Honestly, I don't think you can "stretch" a magazine spring by just leaving it loaded for a few days. Chances are the magazine body has a few burrs or rough finish on it and using it smooths off the surfaces and makes it work better. Modern magazine springs aren't really affected by leaving them loaded, even fully, for long periods of time.
Actually in the case of loading a magazine you are compressing the spring. Not stretching it.
I didn't have any feed problems. But, I did have to load the original mag with 8-9 rounds for a couple of days before #10 would go in smoothly. As was mentioned it might be wise to check for any burrs or problems before heading to the range.
The mags I got last month directly from hi-point seemed precondition (all 10 in smooth as silk) and worked flawlessly. So you may be fine.
Got 2 extra mags the same day I got the 995ts, took all out the next day and shot 120 rounds and not a single mishap! been out several more times since then and still not problems, it has fired every round so far!
I'm a newbee too. I haven't owned or fired a gun since boy scout camp 22's.
I purchased a new 995TS with a spare magazine. After reading posts here, I decided to "break-in" my magazines before going to the pistol range. I loaded and unloaded the magazines by hand at least 6 times. I also bought a "speed loader" for the single stack magazine that had a fancy thumb lever that compressed the magazine spring to allow easier loading. The speed loader allowed me to compress the spring (you are not actually "stretching" the spring, but compressing it!) that helped to work the magazine action to smooth out burrs and rough edges from the manufacturing process. I did not oil the magazines but wiped the outside with a silicon-impregnated gun wipe cloth.
The loading and unloading by hand allowed me to get familiar with the ammo and magazine. I also read that the first round needs to be seated nose up and tight to the back of the magazine. I first loaded with 9 rounds and left them overnight. As the magazine worked in, it was easier to get 10 rounds into them. I left them loaded for a couple days.
I went to the range today and put 40 rounds through the 995TS. (I also shot a Ruger P-95 pistol.) Action from the magazines and through the carbine was smooth. Firing off-hand, I was able to hit the targets at 15 and 20 yards. No jams or problems. Reloading the magazines at the range was easy. I definitely recommend braking-in the magazines before using them at the range. I did the same with the pistol magazines and had zero problems with them.
The magazine that came with my (used) 4095 works flawlessly. The other day two new magazines arrived from Hi-Point and they wouldn't feed a single round. I loaded them both and stuck 'em in my closet, I'll see how they work next time I can go shooting in a week or two.
I too have loaded many a magazine for my C-9s (2) and my 995s (2), using both 8 round mags and 10 round mags. After a few sessions at the range and getting 'thumb palsy' loading mags, I finally broke down and bought a Uplula magazine loader. To get used to it, I unloaded 12 mags, then reloaded them. I immediately noticed, getting the last 1 or 2 rounds in the mag was no problem at all. I also noted a 'uniformity' in the stacking. While I have not had many FTF, I can't wonder if some were due to uneven stacking (even thumping the mags when loaded.) Any thoughts?
I ran 100 rounds through my 995TS today. A few mis-ejections was the extent of my problems. Maybe 3-4 out of the lot. Otherwise, happy trails are here, and extra mags are on the way to simplify reloading...