Fixed measures are OK, but be sure you check them with an actual powder SCALE, to know just how close to the designated powder weight the fixed measure actually throws.
Most brass measures are 3/8" tubing, but some of the fixed measures are larger in diameter.
The 3/8" tubing is calibrated for FFg powder. If you use FFFg Goex, or any of the foreign made powders, the actual weight can be greater than the designation by the factory for the fixed measure. This is not much of a problem, until you start loading heavy charges. I have hand made my fixed powder measures from antlers, and I have used brass fixed measures made by manufacturers. As long as I have checked the measures with my powder scales I have had good service with fixed measures.
Oh, if you have a manufacturered fixed measure that is throwing powder on the heavy side, take a file to the top of the measure and file it down until it throw the amount you want it to throw. Its your measure. Just use a new, clean file on any brass tubing, and clean the file often, and when you finish using it on the brass measure. You may need to use a copper or bronze pick to get all the filings out of the teeth of your file.