At first glance, they seem like a great bargain. But there are a few issues that you need to consider. You are building a quality product and doing your own gunsmithing. One rule in gunsmithing is to NEVER do shoddy work. Everything you do should be well planned and to the highest precision possible. You are building an expensive part for your weapon (but cheaper than buying a commercial one). Take pride in your work and build it the way a professional gunsmith would.
Issues with preformed plugs.
- Very hard to get a perfectly centered hole drilled on a tapered surface
If you drill into the cone female side of the plug, the drill bit tip will not contact the center because of the angle and the sides of the drill bit will start the hole. This is very Imprecise and will result in a hole off center. If you flip the plug over and try to drill from the pointed side of the plug, without a fixture to hold the plug perfectly centered, you will be starting your drill bit more or less by trial and error.
- The plugs are too large to fit into the tube without pounding or forcing
Others say to "pound" them into your tube and let the tube size them. Try it. You will never get them back out after using without destroying either the tube or the plugs.
- The plugs my not be perfectly concentric after drilling
Some say to use a 3/16 bolt, a couple washers and a nut to hold the plug into a drill press for sizing. They obviously have never built a quality suppressor or they would know that is a bad idea. It has to be tight for starters. How do you get a bolt tight on a tapered surface without deforming it? How accurate is it? It is just not a great idea. The patented Jform tool holds the formed and drilled plug perfectly aligned so you can put it in a drill press and use a file or sandpaper to size it for a nice push fit into your tube. That is what you want, not a loose fit or a "forced" fit. You are trying to be accurate like a commercial suppressor is.
After sizing using the JForm tool, your plug will be perfectly concentric with the precision center hole.
A great video on how to use the tool with a comparison test firing at the very end. https://www.youtube.com/watch?v=_5elo8qkmVE&feature=youtu.be
Drill bit geometry explained
Drill point geometry explained in detail