dd says no space left on device
 

I'm cloning a windows disk using gentoo;

On the old 66GB disk;
# dd if=/dev/sdb of=/root/winmbr.bin bs=512 count=1
# dd if=/dev/sdb1 bs=10M | gzip -v > winpartition.gz

Then after swapping in the new 500GB disk;

dd if=/root/winmbr.bin of=/dev/sdb bs=512 count=1
# gunzip -c winpartition.gz | dd of=/dev/sdb1 bs=10M
dd: writing `/dev/sdb1': No space left on device
0+306 records in
0+305 records out
10137600 bytes (10 MB) copied, 0.109885 s, 92.3 MB/s

# fdisk -l /dev/sdb

Disk /dev/sdb: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xe3f7e3f7

** Device Boot***** Start******** End***** Blocks** Id* System
/dev/sdb1** ****** 206848** 117207039*** 58500096*** 7* HPFS/NTFS/exFAT


Why is dd saying no space left after copying 10MB when sdb1 is 65GB?