Yes, you can use 33-round magazines in 3 gun competitions.
There are a variety of different types of 3 gun competitions, each with different rules governing what kind and how many rounds of ammunition can be used.
Most matches will allow any type or capacity of the magazine as long as it follows the firearms divisions Rules.
If you’re competing in a match that has special divisions for pistol caliber carbines, your33 round magazine may give you an advantage over others who are limited to 10 or 15 rounds.
In some cases, reloading with larger capacity magazines may be faster than mag change time limits allowed, so it’s always best to check with the Match Director beforehand.
Robert Answered question September 2, 2022