I took a look at the TMLRA firing line and I didn't see a single benchrest shooter using premeasured charges. A lot of them use adjustable powder measures and are very methodical about using them. With practice, you can throw very repeatable charges.
A few use crank type powder measures used for reloading smokeless powder.
This is one of the most popular powder measures in use. It has a spring loaded valve and you push your adjustable powder holder into it to fill it.
Where you see premeasured powder charges used is in NSSA skirmish shoots. These shooters shoot and reload on the clock and having a bunch of premeasured charges ready to go makes for faster shooting, and is historically more accurate than loading from a powder flask in Civil War re-enactments.