A few questions about my No. 4 Mk1*

[smellie]

Buttstock should just be a bolt-on.

Remember, there is a Washer and Spring which have to be shifted over as well. See the factory exploded view of the rifle.

When swapping the Butt, be sure to remove the fore-end wood prior to swapping butts. Only takes a couple of minutes and prevents splitting your forestock.

As to your Weld, I must say that that is the ugliest one I have ever seen! DEFINITELY not Factory!