The spring tension will loosen up over time with use the more times the mag is loaded and unloaded. It's quite common for new G30/G30SF mags (10-rnd and 9-rnd) to be a chore to load to capacity and load in the pistol. If you aren't comfortable slapping the loaded mag in hard, load the mag with the slide locked open for a time or download the mag by one round (9 total) until it loosens up.
After struggling with the first new, 9-rnd Glock mag I bought for my G30SF, I thoroughly researched what others had written about problems with mags and corrective actions to solve them. As new information became available, I recorded it all in one post over a period of several months. I settled on a maintenance and troubleshooting procedure that has worked well for me with all my CCW mags (9, 10, and 13 rnds). There could be something in the post that may help you. See this link: http://www.glocktalk.com/forums/show...93&postcount=2