Hi,
Short answer is Yes it can be.
Short answer is No it cannot be.
Makes sense?? I didn't think it would, lolol.
95% of firearms and firearms related components are no longer under DDTC (ITAR) regulation; they have been moved to Dept of Commerce regulations.
Unless you setup an account with DoC along with AES (Automated Export System) and submit the required information you cannot legally ship that stock to the UK.
IF you do go through those setup processes and get the approval then yes you can ship that stock to the UK.
Sincerely,
Theis