The way this thing works is probably self evident from looking at the picture above. However, what you do is place a 32 APC cartridge in the end of the adaptor. The adaptor is then hand loaded into your rifle and fired. The 32 APC pistol bullet diameter of .311 is close enough to the normal .308 rifle bullet size that it goes through your rifle barrel with no problems. You will normally need to use a pencil to push the spent 32 APC cartridge out of the adaptor base. It does not require much of a push and sometimes they fall out by themselves.
To initially use the adaptor you will probably need to adjust the adaptor length to fit your chamber by sanding the head end on some emery cloth as directed by the instructions enclosed with the adaptor. I used a small square of 120 grit emery cloth from my tool box that I find occasional use for. What you do is hold the emery cloth on a hard smooth surface. Then you place the head of the adaptor down on it and sand the end using a circular motion. Check it occasionally in your rifle action until the action just closes easily. I suggest you try and remove the circular swirls on the head end before firing it in your rifle by using a finer grade of sand paper than I did. I believe that swirl marks left on the end of the adaptor were transferred to the end of my bolt during firing.
Even if you have something other than a single shot rifle you will still have to load and fire the pistol cartridges like you would with a single shot rifle. The pistol round does not have enough power to cycle semi-auto rifles. Also the pistol cartridge can easily slide back out of the adaptor. So if you tried to load several adaptors and put them into your magazine you might find that a pistol cartridge had fallen out during the cycling since the 32 APC has an easy slip fit into the adaptor. Also, since the adaptor is shaped like an empty rifle case it lacks a rounded bullet shape at the end that most guns count on to guide the cartridge into the chamber. So you would most likely have my experience of discovering that the adaptor cartridge mouth gets caught while moving from the magazine into the chamber. Finally you want to avoid the gun action throwing your $15+ dollar adaptor off into the weeds or onto the concrete floor. I let mine hit the concrete once and the cartridge mouth was bent slightly. It straighten out with the next shot but I decided that I needed to catch it each time with my hand as it came out of my action rifle.
The Sportsman’s Guide product information page says “If you have a .308, .303 or .30-06., you can make it more "town-friendly" quiet, and practice shoot it for less.” It further says, “The gun becomes low recoil and low noise (similar in volume to a magnum air rifle).” I think that the noise statements are mostly false. When I fired a Remington UMC practice cartridge the noise sounded like a regular 22LR rifle cartridge due to the supersonic speed of the gasses exiting the barrel. I think that is too loud to be called “town friendly.” Since I had been interested in some backyard quiet firing I did a test reloading the 32 APC shells to find out at what point they did become quiet. What I finally came up with was that I could put no more than 1 grain of Clays powder under a 71 grain metal case bullet for the combustion gasses to be subsonic when they exited the muzzle of my 22” long barrel. The average bullet velocity was 637 FPS. At that point the sound was more of a loud pneumatic blast that lacked the “crack” typical of supersonic gasses. I had also tried a 49 grain “O” buck shot but it lacked the weight necessary to obtain good combustion and the exiting muzzle gasses were louder and had something of a supersonic “crack” with the same powder load.
Typical muzzle velocity from a pistol for my factory test Remington UMC cartridge is 905 FPS according to Remington. The average muzzle velocity from my rifle was 1095 FPS. Pistol cartridges are meant to fully combust in just a couple inches so the long barrel length only added around 17% more velocity.
The adaptor really hurt the rifle accuracy. Typical 5 shot group sizes at 25 yards were from 1 ½” to 2 ¼” using a 71 grain bullet. That was a little distressing so I went and got my normal 150 grain 308 Winchester hunting reloads and shot a ½” 3 shot group that I felt much better about. These were all shot sitting at a picnic table and holding the rifle with my elbows rested on the table. A 2 ¼” group accuracy is bad enough that I would hesitate to use this adaptor for squirrel hunting. I would certainly not go for the head shots that would be fine with a scoped .22LR rifle. Also the point of impact shifted to the right a couple inches from the settings normal for my deer hunting load.
Sportsman’s Guide only sells the most popular size version. However, MCA Sports (http://www.mcae.com/) sells 34 other versions for a variety of .22 .30 and .32 pistol calibers fired in various rifle cartridges. By the way Sportsman’s Guide calls this product an Insert. MCA Sports calls it an Adaptor. I think the Adaptor term is more correct.
Overall this adaptor has limited usefulness. Accuracy is reduced and handgun cartridge cost is much higher when compared to plinking with 22LR cartridges. It could possibly be used to introducing a youth to a larger rifle where you initially want to avoid recoil and don’t want to mess with hand loading some low recoil cartridges. However, since the rifle function would be different than normal that does not seem like a good training route. Finally, if you want low noise for backyard plinking or pest control then CCI 22 Short CB or Remington 22 LR CBee cartridges seem like the way to go for less money, more convenience, and more accuracy.
