The caliber, or the internal diameter of a firearm’s barrel, is measured in millimeters or hundredths of an inch. Just because a particular cartridge fits inside a firearm does not mean that it is the right choice. The wrong caliber can cause all sorts of problems for the gun user, and the firearm.
In a YouTube video, Matt of Demolition Ranch demonstrates what happens when he fires the wrong caliber bullet from a 9mm handgun, a .40 S&W handgun, and a Glock 23. You think he experiences some problems? You bet! Each firearm has a particular caliber requirement, and this experiment makes it clear why. In one case, he actually shoots the gun using a rope from a distance because he’s fearful for his safety. Let’s just say, matching the right caliber to the right firearm matters – a lot.
Problems With Using the Wrong Caliber
Firearm Won’t Load Correctly
In the video, Matt loads cartridges in the following pattern: correct caliber, incorrect caliber, correct caliber. When he fires the .380ACP caliber bullet from 9mm handgun, it does fire, but the next bullet does not load. The same thing happens with the .40 S&W handgun. The case of the wrong caliber round gets stuck in the barrel of the gun, preventing the next round from loading.
This experiment shows that while the wrong size caliber may indeed leave the barrel, it can derail the next round. This is clearly an issue when self-defense is at stake; it’s also going to hinder shooting practice and hunting efforts. Worse yet, if the wrong caliber projectile (or any projectile for that matter) is stuck in the barrel and another round is fired the results can be catastrophic.
Firearm Could Explode
In his book Do it Yourself Gun Repair: Gunsmithing at Home, Edward Matunas explains that using the correct caliber is a safety issue. Using the wrong caliber can burst a gun and injure the shooter and other bystanders. He reiterates the fact that a cartridge that fits does not necessarily make it the right one. Matunas writes “Assume nothing! When the slightest doubt exists, discuss the problem with someone well-versed in caliber identification.” He points out that in the case of older guns, the stamped/listed caliber may also have inaccuracy based on advancements since it was first released.
How to Find the Right Caliber
In cases where a firearm is new, the correct cartridge and caliber recommendations are found on the firearm. What about older guns or those that simply don’t have the caliber information listed? A knowledgeable gun professional can take the proper steps to determine the right caliber.
NOTE: These steps are ONLY intended for those with a vast knowledge of firearms; non-experts could damage their guns.
Slug the bore, using a soft 100% lead slug that is slightly larger than the barrel of the gun. Insert the soft lead slug in the muzzle and then either force it back out the muzzle or push entirely through the bore until it comes out of the breach. The slug is then inspected to determine bore/rifling condition, and in this case, measured to determine the caliber of the bore.
Create a chamber cast (in conjunction with the first step) with non-shrinking alloy that is melted and poured into the chamber of the gun. Once the alloy has cooled, it is removed and measured for accuracy.
The safest way to ensure you’re using the right caliber is to consult ammunition experts. Whether you’re shooting a handgun, rifle, or shotgun, the recommended caliber changes based on the make and model of the firearm. Be sure to protect yourself and your gun by using the proper caliber of ammunition.
Disclaimer: Always check with your state and local laws for restrictions before purchasing firearms or ammunition.