I can't comment on the legal aspects, but after the ban he won't be able to haul it out to the desert and shoot it there. He would have to go to a gun range or private property, and not all gun ranges support 50 BMG.

You might want to see if he would have anyplace to shoot it . . .

Quoted: I can't comment on the legal aspects, but after the ban he won't be able to haul it out to the desert and shoot it there. He would have to go to a gun range or private property, and not all gun ranges support 50 BMG. You might want to see if he would have anyplace to shoot it . . .

Why not? Assault Weapon related laws regarding firing or something?

50 bmg is too loud for the 89 year old women at the range.

Quoted: I have a good friend I have known for 20 years since high school, he can't afford a .50 right now. There is no long gun registration here in NV, can I have him register the .50 in Cali so he could take it to Cali when he visits Vegas and wants to shoot it near home or am I missing something? I'm figuring in the eyes of the law the gun will be legally his but like I said I don't think he will throw 20 years down the drain trying to screw me out of a $3000 gun.

A long gun purchased in California goes through a "dros" form. Dros is, dealer record of sale. This dros form does not register a specific make or model or serial number to a buyer. It only determines if the buyer can lawfully own one and is not a prohibited individual. Hypothetically, he could have purchased the long gun years/months/weeks ago, but I still think you'll have to clear the hurdle as to how he "purchased" said longgun out of state without going through a dealer.
I *believe* the only way to get it to him and not have any problems is to have a California FFL do the transfer. Basically, you and him determined the price, if any, then ship your rifle to his local FFL dealer for transfer (I would get a "file" copy of the dealers FFL license so you would have a paper trail as to where your rifle went). He would then wait the State mandated 10 days before picking it up and filling out a yellow form.
If he's in or near Southern California Riverside County area, I use a dealer that charges $35 total and that includes the DROS fee. Let me know if you need his info or whatever.  

He is a Caliban resident, which is required for registering the .50, I think?  There are some places selling receivers between $300 and $600, to offset the costs.  Build later.