Thread: SMLE no.1 Mk3* Magazine dropping out after firing a shot and a sticky bolt when warm

Or the rail that guides the bolt head might have crap on it, screw fouling the bolt - there are a number of reasons that could be happening. Extractor slot full of crap is another causing issues with the extractor being out of position, or issues with the internals of the bolt or where the cocking piece interacts with the rear of the action. Safety binding is another option...

A gunsmith will be able to confirm what's going on - it does seem unusual that the bolt tightens up in use though.