Gents,
I can usually find the answers to my questions by taking the time, doing the research, and asking he right people the right questions. I am having trouble with getting my answers, so I'm turning to you all to help me out.
It is my understanding that SBR ownership is now legal in my state of WA. I also understand that due to the way the law was drafted, and passed, I am not allowed to build my own SBR. The only way that I can legally own one, is to purchase a complete SBR from a dealer. So knowing these two facts I am trying to find the answers to the following questions.

1. If I purchase a SBR, AR15 platform, from my local dealer. Can I change the upper to another caliber if the lower is labled Multi Caliber? ie. Could I run a MK18 upper, swap it out for a .300 BLK upper? Both uppers with barrels less than 16".
2. Would I be constrained to the same barrel lenght as the MK18 upper? Could it be shorter or longer?
3. I realize that an AR that isn't classified as a SBR, the lower is the "Fireram". Is this true for an AR lower used in a SBR that is manufactured by manufacturers such as KAC, LWRC, or DD?
4. I have noticed a few auctions on Gun Broker that are AR15 SBR lowers, without an upper. They are on Form 3 and could be transfered to WA. But since I am prohibited from building my own SBR. Would purchasing one be considered building my own SBR?

Guys, If you can help me out on this, I would be very greatful. I suspect that If I want to have a MK18 clone, and a .300 BLK SBR, I will paying for a whole lot of tax stamps....

Thank you,
ST42

1 It doesn't have to be marked multi caliber.
2 Whatever length you want. It's only an SBR when the short barrel is installed or also in your immediate possession.
3 The lower is the firearm.
4 It's not an SBR if it doesn't have a barrel on it.

Nailed it.

Thanks guys!
Happy Thanksgiving to you all.
ST42

In WA State, your LGS won't be able to transfer a lower to you if you just buy one off GB that is listed as being on a forum 3.  It has to be a complete AR in order for them to transfer it to you.  They can build you one or you can buy all the parts and have them assemble it and then process it.

Thanks for the post! You have confirmed what I was told FTF the other day at Rainier Arms. Wish they had gotten that legislation correct the first time.

Can anyone recommend a dealer who stocks Colt SBR's? I'm about to start my MK18 quest, and would love to have it on a Colt lower.

They can't build you one it has to come from out of state.

Thats exactly what Rainier Arms said. In fact if you look on their website, you'll see a PDW that they build. They just can't sell it in WA..... Out of state only.

Correct!  

But they can assemble your parts for an SBR.  If they have an SBR it is my understanding that they can sell it to you, yes?

RA is no longer offering the F2/F4 service in which they would build/modify your AR into a SBR.  

If you are a WA resident, best bet is buy a factory built SBR on a Form 4.

I am not speaking for RA, but this is what I have learned in speaking to them about it.

Pantel Tactical in Renton was offering F2/F4 services.  Might contact them and see if they can do it.

http://www.panteltactical.com/

Thanks for the tip.