One of the best ways to buy a firearm for personal use is to buy one that was previously owned. Don't laugh. Most of the handguns I purchased when I was in my twenties and thirties were pre-owned, and they are still putting rounds down range.
Generally speaking most used firearms are in good shape. Many have actually rarely or even never been fired. Firearms tend to be impulse purchases by people looking for protection, and they aren't likely to take said weapon to the range.
When shopping for a used gun, the first thing you need to do is define the mission of said gun. Will this be a duty weapon, are you collecting the weapon, or are you going to rebuild it into a full custom piece.
Condition of the Gun
Used handguns are often more worn than used long guns. Therefore, it's a good idea to establish criteria for judging them before you go shopping.
I classify used handguns in several categories: worthy of rebuild, beater or what we call a "truck gun" here in western Pennsylvania, and last is a gun that's near mint or cared for so well that it's suitable for daily carry or for use as an off-duty firearm.
Generally, it's not a good idea to carry a used gun on duty, but let's discuss that more in a minute. For now, let's look at the categories.
Worthy of Rebuild: If you think a gun is worth a complete rebuild, here's what you want to look for before you commit to the project.
If the piece you are considering for a rebuild is a semi-auto handgun, make sure that the frame and slide fit well, that the slide and frame rails aren't cracked, and that there is no peening of the frame to slide. You also want to check the safeties and confirm that they function and that all the parts move freely. You don't have to check the springs and the other parts because they will be replaced during your custom rebuild.
A gun that you are considering for a custom rebuild does not have to be perfect. What you are looking for is a solid foundation for your work. And remember, the finish can look rough if there is no pitting. You're going to refinish this piece anyway, and the rougher the gun looks, the better chance you have of buying a real jewel for a bargain price.
The Beater: The finish on a beater can be rough as long as it is not pitted or rusty. Pitted and rusty guns have been abused and you want no part of them.
You're not buying a beater gun for its looks. So all of your criteria for judging this used gun should favor function over form.
Make sure that all of the safeties function properly. Of course, the number and type of safeties vary from gun to gun, but here's some basic things to check where applicable.
The thumb safety and decocking lever are easy to test; simply apply them and see if they work.
Checking the firing pin safety takes a bit more effort and requires taking the weapon apart. After asking the seller if it's OK to disassemble the weapon, do so.
Now push the firing pin into the slide. It should not protrude into the chamber/hood area of the slide. If it does, the firing pin safety is not working; find another gun. If it appears to work properly, find the firing pin safety plunger and depress it, then push the firing pin in. Now release the plunger; the firing pin should stay in place. When you depress it the pin should be released; this is a good test of the firing pin safety.
If the firing pin is not retained by the safety plunger, it's likely worn out or maybe just filled with crud. Have the seller take the safety apart so you can take a look. If it's filled with crud, try cleaning it. If the parts are worn out or broken, either pass it by or ask the seller to reduce the price to cover the cost of parts. Remember, parts for older guns can be very expensive, so keep this in mind as you decide whether to make the purchase.
Next, inspect the frame and slide. Make sure that the rails aren't cracked, dinged, or otherwise damaged. The slide should travel smoothly on the frame without binding, and check for peening of the slide and frame. Peening is usually caused by a weak recoil spring, loads of shooting or shooting hot +P rounds, poor maintenance, or any combination of the above. Be wary of a pistol with this kind of damage, even if it's just a beater.
OK, time to move on to the barrel. From my experience selling used guns, it seems the first thing most folks want to do is press down on the hood of the barrel. In the days of old 1911s this was a good test to see if the barrel link/pin fit well. But on most modern firearms this will serve little or no purpose; nor will trying to wiggle the muzzle of the barrel in the slide. If you work it hard enough the barrel will move. The barrel has to have some play to function properly.
After checking for barrel fit, remove the barrel. You are checking the locking lugs of the barrel and the throat of the barrel. Look down the barrel to see what shape the lands and grooves are in. Unless this is a polygonal barrel like a Glock, they will be barely pronounced. You also want to feel down the barrel to make sure there are no bulges; bulges are a sign that the pistol was shot with an obstruction. If you feel one, move on. A bulge in the barrel is very bad; it's potentially deadly should you decide to shoot the gun.
While the barrel is out of the slide, check the slide's interior. Look at the firing pin area. If it is smooth and concentric, this means the firing pin functions properly. If the firing pin area is nasty looking and not dirty, it could be that the owner was running hot home reloads and there was primer flow. This could lead to other unseen issues with the pistol. Pass it up.
