Yes I have a 6724 flat top and I have the original B Square mount on it. It is a really good mount for a 1 inch scope. I believe stated in a thread here discussing this issue that B Square does not make a 30mm mount but I would check with them first because things always are changing. The mount I have allows me to switch between my day sight to my night sight with ease. The night sight has an Elcan mount on it. Some quick release Weaver type rings will work hooked directly to the top rail. I bought some Warne rings that were really nice. Actually they don't have to be quick release but that is a preference of mine. The ring option will afford a 30mm scope. Good luck!
Weaver rings work just fine on the AR-15 Flattop. Be sure to get the see-thru so you get the scope at a height that is comfortable. I have the B-Square one piece set up also, works OK. If you try the B-Square 1" riser block, you can use low rings and have a real good set-up with 1" or 30mm body scopes. The best set up I have come up with is Bushmaster's 1/2" riser blocks and med rings. Perfect height, looks clean, very adjustable for ring spacing and affordable. Don't lose too much brass
I've tried my two flat-top AR's with both med. and high rings alone and again with the ARMS #5 scope riser. I find this to be the most comfortable set-up personally (w/riser). It gives me a more natural head position to see through the scope without having to "hunker down". I use the Burris Signature Zee rings, they fit the rail on the AR just fine.
308 ... I tried the B-square on my Rock River Varmint AR and it worked OK. But, I changed to an ARMS 36EX Extended Swan Sleeve with Warne Rings for more flexibility with scope size, ring placement and eye relief. A friend has the Armalite one piece on his AR-50 and it works great. If you want the one piece mount, the B-Square is nice, but the Armalite is better. Another factor, the B-Sq is only available in 1" and the Armalite in 1" & 30mm. The ARMS Swan Sleeve and your favorite rings give even more options. Good luck ... Mike