Sighting-in a turkey gun can be a task at times, especially if you've chosen a new choke, new sights or new shotshells. Even if you're using the same shells and choke and sight you used last season, you should always sight-in your gun before the new season. The old saw of “anything that can happen will happen” certainly applies to our turkey guns.
I'm asked often enough about cleaning a turkey gun once it's sighted-in that I thought a few suggestions or guidelines might be appropriate.
Much of this applies if you have a receiver mounted sight of some kind. If you have open sights mounted on the rib of your barrel or just use the bead(s) for sights, removing and re-installing your barrel will have little if any effect on your point of impact.
First and foremost, prior to sighting-in your gun, I'd encourage you to “deep clean” the bore and the choke tube using the guidelines in the article “Cleaning a Shotgun Barrel” http://allaboutshooting.com/blogs/blog/tagged/cleaning-a-shotgun-barrel It's always the way to begin the process.
Once you've deep cleaned the bore and choke and have your shotgun sighted-in, I would not remove the barrel or the choke tube again during the season. You can change your point of impact, POI, by removing the barrel. Removing the choke and reinstalling it can also change your POI.
Since you've done all that range work sighting-in your gun, you don't want to undo that good work now just before the season.
I know that I've encouraged you to mark your barrel band, your magazine cap and your forend in some manner so that you can make sure that you have the same torque on the magazine cap each time you install it. That is still a very good idea and will put you back or very close to back where you were but unless there is some pressing reason to remove your barrel or choke tube after it's sighted-in and before the season, please...don't do it.
Since we're on the subject of installation, there's also a trick to installing/removing a choke that will help seat it the same way each time. Screw it in, back it out a turn and screw it back in. Do that each time and it is more likely to seat the same way. However, there's no need to take the chance once you're sighted-in.
Here's the method that I recommend to clean your bore and choke once you're sighted-in and ready for the season and I recommend this only if you really feel the need to clean your gun.
Open the action, make sure no rounds are in the chamber or magazine first. When you've done that, put the gun on its butt and put a piece of paper or a cotton patch in the action to catch debris from what you're about to do. I use a business card since it works very well.
Put a good brass/bronze brush of the appropriate size on a rod. Do not use any solvent or oil on the brush, keep it dry. Keep the rod away from the muzzle of the choke with your fingers or a guide and run it into the muzzle about 3" or 4" and withdraw quickly. That should produce a cloud of "dust". Do this several times and then run it all the way to through the the bore and through the chamber several times until the bore is free of visible debris.You may need to blow out any loose debris in the bore.
That's the same procedure I use in still target shooting. I do however deep clean the bore prior to sighting-in my guns but I never remove a choke or barrel after they are sighted-in.
Lastly, the one exception to the above “rule” may be if your shotgun is really soaked in a downpour. Moisture is the great enemy of our guns and rust can sometimes set-in pretty quickly.
When my guns get wet in the field, I try to dry them as quickly as possible when my hunt is over for the day. I will pull a barrel and choke, wipe them down, make sure they are clean and dry and do the same for the receiver and the rest of the gun. I'll apply any necessary lubrication and then reassemble and use those marks on the barrel band or stock and magazine cap, to make sure I'm back where I need to be.
Just to be sure, once everything is back together, I always shoot a few rounds to verify that the POI is correct.