club-cum-brothel, she vows revenge and sets about exterminating the priests and bishops involved (one of whom appears to be attempting the vocal inflections of Christopher Walken for no particularly good reason). In panic, the Church call upon the Los Muertos biker gang, a gathering of phenomenally repulsive individuals operating out of a gas station in the desert....
This is rubbish. And it's not even entertaining in an undemanding Friday night tits-and-gore rental kind of a way. For all the nudity and lesbian couplings, for all the gunfire, rape and sleaze, it's actually pretty dull and tiresome. If you must make wannabe-grindhouse garbage movies, there's no rule that says they can't have some level of quality in them. Like Machete or Hobo With A Shotgun, something that might make an amusing spoof trailer doesn't necessarily translate to a feature-length film (Machete kind of got away with it; Hobo empathically didn't.)
And again: if you want to watch naked women, then buy some porn. This is porn for people who don't really want to watch porn, so they watch this kind of thing because it's a proper film with a proper story and proper characters and there are a few bits where they've got their clothes on. Absolutely not worth the time and money, or indeed the effort expended in pressing the Play button.