It's the LGS' reloads that are questionable. Using process of elimination you should have already concluded such.
- Stock, your gun fires and cycles factory new ammo without issue.
- With the upgraded quality parts, your gun fires and cycles factory new ammo without issue.
- With upgraded quality parts or OEM configuration, your gun fails to cycle whatever low quality reloads your LGS is trying foist upon their customers in order to make a buck.
Rule #1 about reloads: Unless you are purchasing commercially re-manufactured ammo from a licensed and well insured commercial ammo re-manufacturer, do not shoot it. Outside of commercially re-manufactured ammunition, the only reloads you should shoot are the rounds you've reloaded yourself.
Why?
Licensed, bonded, and insured commercially ammo re manufacturers are liable for the fitment of use of their end product. This in mind, commercial ammo re-manufacturers put in place the equipment, process, materials, and checks in place similar to factory new ammo manufacturers. Due to volume, they are able to acquire better materials at lower costs. Even with all of this, commercially re-manufactured ammo holds a higher probability of catastrophic failure than factory new ammo. Your saving grace should you experience catastrophic failure of a commercial re-manufactured round is the both the business size / presence and the liability insurance of the commercial ammo manufacturer.
Re-loads made by an individual and sold through a small gun shop or at a gun show hold an attractive price, but are a wholly unknown quantity. You have no idea what components have been used. You have no idea of the condition of the case used. You're putting your trust that some individual has put in the time and effort to check every case for fitment of use, has made sure that powder charges are of the proper weight, properly metered, consistent, and checked. This individual is an unknown quantity, not licensed, not insured, and lord knows if you can find them should something go wrong. They hold no vested interest in whether or not your firearm blows up or you get injured. They want the $$$ from your pocket.
When you reload your own, you have a vested interest in keeping your gun from blowing up and keeping your hands, eyes, face from physical injury. When I reload, I'm inspecting, cleaning, and re-inspecting every case. I know the components (primer, case, propellant, and projectile) used to make my own reloads. I put in my own checks along the reloading process.
Measuring the already proven bad LGS reloads with a caliper is not the solution. The solution: don't buy their bad reloads. Folks who haven't reloaded themselves do not truly understand the risk of shooting someone elses reloads. I highly suggest that you give reloading a try. Buy a Lee Hand Press kit and a 4-die set, calipers, and a reliable scale. Acquire a small amount of consumables. Acquire a reloading manual. Once you experience reloading your own rounds, you'll really understand.