FX barrels on other airguns?

I have a Hatsan Blitz and the accuracy is horrible, about 1meter/yard spread at 100meter/yards. I've seen many youtube videos and it seems it should be about 30cm/1foot spread at 100m/y.

I have no idea what's wrong with mine but I've been thinking about swapping barrels. I think buying a lothar walter barrel and installing it shouldn't be too hard but what about a FX barrel? FX uses a liner and housing system, how hard would it be to make it so you could install it on any other airgun?

Another thing I've been considering is buying smooth lothar walter barrels and then threaded sections with rifling inside it. This would basically create the smooth twist barrel where you could change 1 part to swap twist rate. Is this a good idea or would it not work because the engineering would have to be too precise for it to actually work?

Does anyone know how long the rifled section of the smooth twist is? 10cm/4inch? Shorter? Longer?