Hi Colin,
I have a spare 54mm liner that I will never use if you want to purchase? I believe it has never been used.
I do not use Iron in my barrels, just Aluminium and plating, this has turned out to be very reliable and in terms of cost for wear rate, probably cheaper than using iron liners.
Problems revolve around initial costs (very high) and getting quality liner material in a form you can use. A small amount of knowledge is needed for the fit of the liner but other than that it is trouble free.
Iron Liner available now, email me if interested.
If you want to know more of the alloy, email me if interested!
Cheers,
Alan