For those like me, every time you start to think you know a thing or two about guns, you learn something new that makes you realize how little you know and how much there is to learn. Bullet setback was one of those for me. I was talking with my brother about it just a few days ago and I blew his mind. He definitely knows a thing or two about guns, but didn’t realize how serious bullet setback could be. So I decided that writing a detailed explanation could do some good for a lot of people. Here we go.
What is bullet setback and why is it important to know? Bullet setback is a condition where the bullet in a gun is forced further back into the cartridge by repeatedly being chambered. The bullet is stripped off the top of the magazine and forced up the feed ramp and into the barrel. Hitting the feed ramp pushes the bullet into the cartridge. This can cause overpressure and reliability problems in that ammunition.
Wow, that’s a lot of information in a tiny explanation. We are going to go into even more detail and cover a few more things in the next few sections.
Detailed Explanation of Bullet Setback
Bullet setback is a condition that occurs in some guns, and is little known by many shooters. It usually only occurs with concealed carry ammunition and duty ammunition (referred to from here on as carry ammo). It can happen with any ammo, but usually only occurs in carry ammo because it isn’t shot that much. It tends to be much more expensive than practice ammo, which disqualifies most shooters from shooting it often. Instead, they buy it because it is more effective self-defense ammo. They don’t shoot it, but instead, load and unload it often over time.
The real problem is with guns that have a feed ramp to chamber a round. In a typical series of events, a round is stripped off a magazine, and while being fed toward the barrel, hits a feed ramp. By hitting the feed ramp, the round experiences resistance. It overcomes that resistance, but not unscathed. The bullet inside the cartridge takes the brunt of the impact and gets pushed back into the cartridge a little bit.
Tiny amounts of bullet setback (after being chambered once or twice) aren’t a big deal, but it can become problematic if it happens over and over again. Modern ammunition is built to be very durable but it isn’t meant to last forever. Its primary purpose it to be shot; secondary is everything else. Problems and dangerous situations can start to occur if bullet setback happens and nothing is done about it.
Why bullet setback is dangerous
First and foremost, bullet setback can be dangerous. Each firearm is designed for a specific cartridge that has a maximum amount of pressure that can occur within the chamber and remain safe. When bullet setback occurs pressures are increased (most of the time only by tiny amounts). If the bullet is set back enough, the pressure can become so great that the gun can have a catastrophic malfunction—and even explode.
Not every caliber is created equally and not all amounts of bullet setback are equally dangerous. Obviously, it is all dangerous to some degree, but the dangers of some calibers is compounded. It is best to change out ammo if bullet setback has occurred. That way, you can avoid the dangerous situations and avoid other problems we’ll talk about now.
Voided Warranty
When using carry ammo some warranties only cover the ammo if it has been chambered only one time. If you chamber a round, unload the gun and chamber it again, the warranty on the ammo is void. This may bother some people more than others, but it is worth noting.
Other problems caused by bullet setback
Malfunctions
One of the problems caused by bullet setback is that it can cause malfunctions to happen. As the bullet is pushed further back, it can also cant one direction or the other. Then the shooter usually unchambers the bullet and chambers it again—or chambers another round. Then the round that has bullet setback is now in the magazine. If the ammo is shot, that round is going to be fed into the gun and it is now 1) shorter and 2) canted. If that round is in an awkward position it may not load. And carry ammo is usually loaded in guns that we absolutely need to work when the trigger is pulled.
Walking out
Another problem that can happen either to the chambered round or other rounds in the magazine is that the bullets can walk their way out of the casing partly or completely. This isn’t necessarily a cause of the bullet setback, but it can be. If the crimp on the bullet has already been loosened by the constant chambering, it may have an easier time walking its way out and causing some sort of malfunction.
Even the rounds in the magazine that have no bullet setback occur can still experience the bullet walking out. They are in the magazine and are experiencing all the activities of daily carry. They are banding around against the magazine and against themselves. If left in the magazine and the chamber for too long, the bullets can loosen up and cause problems.
Rim destruction—kinda
Okay, okay, this has nothing to do with bullet setback. But it does occur the same way and usually at the same time. By chambering the same round many times, the rim can wear down. This is caused by the extractor constantly engaging the rim and yanking the round out of the gun. If the rim has been worn down too much, the round won’t extract and a malfunction will occur. Like previously mentioned, this would be the worst case scenario for a carry gun.
Which types of guns can cause bullet setback?
Not all guns cause bullet setback. It usually only occurs in guns that 1) use a feed ramp to load another round (semi-autos) and 2) are used for self defense/fighting.
Feed ramps are what provide resistance to the round when it is on its way to the chamber. The round is stripped off the magazine and continues flat—with little resistance—until it reaches the feed ramp. The bullet impacts the feed ramp, causing the setback, and then ascends its vertical path to the chamber. So really it’s the slide pulling the round upward on the feed ramp that causes this problem.
The other “type” of guns that cause bullet setback are guns that not only have the feed ramp and slide, but also are used for self defense or fighting. These guns specifically use special ammo that is set aside for only fighting purposes. All practicing is done with cheaper ammo that is shot constantly through the guns. This ammo is usually removed in order to shoot practice ammo and reloaded after practicing is done. This process of unloading and reloading triggers the bullet to constantly engage the feed ramp and experience setback.
