I assume you have removed the spring , cleaned and lubricated it as well as the inside of the magazine.....Having said that, gentle polishing of the feed ramp BY HAND, not Dremel, should be fine. However, I am in 100% agreement with replacing/checking the magazine spring first. I doubt ball ammo should be giving you much of a problem....hollowpoints might, but I wouldn't polish unless you have to do so. I had the exact same issue with my Nighthawk Custom government size 1911. Only one magazine kept hanging up when I dropped the slide, constantly just one of the Italian made ACT magazines that came with the gun (exact same magazine as the Novak), all the others worked fine. Another reason why you should always number your magazines and track their performance. After checking the magazine's feed lips and confirming they were OK, I replaced the spring with a Wolff plus 10 lb extra power spring and all is right again. I only carry Wilson ETM magazines these days which have not given me a single FTF or FTE in about a year now. I cycle four of them at the range and carry two of them...all four have work flawlessly for one year, with many rounds through each. But the ACT I keep exclusively for range work and always track which magazine might give me an issue. If the spring doesn't fix the problem, then it could be the feed lips as they sometimes crack or bend (obviously check these first). For example, the ACT mags are notorious for that problem and the reason Nighthawk no longer use them.
You can also try switching magazine springs with one of the magazines that isn't giving you a problem and then observe whether or not the problem goes away with the bad magazine. If it does, you will probably start having issues with the other magazine, which certainly would confirm a spring issue. Either way, the Wolff plus 10 extra power magazine springs are a sound and inexpensive investment, as are their recoil springs which you should change every 2,000 rounds in a government size 5" 1911.....17 or 18 lb springs work well for me. If you shoot mostly 45 ACP then 17 lb is fine, if you shoot a lot of +P ammo then an 18 lb recoil spring is a good way to go. No one makes a better gun spring than Wolff.
If after addressing the magazine spring you are still having problems, dump the magazine. I would do the magazine spring fix first and then if the problem still occurs, just remove that magazine from the equation by tossing it in the trash and move on. Once all problematic issues with the magazines are removed then if the problem still exists then it may be time to consider alternatives like feed ramp polishing, but personally that would be my last resort. I would probably want the manufacturer to address the issue under warranty as if you mess up the gun you have just negated your warranty. Remember 1911 feed issues are almost always magazine related in nature...look there first before modifying the gun itself.
As far as ammo, I've always had good luck with Blazer Brass and Winchester White Box ball ammo from WalMart....about $29 for 100 rounds and very good practice ammo. The Blazer Brass I find is somewhat cleaner than the Winchester but isn't always available. I use CorBon 230 gr JHP for carry though, but may be trying some of the new Hornady Critical Defense round, especially for winter carry where heavy clothing could pose an issue with JHP.
Here's the link to Wolff springs.......good luck and let us know how you make out.
http://www.gunsprings.com/1ndex.html