I guess I will put in my 2 cents also. As everyone has stated, a 700BDL is out of your price range. I think you will be hard pressed to find a used one for under $400 that is in good shape. I believe someone else stated to get a really good scope and a lower priced rifle. I totally agree. For years I bought lower end scopes and then I finally bit the bullet and tried a Leupold. OMG! What a difference! I would really incourage you to get a rifle like a Savage or a used rifle in good condition and spend the money on your scope. You can find used rifles at GunsAmerica or GunBroker.com. Remember that you will have to factor in shipping, insurance and transfer fees on top of the purchase price. I know Savage has some combo deals and I also saw a Combo from Howa for around $500. The last thing to consider with your $500 maximum is ammo. You will have to buy several different brands of ammo to find which one shoots best from you rifle. You can easily spend another $100 doing this.
As far as calibers go, ammo for the good 'ol .270 can be found almost everywhere and is cheap. The .270 Weatherby is going to very expensive to feed camparitively speaking. The .270WSM is a newer cartridge but is gaining popularity. It outperforms the .270Win and is about even with the Weatherby. You can look at the 7mm's also. Only a slightly larger bullet but much better performance. You can buy heavier grain factory loads and it has better trajectory. The 7mmWSM doesn't really have a performance advantage over the 7mmRem Mag but it is a shorter case and should cycle faster for a follow up shot. A 7mm would be a better choice if you were giong after anything larger than a whitetail.

Try not to have tunnel vision for a 700BDL in .270Win. There are serveral different rifles in different cartridges that will perform very well. If your heart is set on the BDL, save your money this year until you can afford one. Don't skimp on the scope. You will only kick yourself later.