Moving Files in SQL as Blob (Filestream)

Question

I have setup both of my Servers with Filestream for T-SQL access (and my DBs). I created tables on both Servers:

CREATE TABLE mytable(
[UI] UNIQUEIDENTIFIER ROWGUIDCOL NOT NULL UNIQUE DEFAULT (newid()),
      [Data]      [varbinary](max)FILESTREAM NULL)

I am inserting my File (.bak File, Backup of my DB 5,2GB) as:

INSERT table ( Data )
SELECT * FROM OPENROWSET (BULK 'F:\myDB.bak', SINGLE_BLOB) AS X

I insert it on a same table over Linked Server in my 2nd Server. Then i want to create my .bak file again:

DECLARE @fPath varchar(400) = 'F:\myDB.bak' 
, @init int,
@data varbinary(max)

SELECT @data = (Select data from mytable)

EXEC sp_OACreate 'ADODB.Stream', @init OUTPUT; -- An instace created
  EXEC sp_OASetProperty @init, 'Type', 1;   
  EXEC sp_OAMethod @init, 'Open'; -- Calling a method 
  EXEC sp_OAMethod @init, 'Write', NULL, @data; -- Calling a method 
  EXEC sp_OAMethod @init, 'SaveToFile', NULL, @fPath, 2; -- Calling a method 
  EXEC sp_OAMethod @init, 'Close'; -- Calling a method 
  EXEC sp_OADestroy @init; -- Closed the resources 

But my File only comes out as 1,6GB. and after trying to restore it i get:

Msg 3013, Level 16, State 1, Line 9 RESTORE DATABASE is terminating abnormally. Msg 3287, Level 16, State 1, Line 9 The file ID 1 on device 'F:\myDB.BAK' is incorrectly formed and can not be read.

What am I doing wrong?