December 12, 2012

Manufacturing an In-Shop Shooting Drum

Here’s an item you can make in your shop that will make your life easier and your work better.

In the course of a typical day’s gunsmithing, I test fire at least three weapons for such things as inconsistent primer ignition, failure to feed properly, and sear disengagement. With the cost of commercial bullet traps somewhere in the stratosphere, I had no choice but to make my own to keep costs down. My indoor trap, which I use for pistols and rimfire rifles, cost less than $25 to build. Even if you use brand new materials, it should cost less than $100.

First, I found the right person in the sheriff’s office and talked to him about my gunsmithing, never mentioning the intended bullet trap. All I wanted to do was make a contact, let him know that I did gunsmithing, and make sure that he would remember me when I contacted him later. I invited him out to my shop, although I was almost certain he was too busy to do it within working hours, and would be in too much of a hurry to get home after eight hours on duty.

Then I started building my trap—one which I fully intended for my own test use and seldom to be used by anyone else. This turned out to be the right decision; one of the few times I let someone else use it (an experienced law-enforcement officer), he shot a hole in my floor. I carefully rethought my policy and also reinforced the drum.

Manufacturing an In-Shop Shooting Drum

Courtesy, American Gunsmith

An exploded view of the shooting drum and the components involved.

I started with the energy, momentum, and blast of the most powerful shell I would be using in the drum and figured how much lead would be required to stop a bullet from the largest caliber that I would allow in the drum. I multiplied that by 10 and considered this to be a sufficient safety margin. Under the lead, I used a steel plate which would be sufficient to stop a bullet by itself. This figure was for approximately 1/4 inch of 10XX series steel for the bottom and schedule 40 on the vertical cylinder.

My design, the essence of simplicity, has worked better than I had hoped. I did make some upgrades from my original design. The upgrades included a muffin fan to disperse the smoke which remains in the drum and can give you a fierce headache. I also added a large note which admonishes me to open the windows for good ventilation. The trap is so quiet that none of my neighbors even realize that I pop off a few rounds each day. I do warn my wife before I shoot, as she is more comfortable knowing that the “pop” she hears is intentional.

I started with a 12-inch-diameter, thick-walled steel tube, 2 feet in length, and welded my bottom disk onto one end. If welding isn’t available to you, the bottom disk should be cut 1/2 inch smaller in diameter than the inside diameter of the outer can. Next, I lined the sides of a 30-inch garbage can with convoluted polyfoam, turning the bumpy side inward and gluing the smooth side to the inside of the can. The trash can I chose, only because it was handy, was a relatively thin-walled indoor wastebasket of the tapered 20-gallon variety. The strength of this can is immaterial; it is just to support the sound-deadening foam and the top seal.

The top plate was made of 3/4-inch plywood cut about 1/2 inch larger in diameter than the top of the trash can. Into this, I cut a keyhole with a saber saw, rounding the edges on both sides and the top perimeter with a router. The keyhole is big enough to accommodate the largest handgun without risking bumping into the wood. On the underside, I stapled some split-foam water pipe insulation with the split at the bottom to capture the top rim of the trash can. The sleeving I bought had a scribed line along it to aid in cutting without spiraling around the tubing. Don’t let the words “trash can” spook you. Steel and lead will be doing the containing of the fired round.

Into the top plate I cut a hole for a muffin fan—easily found at any electronic supply house—and the holes for a protective plate for the fan. I cut the steel protection for the fan about 6 inches square, and drilled each corner for mounting screws. The fan was mounted on the underside of the wooden top plate, and the 1/4-inch steel plate was mounted on 11/2-inch standoff tubing. The usual muffin fan is about 1 inch thick so this gives about 1/2-inch clearance for the fan. That proved to be plenty. I then lined the underside of the wooden top with the same bumpy foam. Next time, I might choose to make the keyhole larger in order to edge it with the same water pipe insulation as the outer edge. While this isn’t really necessary, it would look better.

The whole unit was placed on a roll-around dolly I made for the rig. I next added tire weights. The steel cylinder was placed into the trash can and centered so the clearance area around the cylinder could be filled with tire weights, if so desired. In the absence of welding the bottom plate, center the thick bottom plate inside the trash can, and lower the steel cylinder onto it, being careful to center it, also. Add tire weights around the outside of the cylinder up to about 3 inches deep, then fill the inside to about 12 inches. This will hold the cylinder centered on the bottom plate. I’ve found the inner cylinder and the foam inside the trash can to be sufficient to satisfy both my wife and the deputy sheriff I had inspect it later. After picking up damaged brass for too long, when I get around to it I am going to make a brass-catching basket around the area in which the gun is held, and about 8 inches down. In the meantime, I just have to limit the number of shots I fire before I pick brass out of the trap. There are surprisingly few cases ruined from direct hits, as the autos throw the cases to the outside of the drum and I fire near the center.

In operation, I always wear a glove to protect my hand from grit or small bits of unburned powder which sting slightly on an uncovered hand. Yes, I have used it without a glove, but I hope you’ll take better care of your hands. I learned without any mishap, but the next person might not be so lucky.

I also wear safety glasses and cover the opening around my forearm with an old car floor mat. The mat is more to contain the sound than for any other reason, but it could serve as a small-particle shield. I always wear ear protection whenever I have a live round in a gun, as I have lost my high-frequency hearing from fuel dragsters, dynamite, and hunting, (nobody wore hearing protection when I was a kid).

After getting used to the trap, I invited the proper deputy sheriff out to my shop to see, hear, and experience the bullet trap. He was skeptical about it until I demonstrated with .22s first, and then with larger rounds in an advancing sequence. I made sure that he knew that it wasn’t for any other person’s use, and that it was only for use with .22 rimfire rifles and handguns up to .44 caliber. He left feeling much better about the shop, and wrote me a note giving me (not customers) permission to use the trap in the course of my business.

Note that there are some feeding problems with automatics which will disappear when the gun is aimed down, but come back when the customer fires it in a level position. I am accustomed to testing for that, and have learned which types of jamming require level shooting.

Have a good time making the trap and be sure to get law-enforcement approval before using it in restricted areas.