This is the lock on my fusil, the pan on a rifle will be a little smaller, but this method will still work. The COCK is what holds the flint shown to the left of the pan & vent hole. The HAMMER is what the flint strikes to create sparks. Shown here with a leather hammer cap on to the right of the pan.
The procedure is to load the gun first, before priming the pan. When you prime the pan it will be seen as above, the hammer back & the pan open. The cock set on half-cock. When the pan is primed, the hammer is pulled toward you to cover the pan. To fire you pull the cock back to full-cock, remove the hammer boot, point or take aim, & pull the trigger.
If the lock will not function because of a broken mainspring, then the cock will not spring forward when you pull the trigger. So to make the cock go forward toward the pan, you will have to pull the trigger & push the cock forward with your thumb.
Remove the flint from the cock & replace it with a piece of tinder, or a fuse made from cotton or linen material, or use some cordage made from coton or linen or plant material. This is your match or match cord, you now have a matchlock.
In practice it is better if you are using a smouldering match, to carry the match cord in your hand & push it into the jaws of the cock just before you are ready to fire. DO NOT load the gun or prime with a smouldering match in the cock!
When you are ready to give fire, push the match into the jaws of the cock at full cock, push the hammer back to open the pan. Take aim, pull the trigger, & push the cock forward so that the smouldering match end makes contact with the powder in the pan.
On a matchlock the part that holds the match is called a Serpentine, the cock on your firelock will be the Serpentine. This lock of course is shown the other way round, but you can still get the idea. The pan cover on your lock is the hammer.
Makeshift, but it will allow you to hunt in a survival situation. I have never broken any part of the lock on my fusil in 20 years. I did have the hammer refuse to spark one time, & I fixed it by heating it to cherry red in the camp fire & quenched it in my cold cup of coffee. Quenching the face of the hammer & then the rest. I did this so as not to make the hammer too hard at the angle. They have been known to break at that point if made too hard. Personally I would think it would take a pretty strong mainspring & hammer spring to break a hammer.
Here you can see what I carry in my knapsack. Ahammer spring on the top left, mainspring to the right. The mainspring clamp in the centre. Bottom left a wad punch, & on the right a spare hammer (the hammer got its name from an earlier model lock where the steel looked more like a hammer. It has been called a hammer or steel ever since. Not to be confused with the hammer on a percussion lock).
My turnscrew & screw I carry in my shot pouch. You need the turnscrew to replace the flint, and to replace lock parts & remove the barrel.
Doc: The CVA I think has a hooked breach so you don't need a turnscrew to remove the barrel except perhaps to push the barrel pin out.
This appears to be a Tinderlock.