You won’t know unless you try it mate.
Give it a go and get it re leaded. 4 years isn’t bad going for not cleaning and still having good accuracy.
On a side not, if it takes say 50 pellets to re lead a barrel, why do you only get between 20-50 pellets in sample packs to see which is your guns preceded pellet. Surely you’d need to clean between different varieties and then use all the next variety to lead it up again, hence never really getting a true reflection of each pellet variety ???
Just a thought.
Back to the op. I’d give it a clean mate. It can’t hurt