Semi-Autos

A couple of years ago Ryan and I discussed doing a tutorial on Glocks and turning them into accurate hunting guns. As I was working on the project I was made aware that Glock slightly frowned on some of the information I was providing. Things have changed a bit and I am going to proceed with the project with a few changes. I am going to do it in installments. That is all I can say right now. Some positive changes have made this possible. I have been getting a lot of questions about how or what I do to Glocks to make them shoot better. This post is not a comprehensive how to. Rather this is a post to give you an idea of what I am referring to. If you are not familiar with Glocks, metal work or general gunsmithing do not attempt to tackle these items discussed here. I will not attempt to teach the how, only the why. You can ruin a frame, barrel or slide easily. With that said here we go. Remove the magazine from the gun. Rack the slide 3 times checking the chamber to make sure it is empty. With the gun pointed in a safe direction, pull the trigger. Before you do anything to a Glock, break it in. I am talking about putting 150 to 200 shots through the gun. It may shoot good enough to satisfy you as is. If it does, great. If it doesn't, the most inexpensive thing you can do, that makes a real difference is order a slide lock from Carver Custom. Bobby discovered that the slide lock is instrumental in the barrel and slide locking up the same way every time. His are machined and are absolutely straight. This simple act will cut group sizes in half in some guns. Sure you can buy a cheap one that says machined off of eBay but that is hit and miss at best.

The gun on the bench today Fig 1 G20 10MM

Now the nitty gritty of Glocks that shoot 3” or better at 100 yards. 1 out of 100 might do it. Most obviously won't. The single biggest factor when it comes to building an accurate Glock is consistent lockup. Glocks are dependable. Why? Because they are built with what I call “slop” on purpose. When you run the barrel hood gap wide enough to allow a gun to cycle with a lot of crud it is impossible to make the gun lock in battery consistently. It's good enough and great for a duty or defense weapon but not for a precision hunting gun.

Fig 2

The barrel hood once fully in battery in the ejection port along with the position of the barrel lug in the recoil block forms your locked action. In order for this to be perfect several things have to happen. The first and foremost thing is the barrel hood being a perfect 90° to the bore center and perfectly square to the locking edge of the ejection port in the slide.

Fig 3. The way to determine this is with a precision square. I am not talking about a carpenter square. I am referring to a true precision square. The one I trust is a Starrett #20. No they aren't cheap but they are correct. See the pictures showing where to position the square on the barrel. There is a slight chamfer on the edge of the hood. The flat of the square needs to be positioned on the machined flat of the hood and the tenon pulled up to the locking edge and table of the barrel. The barrel shown in the pic is a KKM. It is also as good as it gets. The slide has to be checked the same way. I have never seen a Glock factory barrel that had to be touched. I am not saying I haven't had to work on a Glock slide. I am saying I haven't had to touch that area. If you ruin a slide this is probably where you will do it.

Next comes the slide barrel clearance gap. in order for the Gun to run there has to be a gap. Too much gap and the accuracy suffers. Too little and the reliability suffers. If we were talking a racing engine this measurement would equate to the ring gap. The way to measure this is to install the barrel with the slide off of the frame. Install the recoil spring so that it pushes the barrel to the rear of its travel in the port. Use a feeler gauge to check the gap. I am not going to get into the specific numbers, only the way to determine that number. The first blade that will insert completely in the gap to shelf is your gap.

Fig 4 and Fig 5

Next is making sure the frame is square with all guides on the same plane. Of course the slide is off the frame. Remove the trigger assembly and the recoil block. You need a perfect flat surface. Many of these are made from stone. There are metal machine tables that are built for the same purpose. Set the frame rails against the surface. There shouldn't be any rocking at all. If there is, it is generally one rail that is off. Remember a tripod will stand without rocking. A quad that is perfect will rock on an uneven surface. Since we know our test surface is correct we determine which guide rail is off and how much. Remember that with one guide high or low the frame will rock in two directions. With the frame rocked to the end of travel use a feeler gauge to determine how far off it is. Reverse the rocking to the end of the opposite travel and using your feeler gauge tale that measurement. If it's the same you have a high point. If it's not you have a low point. Since the thickness of the guide metal is the same most of the time a caliper measuring from the frame up will show a high guide. To prove this, remove the firing pin, extractor spring assembly, extractor and plunger from the slide. Slide the slide on the frame and it should travel freely. With the slide in the approximate position it would be in when in battery, use a caliper to measure the gap while holding slight downward pressure. Compare the numbers from the measurements without the slide on at each point. Any disparity will show up. Hint: most of the time it's the left rear that is off.

With all of that said this gun is as good as it gets. No wonder it shoots.

Fig 1

Fig 2

Fig 3

Fig 4

Fig 5