Feeding issues don't always show up as a failure to feed and lock. While troubleshooting a rifle, I was manually feeding these .224 Valkyrie rounds and found that occasionally it would jam the bullet into the casing but it would still feed and lock. I noticed it because it didn't quite feel right, kind of like how you might notice a squib load, except this was just while dropping the bolt with the bolt catch. As hand loaders know, seating the bullet too deep can cause pressure spikes. I cant say if this would cause a catastrophic failure and dont care to find out, but minor changes in seating depth could lead to inconsistencies in accuracy or even be a cause of popped primers if its a repeating problem in otherwise quality ammo. Another subtle sign of rough feeding could show up as gouges or gashes in the bullet or brass. Use quality magazines and inspect feed ramps for burrs or snag points that could be catching the tips and edges of your rounds.

Single-use parts are single-use for a reason. A couple examples here are the knurled tip set screws used with lo-pro gas blocks and the locking block retaining pin from an FN 509T. While installing these parts might get you by for a while, you risk the chance of them failing you later on. The knurled tip screw is designed to bite into the barrel steel when its torqued to prevent it from backing out, but once you reverse the screw it rounds over the teeth and doesn't allow it to bite next time you use it. The locking block pin on the FN 509T has a larger section in the middle designed to keep it from drifting out. When the pin is removed, it rounds over the edges of the middle section and makes it easier for the pin to walk under use. . Don't use single-use parts more than once. If you think there's a chance you will need to remove that part in the future its probably a good idea to have a few spares. . We sell knurled set screws with competitive shipping rates on small parts on our website so feel free to grab a couple sets just in case. We also always replace the locking block pin and other single use parts when we work on guns that have them.

While visually checking alignment of a gas block with something like a rail is a great basic diagnostic step, its not always a guarantee of accuracy. Sometimes the port in the gas block can be undersized, drilled off-center, or in this case, both.

Couldn't have found a better guy to write on the subject. I know I learned a few things and you will too. Go check it out if you want to want to go full nerd on mags. . Link is in the bio

Quotas kill quality. As production volume increases, it becomes significantly more difficult to maintain a level of quality that you would at lower levels without the right systems in place. Unfortunately, the number of units delivered is often the only number that matters to many manufacturers and they expect a certain number, maybe 10-20% coming back for warranty. Meanwhile the end user has a 10-20% chance of receiving a part that is intentionally wrong. Its intentional because someone deemed it reasonable to allow unsatisfactory product into the market on the hopes you never notice. In this example, I have gas tubes all from the same place. The 3 on top came as they should. The two on the bottom have insufficient bends in them. While the exact location fore and aft isn't extremely important, the amount if offset is. I have found that more often, the bends in nitrided tubes are more likely to be relaxed and not have the required .156" offset. I dont know the exact cause of this but I expect it has something to do with heat from the nitriding process. I believe every tube should be checked for alignment after assembly, and many will need some minor adjustment. However, insufficient offset, especially on shorter tubes like carbine or pistol length in combination with a longer barrel nut can result in binding between the tube and the barrel nut and cause misalignment between the tube and gas key. Misalignment means premature wear at best and a gas key crashing into the tube at worst. Its your job while fitting and installing parts to look for inconsistencies or systems that don't operate as they should. Skilled assembly is ever more important the more we have panic buying or other high volume periods in the gun industry.