Don't have a torch?.... heat some water until you first see the bubble & pour slowly down the bore with the muzzle upwards using a funnel. When the water reaches the top of of the muzzle -- stop & let it soak for an hour.

Dump that water out - repeat this procedure -- except this time, only let the barrel sit five minutes -- until it gets nice& hot. Having a hammer,socket & socket wrench right next to you, dump the water & moderately tap the wrench handle with the hammer in a loosening direction inside a vise.

Some folks find success emerging the entire barrel in a filled bathtub overnight. I do not recommend that procedure -- small gaps underneath the open sights could get contaminated with water& form rust eventually.