I agree with swapping out the barrel. Not only are the pins very tight but sometimes aligning them up with the holes of the replacement is difficult as well.
The pins were either slightly oversize on purpose or maybe even riveted into place with impact. They have to be that tight to stand up to pressures and stresses created by firing. Not only that, getting the flash hiders off the barrel can be a real chore as well. I have tried several methods to remove them successfully without damaging either and all I can say is that it takes time and patience.
One method that is OK but still not perfect is to remove the pins and apply heat to the large end of the protector. This will cause the protector to expand before the barrel and if you are quick enough, you can drift off the protector with a plastic/aluminum rod and hammer. Sometimes if you don't get it right, it will hang up. Stop right there. Quench in water and start all over again. This method will damage the finish where the heat is applied.
The metal in those flash hiders isn't hard. Brass or steel rods will damage them beyond acceptable repair. Do not use that hammer directly on the flash hider, either to take it off or pound it back on.
The other method that works well is to use a puller. When doing this, make up a brass or aluminum insert that fits part way into the muzzle of the barrel and fits snugly against the flange of the flash hider where it meets with the barrel.
When the barrel is being replaced on a No5 or any Lee Enfield action, the action wrench must be properly fitted. It has to be tight and not allow any movement at all. The metal used on these receivers is tough an only surface hard. They collapse or squash easily. Whoever changes it out for you, should have a proper action wrench, suited to this action.
