Yep, now that's a heavy BB. Good job!
Btw, you can calculate the weight pretty accurately if you can tell what size the rail is. For example, if it's 130lb rail (which is a pretty common size here in NA), then 3ft of it will weigh approximately 130 lbs. That would be 303lbs for a 7ft length. I believe the largest rail in NA is 155lb rail, so the most it can weigh is 361lbs.
Usually the rail size is pressed in the side of it, but you may not have enough of a rail section that shows it somewhere. Or, you can look up the rail profiles (I think they are online somewhere, maybe A.A.R has them) and make some close measurements and tell what size rail it is.