You cannot "slam" the charging handle forward.
To properly load the first round into the chamber: Make sure the carrier is locked to the rear and the charging handle is pushed forward until it is latched. Insert the mag, then pull on it to ensure the magazine is locked in. If the mag comes out, it's not locked in. If it's not locked insert and again pull. Do not slap the bottom of the mag. Slapping the mag can drive it too deep in the magwell and cause you problems. Then, simply hit the bolt release.
While you're at it, place a few drops of lube in the exhaust ports of the carrier. This is the most important point on an AR. Then, lube your trigger hammer assembly, especially the pivot points and sear engagement points
