1Poet,
No, a tight spot in the barrel isn't normal. Try this test. With a clean barrel, put a lightly oiled cleaning patch on the jag and push it all the way down to the breech. The patch should be tight enough to take a little effort in getting it down there. Now, start pulling the ramrod back out slowly. You will be able to feel if you hit a point where resistance increases. Mark the rod so you can reference it later.
There are two possible outcomes. First, you may not feel any "tight spot" in a clean bore. That's good. It means that what you are feeling is powder fouling that's accumulating in the bore after the first shot. We'll get back to that in a minute. If you do feel that tight spot there's probably is a problem with the bore. Chances are that it has chatter marks from the drill that bored it. As someone else mentioned, it could be pitting or rust. If you have the tools you can try polishing the bore. If you don't have tools just bring it with you the next time you come this way. I have a long rod and bore brushes in various sizes. I wrap steel wool around a brush, coat it with valve grinding compound, and attach the rod to my electric drill. Makes short work of polishing.
Now about that fouling. I've noticed that smoothbores sometimes seem to accumulate fouling out toward the muzzle. I have a completely unproven theory about this. We tend to think of powder and projectile as being separate things but in ballistics they can be lumped together as "ejecta". When the main charge ignites the expanding gasses push everything up the bore. The unburned powder is being propelled along behind the projectile. Of course, the amount of powder remaining decreases constantly and in a perfect world the last granules would burn just before the projectile leaves the bore. Powder burns most efficiently when under pressure. But what happens when the projectile exits before all the powder is burned? You get inefficient combustion resulting in more fouling at the point where the pressure dropped. There's your "tight spot". It's not the barrel, it's just crud. No big deal. Try increasing and decreasing the powder charge and see if the tight spot moves or disappears.
Here's something else to try. Don't lube the patches. What I do is wipe the bore between shots with a 7:1 mixture of water and Ballistol. The water evaporates leaving a thin coating of oil on the bore. The patch ball combination I use is loose enough that I can thumb start the ball and run it home with minimal effort. So instead of lubing the patch I'm actually lubing the bore. Try it and tell me what you think.
The variation in ignition time is harder to diagnose long distance. I noticed you said that you prick the vent before loading. Try making that the last thing you do before priming the pan. I also keep a rag handy and wipe the face of the frizzen, the pan, and the flint between shots. The idea that priming powder piling up beside the vent slows ignition has been proven false. So has the "too much priming slows ignition" belief. If you are curious I can direct you to the website of a guy who did testing using high-speed photography.
Take care and enjoy the rest of the weekend!
Storm