JDinFbg
Member
Around the first of the year I embarked on a project to construct a machine rifle rest for testing hand loads in the rifles I own. In testing hand loads, when one does not achieve the results one hoped for, there are always the nagging questions of whether the problem is the rifle, a sight or sight mount issue, the inability of the shooter (that would be me) to get a consistent sight picture each shot, and all of the sundry factors that affect the ability to find a load that achieves a small group size. Further, on the rifles I own that only have iron sights, my old eyes would not allow me to get anywhere close to being able to differentiate the viability of one load versus another. Additionally, in developing loads for a rifle, one can burn through hundreds of rounds of ammo to find the optimum load, and not having to endure the wear and tear on my shoulder is certainly a plus for having a machine rifle rest, especially when testing large-caliber rifles.
So, that is the genesis for my desire to have a machine rifle rest. I discovered that there are some commercially made machine rests out there, but I was not particularly impressed with what I saw. Further, I'm always interested in having a project as much as the end result, so I decided to build my own. For better or worse, I've attached some pictures of what I built. Without question I put way more steel in this thing than was needed (the carrier that holds and moves with the rifle recoil weighs 71 pounds), and in hindsight I probably would build it differently if I were doing it again. Hey, it is said that Thomas Edison did not have any failures in developing the incandescent light bulb, he learned thousands of ways not do build the bulb.
I did run down a rabbit hole or two in my initial design which became evident when I first tested the machine rifle rest at the range. The main problem with my initial design was with the rifle butt clamping mechanism which was also the facility for making the needed windage adjustments. The first picture is of my initial design for the butt clamping mechanism. This relied on two opposing, 3/8" hand screws to clamp the butt of the rifle and allow me to adjust the windage. The mechanism had enough play so as to allow the rifle to twist slightly in the clamps during recoil. Further, in making windage adjustments, the twisting action of the hand screws transferred to the rifle making the adjustment difficult. Also, I realized that the strapping mechanism I chose to hold down the forearm of the rifle needed to be changed. The second picture shows the binder strap I used for securing the forearm of the rifle. I used a pull-tight type nylon binder strap I already had, but realized that in this application I could not pull the strap tight enough to firmly hold the rifle forearm.
I quickly realized the deficiency of my initial design, so it was back to the shop to devise an alternative. Luckily, I was able so salvage the majority of what I had built and with a small investment in some additional steel and materials and a lot of cutting and grinding to remove my "mistake", I was able to produce a machine rifle rest that worked to my satisfaction and achieved what I was after.
The third picture is a view of the revised butt clamping facility I built, and this puppy clamps the rifle butt rock solid. To provide for needed windage adjustment of the rest as shown in the fourth picture, I installed an additional steel plate to the rear of the rest base which rides on a steel plate that gets bolted to the bench and has a bolt for locking the rest in place. This allows the entire rest to swivel but maintained the bolt pattern to match the mounting holes I had drilled in my shooting bench. The fifth picture shows the completed redesigned machine rest in my shop. The last picture is of the rest at the range with my Model 94 Winchester clamped in it during my recent tests.
This machine rifle rest allowed me to develop a new load for my 94 Winchester using the Hornady 160 gr. FTX bullet and identify the powder level that produced the smallest group (shown in the attached PDF). For this group, 4 of the 5 shots had a 0.722" group size. Given that my 94 only has open sights, it would have been impossible for me to differentiate which load produced the smallest group if I had been shooting from sandbag rests. The machine rifle rest made this possible, and I didn't have to endure the recoil from the 50 rounds I shot during the testing.
So, that is the genesis for my desire to have a machine rifle rest. I discovered that there are some commercially made machine rests out there, but I was not particularly impressed with what I saw. Further, I'm always interested in having a project as much as the end result, so I decided to build my own. For better or worse, I've attached some pictures of what I built. Without question I put way more steel in this thing than was needed (the carrier that holds and moves with the rifle recoil weighs 71 pounds), and in hindsight I probably would build it differently if I were doing it again. Hey, it is said that Thomas Edison did not have any failures in developing the incandescent light bulb, he learned thousands of ways not do build the bulb.
I did run down a rabbit hole or two in my initial design which became evident when I first tested the machine rifle rest at the range. The main problem with my initial design was with the rifle butt clamping mechanism which was also the facility for making the needed windage adjustments. The first picture is of my initial design for the butt clamping mechanism. This relied on two opposing, 3/8" hand screws to clamp the butt of the rifle and allow me to adjust the windage. The mechanism had enough play so as to allow the rifle to twist slightly in the clamps during recoil. Further, in making windage adjustments, the twisting action of the hand screws transferred to the rifle making the adjustment difficult. Also, I realized that the strapping mechanism I chose to hold down the forearm of the rifle needed to be changed. The second picture shows the binder strap I used for securing the forearm of the rifle. I used a pull-tight type nylon binder strap I already had, but realized that in this application I could not pull the strap tight enough to firmly hold the rifle forearm.
I quickly realized the deficiency of my initial design, so it was back to the shop to devise an alternative. Luckily, I was able so salvage the majority of what I had built and with a small investment in some additional steel and materials and a lot of cutting and grinding to remove my "mistake", I was able to produce a machine rifle rest that worked to my satisfaction and achieved what I was after.
The third picture is a view of the revised butt clamping facility I built, and this puppy clamps the rifle butt rock solid. To provide for needed windage adjustment of the rest as shown in the fourth picture, I installed an additional steel plate to the rear of the rest base which rides on a steel plate that gets bolted to the bench and has a bolt for locking the rest in place. This allows the entire rest to swivel but maintained the bolt pattern to match the mounting holes I had drilled in my shooting bench. The fifth picture shows the completed redesigned machine rest in my shop. The last picture is of the rest at the range with my Model 94 Winchester clamped in it during my recent tests.
This machine rifle rest allowed me to develop a new load for my 94 Winchester using the Hornady 160 gr. FTX bullet and identify the powder level that produced the smallest group (shown in the attached PDF). For this group, 4 of the 5 shots had a 0.722" group size. Given that my 94 only has open sights, it would have been impossible for me to differentiate which load produced the smallest group if I had been shooting from sandbag rests. The machine rifle rest made this possible, and I didn't have to endure the recoil from the 50 rounds I shot during the testing.
