Welcome to Survivors parpat! :D
the first cartridge gets jammed against the
interior wall
Is the tip of the bullet hitting above the chamber or below?
Adjusting the feed lips accordingly may help.
Bending them slightly closer together will bring the tip of the bullet down, spreading them will bring it up. Just cycle the bolt by hand slowly and watch what it's doing.
Doesn't sound like it's off too far if only the first round does it.
You shouldn't have to "jam" anything. Just pull the bolt to the rear position and let it fly home under it's own power.
If you're holding the charging handle when it's going forward, don't.
Some rifles like different ammo. Some have been known to be "fussy" when using HP ammo.
HTH
Billy