For target shooting, and for the trick shooting I used to enjoy doing at my club and for demonstrations, I clean between every shot. You can get lots of opinions here about when to clean. I never could figure out when I needed to clean if I didn't clean after every shot. By the time getting a ball down was hard, It was also STUCK midway down the barrel!!! :shocked2: :rotf:
After having to pull those balls, and then clean, I decided that the Good Lord was having WAY TOO MUCH a sense of humor about letting me shoot a " dirty bore ", so I just decided to clean between shots, and avoid the situation entirely. And, you are correct: Consistency does require that you fire each shot from a bore that is similar in condition as it was for the prior shot(s).
If you used Hoppes #9 and that pumping system to clean the barrel before putting it away for storage the last time out, I would expect the flash channel to be clear, the nipple clean, and the bore spotless. Even that powder chamber should be clean. That is what that " Pressure wash " is suppose to do.
However, that is not what you are doing at the range.
Check for the existence, and diameter, and length of that Powder chamber. T/Cs have them; I suspect your GM breechplug has it too. This is the " NOCK-Style Patent" Breech. With a right angled flash channel leading from the bottom of the nipple, to the middle of the back of the smaller powder chamber. Most of the chamber run from 1/4" to about .32 caliber. Most are about 1/2" long.
As for what to do in a Gulf Area, where humidity is always high, I think you need to anticipate that condensation will increase as the barrel heats up. The more shots fired, the more moisture begins to condense on the flash channel, the powder channel, and the bore. What you HAVE been doing is cleaning the bore. If you don't have a reduced size swab, or brush to clean that powder chamber, moisture is collecting there, either from condensation, from TOO MUCH Hoppes solvent, or both. And, If your cleaning Jag is NOT the correct size to allow your cleaning patch to slide over the lands, only to bunch up when you pull the cleaning patch up, thereby digging down into the grooves, and pulling the crud out of the barrel from both the grooves and the lands, you will be pushing crud back down into that powder chamber.
Use a stepped cleaning jag. The most forward, or " bottom " ring, should be about .020" smaller than bore diameter. Each of the 3 or 4 other rings should be slightly smaller. You can put the jag into a hand drill or drill press and use a file to make such a jag. Some are also sold.
The important measure measurement is that it be small enough to pass the patching OVER the lands, so that the majority of the crud is not loosened until you pull the patch OUT.
The cleaning jag is different from a Loading Jag, for instance, used in loading a smoothbore barrel. There, you want a jag that has a forward edge that is just a few thousandths smaller than bore diameter, so that it will support and seat the edges of wads solidly against the sides of the barrel. You generally don't need this difference in jags seating either a PRB, or a conical in a rifled barrel, so one jag should do both jobs for you. Many shooters make the mistake of either using the same patches that they wrap around the ball as a cleaning patch(?), or they buy a jag that is too wide, and it won't allow the cleaning patch to slide over the lands. That then, pushes the crud down into the breech, and causes problems.
On humid days, have a small bottle of alcohol handy in your range box, and don't hesitate to flush out the barrel with it, if you find the " dry Patch" you run down to pull out the dampness from your " damp patch" is getting pretty wet. I use a second dry patch. By the time I have cleaned the crud out with my damp patch, 2 passes, one each side, or with 2 different patches, then run that first dry patch down, I have not had anything left in the grooves or on the lands that will hand up the second dry patch. If you don't have the time to flush with a 1/2 oz. of alcohol, then by all means, soak a cleaning patch, liberally, and run that down the barrel so that it does send alcohol down the powder chamber, into the flash channel. That is when I remove the clean out screw, BTW, and use a pipe cleaner to dry and remove the crud stirred loose by the alcohol. A wire down the nipple insures that it is clear. Do whipe off the nipple after each shot, and if you are seeing white powder collecting on the inside of that nipple, hit it with the hoppes, or a patch soaked in alcohol. Then check it to be sure the nipple hole is clear with your wire, after the alcohol has evaporated.
My brother lives in Florida, and we talk about his range sessions every time he comes back home.( 2x or more a week). I am aware of high humidity and high heat shooting problems. We talk about them all the time. What I am describing is what has worked for him there.
I have taken some of these suggestions to use myself here in Central Illinois during July and August, and in some Septembers when the Gods have forgotten that Fall is suppose to be beginning!!! We don't get the over 100 degree temperatures you do, but our relative humidity is rarely below 45%, and often higher than 70%. One day a couple of weeks ago, when Dallas was at 102, it was " only " 92 degrees here, but we had 72% relative humidity that gave us a heat index of 104!!! That is " muggy", by Cornbelt standards. And its hell on rifles with the condensation that is produced inside the barrels.
Conversely, in January through March, our relative humidity gets down to nose-bleed levels, often under 15%. Its the dry air and cold that now causes condensation in the barrels, more so when you take the gun indoors. Blowing down the barrel in below freezing temperatures turns the residue into soup! and fouls the powder charge every time. We clean with alcohol soaked patches in those conditions, and leave the water based Hoppes for indoor cleaning where its warmer. If you blow down the barrel outdoors to " loosen the residue" but then don't run a patch down before the barrel cools, the condensation freezes! Then you have to use alcohol, or de-icer or anti-freeze to clean the barrel! The colder it is, the faster you have to work, unless you just use alcohol and keep your breath away from that muzzle. Fall, and in some Spring days, is when shooting can be done in mild temperatures( 45 -65 degrees) and the humidity does not become a bother.