Just depends how bad it is. Most of my custom ARs don’t lock up like “bank vaults”, nor do I want them to. I’ve gotten some of the oversized JP pins in the past to take out a little wiggle if it’s been more than I wanted. Tolerance stacking will lead to what you’re experiencing. Short of matched sets, that’s just how it goes. If they’re too tight, they can be fussy to break down. Grab some oversized pins (if you have gauges, just find out the best fit while still allowing you to push the pins out without a punch) and you’ll get a much better fit.
The Seekins combo, is there any wiggle at all once they are mated? If that’s what you are looking for, oversized JP pins may not quite get you there. If the Seekins combo is just a very slight wiggle when attempting to move the upper, then the JP pins will do what you want. My two sets of ADM uppers/lowers had a little more wobble than I liked, so I switched to JP pins, and now if I try to wobble the two, there’s very little play at all, but it’s not 100% perfect. All the receivers I’ve had that don’t have any play either have super tight pins, or are finicky to open/close since there’s no clearance.
Regular flat feeler gauges will work. The goal is the measure the gap between the upper and lower's pivot pin tangs.
I fit Accu shims to all my builds. I'm not a big fan of the plunger adjusters. The Accushim takes out all rock.
