I recently bought a spare Mossberg 590A1 and did the same mods to it as my other one. The problem being is that the magazine spring is now binding in the magazine tube and I can’t figure out why. After I chamber the first shell and fire it there is a second or two delay for the mag spring to push the next shell onto the lifter and most times there just isn’t enough strength to push it all the way onto the lifter.
Do you think its the magazine spring or possibly the follower? I did clean out the magazine tube after it happened and tried it again and it did the same thing.
edit The mods include a Vang Comp +1, plastic follower, and I believe a MD power spring. I haven’t had any problems with this setup on my other 590A1.
The factor spring binding is a common problem with the 590A1. Replace the spring with a higher quality one. Wolff universal 40" spring is a good one. Cut it to 28" and bend the ends down so they don’t stick up and you will be GTG.
The solid end nylon followers cause a loss of one round in the tube. If you want the full 8+1 cap use the cheap factory follower, if it works, or get a HQ metal follower. Vang makes a good one and it works well the 590. The spring fits into the hollow space of the metal follower and same amount of space in the tube is maintained. With a solid follower you lose about 1/2" of space because of the solid end. Also the spring end can get pushed out over the side and can cause it to hangup in the tube.