Be sure and check out your extractor. eGumpher's stickie on 738 reliability has a good piece on the extractor. It is for the 738, but I think it also has application to most of the external extractors, at least the Taurus ones.
Also check your brass. If the brass is scratched up, you may have a rough chamber that you can polish out with a Dremel and a felt bullet with some Jeweler's Rouge on it.
And since this is a new pistol, it could just be the magazines breaking in. Store them loaded between range trips to break in the springs.
200-300 rounds is considered a good goal for break in. Some pistols make break in well under that range, and a very few may go over but probably 90% will work out their initial issues within that range. Dry firing with snap caps can help the trigger break in, or smooth out, while helping you adjust to the trigger at the same time. I also take a piece of fine or very fine sandpaper and get rid of any flash inside the trigger guard as well as on the trigger, especially that little safety lever. Being the 709 is a carry piece, I would take off all the little edges anyway.
If you are wondering when you will know your pistol is broken in. It is broken in when it is operating the way you want and you have confidence it will operate that way the next time you fire it.