S&W Model 49 stuck side plate screw

If you want ,you can try a sodering iron for heat. Just put the tip on the screw head.
With a buggered up screw head you might be in for a tough battle.

If you know how , try and re-establish the grove in the screw head.

Think everything through before you act.

Apply Torque to the Screwdriver while tapping the top of the screwdrive with a plastic mallet. This sets up a vibration to loosen the screw. A third hand helps.

Sounds like you have fairly little experience with removing frozen screws.

I work on a fair number of older guns that need to be disassembled and cleaned before they are used and encountering stuck screws that may not have been turned in a hundred years is common. I prefer the lowtech way of doing the job. Give the screwhead a quick spray every day with a penetrating oil. WD-40 will work. After a few days put normal pressure on the screw. If normal pressure doesn't work, keep spraying it every day. I've had screws that took 2 months to move. If soaking the screw doesn't work, you're going to have to take it to a gunsmith. If you do take it to a gunsmith, make sure he has experience with removing stuck screws. Heat is risky. Avoid using heat if you can.

Heat from a soldering iron applied directly to the screw to break down any Loctite that may have been used. A screw jack is another approach. Whatever you do, have the frame well supported to minimize the risk of it slipping when you are torqueing on the screw. As someone else mentioned, shocking the screw while it is under tension often helps.

Find a screwdriver bit that fits the slot perfectly.

Then insert the bit in the slot and smack the bit with a small hammer a few times.

That will usually jar or stretch the threads enough to loosen it easily.

rc

If locktite used, it can take as much as 500 degree to break it loose.

Two (2) month to remove a screw? I hope you dont charge by the hour.

Use a small impact driver. H.F. $5-$6
Reshape the blade to fit closely. a little penetrating oil , and a firm hit will break it loose with no damage. Just make sure it's squarely and fimly in the screw.
God's gift to old motorcyles and guns.

plus 1, 1SOW on impact driver-get one that you can use Brownell magna tip bits
Kroil, kerosene - both good penetrating oils

Before you damage the screw head any more, try this.

If you have or can obtain use of a drill press, get stub screwdriver bit. Put the gun (less grips) on a pad on the drill press table where you (or a helper) can hold it tightly. Lock the bit into the chuck. Bring the drill press down and turn the chuck by hand to line up the bit with the screw slot. DO NOT TURN ON THE POWER.

Hold the chuck down with the press handle, and move the chuck back and forth by hand. By keeping the bit from jumping out of the slot, this will break loose all but the most stubborn screws.

Jim