one of the failures of the HL-Tiger is the position of the barrel.
What is wrong with the position?
I´ll show you.
If you take a look from above you will see, that the barrel is positioned centered to the mantlet.

If you take a look at the original, the position is a bit right of the mantlet center.
Including the notch at the mantlets edge.

The only way to correct this failure is to replace the barrel and the mantlet. To do so, try to get spares from a Tamiya Tiger or a Torro Tiger. You know, the one coming together with the Torro T-34.
To replace it is easy.
Follow next thread until the barrel is disassembled.
http://www.rctankwarfare.co.uk/forums/v ... 18&t=11483
Then replace the barrel (it should have the right length with the Tamiya and the Torro) and the inner plate.
Glue the back to it and follow the next steps at that thread to reassemble.
Greetings
Birger
For a lot more help with your Heng Long Tiger I tank, follow the below link ...
http://www.rctankwarfare.co.uk/forums/v ... 18&t=11459