Rotating Your Carry Ammunition

(Source)

    I saw a good article at The Truth About Guns on rotating your carry ammunition, discussing the issue for both revolvers and semi-autos because they have somewhat unique issues and need to be treated slightly differently.

    The article begins, as you would expect, discussing the reasons why you want to regularly rotate or replace your carry ammunition: contamination of the powder or primer by oils or lubes, corrosion, or (if using a semi-auto) bullet setback being the main reasons. 

    Oils, as the article explain, can be drawn into a cartridge around the bullet or primer by capillary action and breakdown the powder and/or priming. You shouldn't have excess oil in the chamber or cylinder of a handgun anyway, but even minimal amounts over a long period of time can cause problems. The author relayed a story where ammunition carried (stored?) in a revolver over a number of years were duds which the author put down to contamination by oil. Frankly, it could just as likely been a matter of moisture from humidity: even if you don't live in a naturally humid part of the country, a carry piece is going to be exposed to excess humidity by virtue of it being carried in close proximity to your body.

    Corrosion can be another issue. Although the article doesn't delve into this much, I've seen ammo that has corroded over time. You might think that corrosion will mostly impact semi-auto firearms because it will interfere with the cycling of the firearm. But the cylinders of a revolver are machined to tight tolerances and so corroded ammunition may stick hindering extraction from the cylinder. In any event, corrosion will typically be the result of high humidity which takes us back to the first point raised above concerning contamination.

    The final issue discussed is bullet setback: i.e., that each time you empty and rechamber a cartridge into your carry gun, there will be some pressure on the bullet going into the chamber that will over some period of time push the bullet back into the casing potentially causing dangerous pressures if the round should ever be ignited. 

    The author gives some advice on how frequently to replace your carry ammunition. For revolvers, he recommends rotating them out every three to six months. For semi-autos he recommends that you "rotate out the round in the chamber every three to six months." But, he adds:

    For rounds in the magazine carried in the gun or spare magazines carried every day, rotate that ammunition annually or after about 12 months of carry. All of this rotated out ammo should find a home in a box or bag in your range bag.

    Test fire the rounds to ensure they fire and function. If they misfire, hangfire or have malfunction issues, investigate further to find and fix the causes. You may need to clean more often, or use (significantly) less lubrication after cleaning.

    The recommendation changes depending on who is writing the article. This article at Concealed Nation recommends once per year. This article at Police 1 recommends a carry rotation of 6 months to 1 year, which seems to be the standard advice. Winchester recommends a twice per year rotation for law enforcement officers using its duty ammunition, but for its civilian customers states: "While ammo is proven to last for decades if kept in controlled conditions, be on the safe side by refreshing the ammo in your concealed carry gun each year." An article at the Clinger Holster blog suggests every 6 months or less. And Mike V. at Everyday Carry Concealed suggests that "[a]ny round in the chamber should be rotated quarterly, while magazine ammo should be done at least annually. I also recommend you rotate ammo in your revolver quarterly, because of the increased exposure of the rounds." And  Luke McCoy at USA Carry recommends that the top round--the one repeatedly cycled through the gun--be replaced at least once per month while acknowledging that the ammunition that simply sits in the magazine could in theory last indefinitely. 

    Justin Carroll, writing at Lucky Gunner, has an excellent and detailed article on the subject and he writes:

    I reached out to several big-name ammunition manufacturers while conducting research for this article, and the only specific guidance I got was this: you should rotate your duty ammunition every six months. I think this is a great guideline, but it’s still only a guideline. If you handle your gun a lot and load/unload often, you should change your ammunition more often. If your gun is a pure home-defense tool that doesn’t get cycled that much and rarely leaves a climate-controlled environment, you can safely extend that number to a year or more.

    Even though I only own revolvers these days, I rotate my self-defense ammunition every 90 days. This is because I am inherently a “gun guy” and tinker with my gun a lot. I shoot it and dry practice often which means my guns get unloaded and reloaded frequently. My guns also get cleaned regularly which means my carry ammunition is in constant contact with oil, a notoriously effective primer-killer. Do you own assessment and consider your own use-case. And, when in doubt, inspect your ammunition and see if it’s time to change it out.

    With a revolver, the primary issue will be contamination from oils and/or moisture. Thus, you can probably err on the side of longer time periods before rotating the ammunition (although I think it should be a moot issue since you should be doing at least some practice with your carry ammo and might as well shoot up what was in your firearm when you do so). 

    The more serious problem, I believe, is with bullet setback in a semi-auto, which is mostly going to be related to how often you empty and rechamber each cartridge and the process for doing it. One thing you have to keep in mind is that setback is generally a slowly and then suddenly proposition, especially with the 9x19 as it uses a slightly tapering case. The reason is that as the bullet is pushed back, it will also loosen. So the same pressure that might only push the bullet back a 1/10,000 of an inch the first time, might push it back 1/1000 inch sometime later, and may eventually just push it completely loose and jam it back into and compress the powder in the casing. And you may not even be aware of that final catastrophic time since you can't see what happens to the bullet once it slides into the chamber. Is it safe? 

    So really, it isn't so much a question of how many months (unless you simply leave the cartridge in the chamber all of the time) but the number of times you are chambering a particular round. I don't have any hard data on this (i.e., I'm just pulling the number out of thin air, tempered a bit by my own observations over time) but I would be leery of cycling an individual cartridge more than 10 to 15 times, especially in the tilt-barrel Browning type of action where the bullet is more likely to be forced against the roof of the chamber when feeding. In my experience, this is a much more significant factor in inducing bullet setback than the bullet contacting the feed ramp. I don't have as much experience with fixed barrel systems, and none with rotating barrel systems, and it may be possible to go longer with such systems.