.this is my gun.with the ported barrel and compensator would i have to start in a higher class than i should as a beginner
No offense, but I surmise from your repeated posts that you seriously misunderstand what a USPSA match is, and what "class" and "division" mean.
I'm a USPSA CRO, and I'll try to take you through it one step at a time.
1. In a USPSA match, all the competitors shoot exactly the same targets, following the same rules, regardless of their "division" or "Class." Those only come into play at the end when adding up the scores. As I say, some are slow, some are fast, and some are half-fast, like me.

The idea is to hit the targets, not see how fast you can miss.
2. The "Division" is determined by the gun you shoot,
not by how well you shoot. Open Division and Production Division guns shoot the same targets in the same match, following the same match rules. Only their equipment differs.
3. Your
CLASS is determined solely by how well you shoot the classifiers, compared to all the other shooters
in a given division in all of USPSA. Until you join USPSA and shoot enough classifiers in a given division, you are
UNCLASSIFIED. All shooters start out unclassified.
When you shoot your first matches,
it really makes no difference what division you shoot in, because you're just learning and aren't going to win anything anyway. Basically you're just trying to get through it safely and not DQ. After shooting a few matches and seeing the different Division equipment and how the scoring works, then you can start to decide what division you want to shoot in, and perhaps buy some equipment.
So if you shoot your first match in
OPEN DIVISION because you have ports on your revolver,so what? You're just trying to learn the game, and your score is not going to be competitive anyway.
Your Sigma falls into Production Division, where it is more nearly like all the other division guns, but in most clubs you are going to get waxed by the more experienced shooters anyway. So what? Everybody had a first match, and most people wind up switching guns after shooting a year or so anyway. No hurry, you can eventually try all the divisions if your interest and budget allow.
No amount of detail I can type will give you the understanding you will get by just going and shooting a few matches. I understand your desire to have it all figured out and do great at your first match, but it just isn't going to happen. Most experienced shooters are very gracious and helpful to beginners, because they want other people to share the fun and become regular competitors. We assign a mentor to a first-time shooter to help him through his first match.
So, just go shoot a match. The first one will be a blur, but I guarantee you'll have a ball.
