In Washington state, I have to pay WA state sales tax on a gun I have transfered into the state that I bought from a dealer or individual from out of state. That's around $45. Is this BS or what? How can they tax me when the transaction occured in a differnt state? I already bought the gun so how can they tax me afterwards? Anybody in WA have a work around for this? ATF is twisting FFL dealers to collect state tax or have their license revoked!

4% plus 20% if special ordered or 4% plus the fee for using the gunshops FFL

The dealer in your state is either a dumbshit or he's trying to rip you off.  It was purchased in another state - you owe either sales tax to the other state (collected by the dealer in the other state), or use tax to your state (filed and submitted by you, not the dealer in your state).  Either way, the dealer in you state has no business charging sales tax on the gun.  He can, however, charge sales tax on the cost of the transfer.  The service of performing the transfer of the gun to you may be taxable, so he can legitimately charge you tax on the amount he charges to do a transfer.

Did you send the funds out of state or through your dealer? If you used your dealer for the transfer of the money you probably owe sales tax through your dealer. If you sent the money direct you are supposed to pay the tax yourself. If your dealer insists on charging the tax if he didn't handle the money  nicely tell him you'll be sure to send a letter to the state tax office stating he collected the tax, noting the exact amount, so you won't be held responsible for the tax. If he is trying to jack you that will change his mind.

BS! But a nice piece of change for your dealer.

My dealer doesn't charge me on any tax for an FFL to FFL transfer. All I pay for is a transfer fee. If I buy from another state, I also do not pay their sales tax. I don't think you have to pay their sales tax since you are in a different state. But if you payed your dealer to purchase the gun for you, you do have to pay the tax.

This is a fairly big issue in Florida.  Anything ordered from out of state, i.e. mail order, internet, ect., by law is supposed to be subject to sales tax.  Problem is (for the state) it is at present unenforcable.  An individual is supposed to fill out and submit a form on such purchases, along with tax due.  I think I heard about 50 people do.  In a year.  Statewide.
The state is cracking down on business to business interstate sales, but individuals, all but about 50 of them, continue to buy out of state merchandise tax free.
Of course, I would never do such a thing.:-)

Having moved from CA recently I can attest, that you do not pay state sales tax on firearms purchased from another state, but you do pay USE TAX, which just happens to be the same percentage. I though my dealer there was ripping me off, so I called the State Board of Equalization and they clarified the issue. The dealer did not know why he had to charge tax, but only that he did. He did not know that it was actually Use Tax. Maybe something similar applies in Washington...