Hi Martina, you're a little early with your request as even with "home resort" owners can only book 11 months ahead of arrival date.
You have a number of options,
1) You can hope a BCV owner has the points available and will book the room for you in June/July. IMHO you're limiting your chances with this option.
2) You can wait until October time (7 months window) and hope that owners of any of the DVC resorts have the points available. I don't think May is that busy a time although BCV is probably the most popular of the DVC resorts due to it's smaller # of rooms and the cache of the SAB pool. Obviously you do have a risk that there is "no room at the Inn"

, but I think you'd have plenty of time to make alternate arrangements.
3) If you find an owner of another DVC resort that has the points available, you could let them book their home resort in June ( so you are certain you have some accommodation booked) and ask them to try to transfer the booking in October to the resort you are after. Again you run the risk that there is no room at BCV available, but at least you'd know you did have some top quality accommodation booked even if it wasn't your first choice.
IMHO 300 odd points is quite a lot for any one member to have lurking about, you may have more luck if you're prepared to split the deal and take say 180 from one owner and 120 from another. I think those sizes of points are more likely to come up than 310 in one bash. Again another option for you, depending on how adventurous you are, would be to take two different resorts, say OKW (cheapest for points) from Tuesday to Sunday (5 nights) would be, I think, 156 points and 4 nights at BCV (Sunday to check out Thursday ) would be 112 points. That would save you $400 or so on your accommodation AND give you the chance to check out two DVC resorts. There is no real advantage, IMHO, of the location of BCV when using the waterparks,MK,AK or DTD so you could use OKW for park visits to those areas and BCV for MGM, Epcot and maximum use of the wonderful pool of SAB. This would also give you the option of getting a LOS pass for the OKW leg of the stay and visiting ALL the themeparks in those days and using the stay at BCV purely as pool days.