Mag Extensions and Topping Off: Based or Busted? When it comes to concealed carry you either top off your magazine, meaning you load the chamber, then replace that round in the magazine for “x+1” capacity. You’re also going to use factory base plates, or you’re going to “upgrade” to aftermarket baseplates. In this article Erik from Nelson Gunsmithing and Mike of TacCat are going to dive into whether you should do either of these things with your defensive firearms.
Let’s clarify what topping off is for those that aren’t familiar, this is the process of loading a round into the chamber, and then inserting a full magazine. If your firearm’s flush fit capacity is 15 rounds, this turns it into a 15+1 gun. At full capacity you may have noticed that it takes additional force to fully seat the magazine; this is because the top round is pressing against the slide.
I’m personally not a fan of topping off. In my limited time at public ranges as well as watching a lot of YouTube University I see a lot of firearms, even with factory magazines, having failures to feed after the first round is fired. Occasionally the magazine will just fall out. Both of these failures are caused by the magazine not being fully seated. What happens is the individual tops off the magazine but then they fail to apply enough force to the mag as they insert it. From a concealed carry standpoint, a magazine not fully seated is a magazine on the floor at Starbucks. In other words, it’s a gigantic no-no.
Older guns don’t benefit from the years of engineering that go into modern magazine design. There is too much variation in magazine geometry and spring tension. This results in significant upwards pressure being applied to the underside of the slide under the breechface. That upward tension can create enough pressure to retard the motion of the slide and prevent proper cycling. While this issue isn’t as common with modern firearms, it’s one that I have an irrational fear of due to my experience with Murphy’s Law.
Best practice is to load the gun once and leave it loaded in the holster you intend to wear. Topping off adds a lot of administrative handling. Many firearms injuries involve distracted owners handling “unloaded” weapons. For new gun owners these tasks can be overly complex. Repeatedly chambering the same round can cause bullet setback, creating dangerous pressures as the bullet moves deeper into the case.
That said, the risks involved can be completely mitigated by careful and deliberate handling, combined with following the gun safety rules very diligently and training to correct malfunctions. There is a lot of fuddlore about the dangers of topping off. Modern advances in technology have eliminated most of these issues. You won’t damage your springs by leaving a magazine inserted and loaded for weeks or even years at a time, and you won’t break your magazine by slapping it firmly into place.
Base plates are items that increase the capacity of the firearm you’re carrying and can either come on factory magazines from the manufacturer, or you can purchase them aftermarket in order to increase the capacity of a factory magazine. These base plates can also add additional weight to the bottom of your magazine which makes them drop faster when empty. They also add additional length which makes them easier to grab if you need to strip the magazine from the gun.
I can be swayed either way on base plates. If they’re tested by the manufacturer and come with the firearm, or are sold by the manufacturer on a magazine I see absolutely zero issues. My issue comes with using aftermarket base plates specifically. A lot of people buy these extensions and they don’t upgrade the spring along with the baseplate, or they go with the cheapest option possible. Without additional power in the spring, you’re increasing your chances of having a failure to feed as the spring can’t push up round “x” into the chamber.
If you do upgrade the spring you run the risk of encountering a double feed because of the spring applying too much pressure to the next round. If you aren’t going to be able to perform testing on your potential upgraded baseplates/springs, I would say you should stick with factory base plates.
I used to do a little competition shooting, and baseplate extensions are very common among gamers. One of the advantages they offer is a significantly increased grip area. This makes the magazine much easier to grip and rip while doing malfunction drills. For guns like 1911s, designed with flush-fitting magazines, I would argue that extended bumpers like the Wilson Combat basepads are indispensable.
The discussion about capacity is less urgent. Capacity is a secondary concern to concealment, and bigger magazines are harder to hide. While there’s always a non-zero chance of a prolonged gunfight happening, the day-to-day risks of getting outed as a gun carrier are worth weighing carefully.
Of course our chief concern is always reliability. Off-brand magazines combined with cheap spring and follower kits are a leading cause of bad magazines, and especially in 1911s, magazines are overwhelmingly the cause of a lot of feeding issues. Use OEM mags supplied by the manufacturer. There is a reason Glock mags have such a proven record for reliability. If going aftermarket, use proven brands like Wilson Combat, Mec-Gar, and Magpul. Look at what gamers use; they test their gear harder than almost anyone else. They only use what works.
The decision is yours. You, at the individual level, have to decide which risks are worth taking if any exist, and go from there. You can only do this with rigorous testing and performance under constraints of time and pressure. No two guns are exactly alike and therefore no advice can be truly universal. Testing and maintaining gear is important, but the biggest foe you’ll face is user error. The only cure for that is time, training, and experience.
“Should I add base plates to my Glock 19? Or buy a Glock 17 magazine?”
Running an extended magazines has the benefit a tapered gripping point, making it easier to strip the magazine if it gets stuck. There is the additional length created by the magazine body itself as well as a lip or ridge from the OEM floorplate.
The other advantage is that extended magazines are built to factory specifications to work with the estimated number of rounds. They will provide relatively consistent feeding and pressure from the first to final round.
Magazine baseplates do not guarantee this because they are retrofitting an existing design. This is why a good set of extended baseplates can be so expensive. Anytime the baseplate is changed, the magazine spring must be swapped out as well. It’s always best to use OEM manufactured magazines but some companies do not offer extended mags for their firearms. In this situation, a new floorplate and spring is going to be your best option.
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In 1939 there was a Supreme Court Case called United States v. Miller. In this case regarding the National Firearms Act of 1934, the Supreme