So bullet setback is likely to occur mostly in handguns, but other guns can experience it too. AR-15’s for example are often used as home defense weapons. While rounds aren’t usually chambered nearly as much as rounds in carry handguns, setback can happen in those rounds. Loading the rounds in a magazine and dropping the bolt carrier group home drags the round up the feed ramp and into the chamber. Doing this too many times could cause the round to set back.
How to avoid bullet setback
Bullet setback is bound to happen at some point if carry ammo is kept for long periods of time. It’s out in the elements and many things can’t be avoided. But to ensure that you keep your firearms safe from its effects, there are a few ways to at least slow it down.
Switch it out occasionally
The most obvious way to avoid bullet setback is to change out your carry ammo occasionally. We have the absolute best article about switching out carry ammo titled “Switching Out Carry Ammo: Answers From Manufacturers”. In it we discuss 9 different carry ammo manufacturers and their recommendations on switching out their ammo.
After our own experience with guns, talking to manufacturers and consulting gun experts online, we have determined that carry ammo should generally be switched out every 6-12 months to avoid bullet setback—and other dangerous conditions the ammo can experience. Depending on the specific conditions, ammo might need to be switched out much more often than 6 months. Conversely, if conditions are more favorable, the ammo can be kept longer than 12 months.
Regardless of how often you choose to switch out your carry ammo, the fact remains that it should be switched out occasionally. The best practice would be to shoot the ammo through the gun when you are ready to switch it out (making sure there isn’t serious setback in those rounds). After that ammo is shot through the gun, load new carry ammo in it.
Chamber round by hand
Another awesome way to slow the effects of the ammo degrading over time—and to hopefully avoid bullet setback completely—is to avoid the feed ramp altogether. Instead, of loading the rounds into a magazine and dropping slide home, lock the slide open and place the first round into the chamber by hand. Then the slide can be sent home and the magazine can be inserted. The weapon is then ready just as it would have been otherwise.
Following this process instead of the process most people follow gets the weapon ready without dealing with bullet setback. That doesn’t mean the rounds will last forever and they don’t need to be changed out; but it can help prolong the life of the ammo. Without bullet setback you will just have to determine how long you think the ammo will last with all the other effects still degrading it over time.
Don’t unload the gun
A very simple way to avoid bullet setback is to resist unloading your carry gun. If setback occurs by chambering a round (unless the previous suggestion was followed), then unloading and reloading a gun often can cause it to occur much more rapidly.
Obviously, there are reasons guns need to be unloaded. If you’re going shooting at the range, the ammo needs to be unloaded and placed aside in order to shoot range ammo. The other reason to unload your gun is if you can’t ensure the gun is safe while not on your body. For example, most people unload their guns everyday as soon as they arrive at home. Though this isn’t necessarily essential, they do it anyway.
If your gun needs to be unloaded for safety’s sake, then unload it. It isn’t worth sacrificing safety to save a little on carry ammo; however, if you can avoid unloading your firearm as much as possible, it can prolong the life of your ammo significantly.
Rotate chambered round
Yet another way to avoid bullet setback is to rotate the round you put in the chamber whenever you unload your gun. Obviously, as we mentioned already, avoiding unloading your gun is best, but sometimes it needs to be unloaded. When you do, place the round that was just in the chamber at the bottom of the magazine. That way each round will only be chambered so many times and it will occur evenly. Most people don’t keep track which round they chambered last and end up chambering the same round over and over again. It will also keep the rim of the case from being destroyed from too many extractions.
Obviously, this strategy can be used by itself to reduce the effects of bullet setback (and wearing down the rimes of the casings) but combining it with any of the others can further prolong the life of the ammo you carry.
Best Practices when bullet setback occurs
The answer to this question is tricky. Technically, when bullet setback occurs, the ammo should be destroyed. But the answer isn’t as simple as that. It really all depends on the cartridge and the gun. If the bullet is set back on an extremely small amount, then it’s probably okay to shoot. If it is set back significantly enough that it is clearly shorter than your other cartridges of the same type, then it probably shouldn’t be shot.
The real question enters with how much is enough setback that it is no longer safe to shoot? And there is no clear answer to this; there is no line that determines when it is safe to shoot and when it isn’t. That’s why changing out your ammo occasionally—as well as implementing some of these other strategies can help. You won’t have much bullet setback if you’re taking the precautions we’ve discussed already. But to be on the safe side if you can see the setback without having to really look at the ammo, it’s probably best not to shoot it. If you can’t even tell that it’s setback until you pull out your caliper to measure the thousandths of an inch of setback, it’s probably okay to shoot.
Related Questions
What is the longest I can carry ammo without replacing it? As long as ammo is kept in peak condition it can last indefinitely. Most manufacturers recommend switching out your carry ammo every 6-12 months, but it can last much longer than that depending on what conditions it has been subjected to. Keeping it too long without inspecting it can cause problems with proper function and safety; but a simple inspection can expose these potential problems.
What is the best kind of carry ammo? There are many factors to explore when evaluating carry ammunition, but here is a list of the most common concealed carry ammo:
- Hornady Critical Defence/Hornady Critical Duty
- Speer Gold Dot
- Federal HST
- Underwood Xtreme Defender
- Winchester PDX Defender