Yeah the storm was made in .45 for a while but dropped off. I wish there was a .45 ar
There are a few, but Olympic Arms owns the patents till (If I remember correctly) 2011 or so.
MGI Arms makes a .45 cal blowback AR that uses a modular lower receiver, and it uses Grease Gun mags. However it unfortunatly uses pretty much all Oly Arms parts.... There are specs for modifying a normal AR upper receiver to use the Oly style spring wire ejector, and after that, you'd need the barrel, bolt, and some sort of lower receiver or a receiver block.
A company called CNC Guns makes a 10% "paper weight" lower designed to use Grease Gun mags (its wider to accept them) that im sure a company here could finish to 100% spec and register it, if they imported them. They come complete with the magazine catch finished, but the magazine well not completely finished, and no fire control pocket or buffer tube hole made yet.
Also, there is the Cav Arms lower that can be equipped with an AR45 mag well block, as well as the Bazooka Bro's lower, and maybe a couple others...
There is also a company (I forget the name) working on a DI powered AR45 as well, using a rotating bolt head and the normal gas tube of an AR15. Supposedly it works quite well so far.