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Lock Back or Not?

By Bob Londrigan, First Published in Front Sight Magazine, July 2005

Why do I set up my competition guns to not lock back after the last round? Since I often hear that question, I thought I would go over the pros and cons of having a gun lock or not lock back. Then I’ll explain the best way to make this type of modification to your gun.

The stock 1911 is designed so that the slide locks open after the last round in the magazine has been fired. This happens because the slide stop engages a pad on the magazine follower that pushes the slidestop up into a detent in the slide. Most 1911 users view this as a desirable feature because you can chamber another round and be ready to go just by inserting another magazine and releasing the slide stop. However, when competing with 2011 style guns there are some disadvantages to this system – enough so that I prefer to disable this feature in the competition guns I build.

The magazine setup that I prefer uses a Grams follower. This follower (as are most other aftermarket followers) is designed to sit up as high in the magazine as possible in order to maximize magazine capacity. Increased capacity is good, but a side effect is that a high-positioned follower may cause the slide to lock back prematurely with one round left in the magazine. This can be adjusted out but it can be a tedious and unreliable process. If the slide is set to not lock back, then this problem is avoided and you can still benefit from maximum capacity.

Reloading the gun while the slide is locked back with your adrenaline pumping in the middle of a stage can have some disastrous results. In 2011 style guns, you can actually over insert the magazine when the slide is locked back. This jams the magazine in the gun. Realize that you are pushing a wedge shaped object (the magazine) into a hole (the magwell) that is narrow at the top.

As a result, it may wedge itself in and then be hard to remove. Over inserting the magazine can also break the tip off your ejector if you have an extra long ejector that hangs over the magazine well. The top of the magazine will contact the ejector because it no longer has the bottom of the slide to stop it. Thus, it pushes up on the ejector sometimes with enough force to snap it off.

The best way to set up your magazine to not lock back is to modify both the slide stop and the follower. To begin, drill a small detent in the slide stop to engage the slide stop plunger. This keeps the slide stop from moving up or out in the event it is bumped by the nose of a bullet. Use an extra long drill or a dremel tool with a small carbide ball bit to make the detent. Then modify the ledge on the slide stop as shown in Figure 1 (the slide stop on the left has been modified). You want to trim it flat but leave enough material so it won’t break. Be sure not to take off any of the height.

If you modify only the slide stop, the tab on the follower may still jam on the slide stop causing magazines to stick or you gun to malfunction. Therefore, you also need to modify the ledge on the follower. I like to trim the ledge down at a 45-degree angle as shown in Figure 2. This keeps the follower out of the way of the slide stop and keeps it from binding.

After you have modified your slide stop and follower, test fire the magazine to see if the slide locks back or if anything binds. It should not. If it does, check your follower and take a little more off the ledge.

On the flip side of the issue, competitors have various reasons for wanting to set up their gun to lock back. For example, you might want this to shoot limited 10 or IDPA. In this case, you have two choices: You can either switch back to stock followers, or you can modify your after-market followers to ensure consistent last round lock back. Since the lock-back ledge on stock followers usually sits a little lower, they generally work fine with a slide that locks back early. You can switch to a factory follower if you are shooting limited 10 or IDPA because maximum round count is not a priority.

To modify your aftermarket followers to ensure you gun does not lock back occasionally with one round left in the magazine try the following solution: First, put a detent in the slide stop. This will help prevent the slide stop from engaging and will often solve the problem. If it does not, then you are going to have to either modify the pawl on the slide stop or modify each of the after-market followers. Work on the slide stop pawl first to raise it a little. Take material off the bottom (raise the engagement surface). This may solve the problem with most of the followers. If it does not, then work on each of the offending followers. One word of caution before you start working on the followers - make sure the lips on the magazines are tuned to the proper dimensions. Opening or closing the dimension on the lips affects how high the follower sits and, thus, affects the lockback. Begin by modifying the ledge as shown in figure 3.

I like to use a dremel tool with a 5/16 cylinder bit to take down the ledge. Take off just a little at a time and then test it. With three rounds in your magazine, shoot the gun until it is empty. If necessary, take a little more off the ledge and then test again. Repeat as needed until you get it right, and then repeat it a few more times to make sure lock back is consistent. When you have one follower working properly, copy the setup on any other mags that don’t work

To lock back or not to lock back is a personal choice based on your shooting style and preferences. Whichever way you choose, the important thing is that your gun does the same thing every time. Only then can you depend on it in a match.


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