What ammo are you using?
I have noticed that with different ammo I have seen different results. For myself I typically use 36 grain federal with no issues. If I use a larger grain I find on the first round sometimes it may not chamber. Another user said that it was necessary to push up on that first round other
wise it will jam and leave a smile on the bullet. So I tested it and found that to be true. If you search out the thread I think there might be pictures. If I come across it ill repost.
So my summation.
36 grain just load and go.
40 grain tilt the top bullet up in the magazine before loading and it should chamber just fine.
Good luck.