jayarrG7, you are definitely on the right track with your thinking and question, it is important to make sure you have the right understanding of the configuration you are working with. And while "total weight" could be assumed to include all the motor guts, it is still a valid qstn to ask (to make double-darn sure) and a good reminder to manufacturers to be a bit more thorough in their definitions.
Calculating the stability characteristics can involve a few more subtleties too. I don't know how much of this you already know, but for the benefit of anyone else out there that needs to run through these procedures I am gonna go ahead and spell it out in baby steps--
Depending on how much flexibility you want to give yourself for flight, you build/analyze/ballast the vehicle to be safe under the worst-case “flight” configuration conditions. You want to identify the most-aft possible location of the cg, where it will be closest to the cp, and the longitudinal stability margin will be at its minimum.
What this usually means is you determine the required amount of ballast under conditions where you have installed the heaviest motor in the aft end AND you are using the lightest combination of components in the front end to determine the cg of your pre-ballast design. Forward items that will also affect cg position include minimum size of ejection charge, use (presence/absence) of batteries/circuit boards/cameras/payloads for nose e-bays, identification of the smallest (lightest) parachute anticipated for use (assuming the recovery gear is located in the nose), and use of the lightest variant of any other component located forward of the overall vehicle cg (such as alternate nose cones, removal of camera pods or fairings, etc). This “worst-case” configuration might never actually be flown but it will determine the amount of ballast required to ensure that the cg remains safely forward under all other (reasonable) vehicle configurations.
Weight of the heaviest motor should account for all parts of the motor that could remain onboard at the moment of ignition. These are the motor parts that will be flying, and as such they WILL influence the position of the longitudinal cg. If you want to split hairs, and give your vehicle design the absolute best possible cg analysis (and absolute minimum ballast weight) you could theoretically subtract the weight of propellant mass already consumed during the split-second that the vehicle is still sliding up the launcher, but then you would also want to account for exact weight (and detailed location) of paint and finishing materials, exact weight of actual ejection blanket/wadding/protection used, exact weight of e-bay batteries….go ahead, go crazy with it.
Crash repairs at the rear of the design such as added fin reinforcement (fiberglass wraps, fin-can foam, etc) should be accounted for as part of maximum aft weight. Ditto any design changes or “improvements” you make to a kit such as substituting stronger, heavier fin materials, or adding giant epoxy fillets all over the place.
You do the “worst-case” thing so you only have to do it once. You pay for the convenience of this by having to install (usually) an excessive amount of ballast weight, which then flies every time whether or not you really need it all. If you are just launching for fun and not striving at some cut-throat level for severe, extreme altitude, then a little extra ballast is no problem.
Another choice is to tailor the actual ballast weight to the specific configuration and vehicle load-out which you are about to fly, and to use variable ballast such as washers bolted to/in the nose cone. For this you would have to launch-prep the rocket, perform a field test to locate longitudinal balance (not always easy to do accurately in the field on a gusty day), and calculate the amount of required ballast weight. Or you could do a whole bunch of homework and prepare a “flight handbook” for yourself, with multiple tables of pre-calculated data accounting for all the possible variations in vehicle load-out and identifying the required ballast weight (hey, it’s what professional pilots use all the time!).
I kinda suspect you’re going to go with the extra ballast.
. back when I was building my patriot(1/4 scale l1 bird) I was wondering the same thing(motor weight)...I weighed my casing and all parts except the red cap for the nozzle and igniter...was all of 2 grams lighter than the weight listed in the catalog(I would guess that, the red cap is approx 2 grams. so use the loaded weight listed in the catalog. plus or minus 2 grams shouldn't make much difference in your rockets cg.
