The standard answer:
Man up and push hard to lock it in!! (for use with properly loaded 30 rounders)
The follow up by someone who doesn't have a sense of humor and thinks the first replier is just being an idiot:
"Tac loads are easier when using standard magazines if you download to 29 or 28 rounds then the spring isn't as compressed and it's easier to load the fresh mag in since there's less spring resistance."
The next standard: You should buy the HK mags, you can fully load them and they're easier to seat in the magwell when fully loaded. Plus, they cost like 4 or 5 times as much as the USGI mags.
And don't forget:
Only wusses tac-reload. Shoot til dry, slap a new mag in and smack the bolt release. If Sam Stoner intended shooters to tac-reload all day long, he wouldn't have made the bolt release so damn easy to hit in sequence with loading in a fresh mag.
So, choose your favorite answer from the above, and just go with that.