Not the bolt. The little "button" that is to the right of the charging handle.
Several things could cause lack of lock-up.
* incorrect head space
* incorrect cartridge shoulders or overall length
* the bolt binding inside the carrier and not twisting lugs into lock-up
* crud in the chamber
* chamber slightly out of spec
* Mag not sitting quite right causing drag on the bolt carrier or mag follower tilt, or cartridges dragging/tilting as they move upward inside the mag.
Def look into the easy things like a dirty bolt and carrier, mag drag, try different ammo, dirty chamber.
Grab the bolt carrier and see if the bolt rotates back and forth smoothly inside the carrier. Look for high abrasion spots. Pull the firing pin back and forth and check for smoothness. Remember its gotta do all this a couple times a second when its running good.
Take the upper off the lower and turn the upper upside down, then slide the bolt carrier and bolt into the chamber several times and see if the lugs are getting hung up inside the chamber. And, take the bolt out of the carrier and drop into the chamber and see if its a nice fit and see if it twists into lock up.
Your issue sounds fixable for sure, especially since a nudge on the forward assist gets it into lock up.