One other thing you want to check while the pistol is disassembled is the inside of the frame. You want it to be in good shape with no cracks. Most of the time you will see very little wear on the inside of the frame; maybe some scratches from dirt, but that's about it. The feed ramp should not be dinged up, as it shouldn't get damaged from normal use. The finish on the feed ramp may wear off, but it shouldn't be chipped.
Beretta and Taurus semi-autos present a unique concern: the locking block. Make sure it is not cracked, that the plunger slides smoothly, and that it exhibits no signs of damage. This part is known to take a beating when the gun fires +P ammo. However, damage to the locking block is not a dealbreaker. It is not expensive and it's easily replaced.
The last thing to look at is the sights. Pretty much, just make sure they are in the proper position. You don't want them pushed off to one side or dinged up and damaged. If the sights are beat up, be wary. It's really tough to damage a handgun's sights unless you drop it or worse. This is especially critical on Beretta 92/96s and the Taurus 99/100 series. On these guns, the sight is part of the slide and not easily replaced.
Buying a used firearm for duty or off-duty carry can present liability issues. If you have an accidental discharge or shoot someone in the line of duty, you will have to answer some very probing questions about the gun. Was the trigger worked on? Was the safety tinkered with to make it easier to use? You get the drift.
There is one class of used firearm that is suitable for carry on duty: the factory rebuilt handgun. A number of companies that make duty weapons sell factory rebuilt weapons.
These pistols are agency trade-ins that are sent back to the factory and are returned to original specifications. Such pistols are a good deal and will save you significantly over buying new in-the-box models.
Agencies also trade in their used firearms at dealers and you can find some bargains in these collections. You can also find absolute junk.
However, if a reputable dealer or wholesaler is selling these weapons, they are generally serviceable. Almost always these pistols have been examined for frame cracks and have sights and safeties. Beyond that, it's buyer beware because the dealers give them just a cursory going over.
When I worked for a major outdoor retailer, we would buy agency trade-ins from a local wholesaler. The evaluation process entailed going through cases of pistols and searching for the nice-looking ones. After that we went back through the pile of nice-looking pistols to see if they functioned properly. You can do this, too. If you are dealing with a wholesaler, ask to see other pistols and pick out the cream of the crop.
Check the frame for cracks, check the barrel for fit, and then test the slide to make sure it functions smoothly. On agency trade-ins it's also particularly important to check the sights. Most agency trade-ins have night sights; see that they still "glow" in the dark. If not, ask the seller to deduct the cost of the sights from his price.
Used Wheel Guns
Used revolvers can make great backup guns or personal weapons. And while they are not as prone to wearing out as semi-autos, there are still some things that you need to check before you hand over your money.
Make sure that when you cock the hammer or stroke the trigger through double action that the cartridge chambers line up with the barrel. Also check the following: Does the cylinder lock up when you cock the hammer? Does the cylinder rotate out of the frame when you push/pull the cylinder lock latch? If the answer to any of these is no, pass unless you can make the repairs or the shop will do them for you and appropriately price the revolver.
The next thing to check is the forcing cone area of the barrel. This area takes a beating from the flash when each cartridge is fired. If there is erosion, which will look like severe pitting, I'd pass because chances are the revolver has been shot hard and shot a lot.
While you are checking the forcing cone, examine the frame. You don't want the pistol if the frame is cracked or damaged. High-pressure loads can do this and unless you look inside the cylinder area of the revolver you might not see it.
Another area to check on a revolver is the barrel. Most revolver barrels are threaded and screwed onto the frame; so make sure the barrel is snug and doesn't move. I have seen barrels that can be twisted and tightened onto the frame. Believe me, you don't want them. When the barrel is snug on the frame, the front sight better be centered on the frame, not off at the one o'clock or eleven o'clock position.
Ask for a Warranty
Some dealers of used firearms offer warranties. Unless you are planning on rebuilding the gun, ask for one.
No matter how well you check the pistol over in the store, you will want to be able to return it if the first time you take it to the range there are major issues. Issues that become obvious on the range but are almost impossible to spot in the store include: magazines not functioning, slides that don't go into battery, and sights that fall off.
Also, when you give the gun a thorough cleaning, you may discover that the frame and/or slide is cracked in such a way that you couldn't see it in the store.
In the case of a revolver, you might find that the forcing cone and or cartridge chamber is slightly out of time, which will shave bullets. You'll feel this if it happens.
If a shop doesn't offer a warranty, I'd pass on buying a used firearm there. You are spending hard-earned money on a tool you may need to save your life, and you want to be satisfied with its operation and confident in its performance.