Benjamin I gots dem Marauder magazine blues!

I have an almost new .25 Marauder. For the first few magazines, it fed just fine. Then, for some reason I can't remember, I thought I wanted to take the bolt out. I assumed that the ~1/2" diameter screw on top of the receiver would allow that, so I removed it, only to find that it's a ball detent that holds the bolt closed. So I replaced it.

Since then, the pellets just don't feed from the magazines. The bolt can only be pushed about 2/3 in before it locks up, at which point the magazine is stuck in place. It's like the bolt doesn't contact the pellet square on, or the magazine isn't indexed fully, so as to restrict pellet feeding.

Putting a .22 cal. rod in the barrel and tapping on it sometimes helps push the pellet back into the magazine to allow the mag to be removed. Sometimes that doesn't help and I have to force the mag out of the receiver.

Hand feeding works fine if I make sure to push the pellet in all the way. If I don't do that, the pellet cocks a bit when removing it.

What's going on? What am I doing wrong?

Is this a frequent problem? Help!
 
The detent should have no influence on how the pellet loads.
The factory mag I got with mine didn’t work very well. If I tried to load more than 6 the spring would come out of its keeper hole. You can see it on the back of the mag.
I bought two aftermarket mags which are perfect.

Sounds like the bolt functions without the mag, correct? I think you mag is not working correctly.
 
The detent should have no influence on how the pellet loads.
The factory mag I got with mine didn’t work very well. If I tried to load more than 6 the spring would come out of its keeper hole. You can see it on the back of the mag.
I bought two aftermarket mags which are perfect.

Sounds like the bolt functions without the mag, correct? I think you mag is not working correctly.
I suppose so. Very disappointing. I have ordered some aftermarket mags.
 
Here's what a pellet looks like after I try to chamber it. Note the crescent shaped cut on the top pellet. I'm assuming this comes from the rear end of the barrel.

Pellets.jpg