One of the best parts of precision rifle shooting is the problem-solving process. Recently at the National Rifle League 22 here in Evansville, Indiana, I came across a new problem. This was the first competition for my customized Ruger 10/22. The rifle is fairly accurate for a low-cost semi-auto. At the beginning of the match, I had verified my zero at 50 yards and confirmed my Dope at 25, 75 and 100 yards. The rifle was performing perfectly.
The first stage of the match was shot from the prone position, but I missed four shots at very easy targets. This confused me a little bit because I could see exactly where the shots were impacting. I could tell they were 0.5 mRad low on my reticle. I have learned to “believe the bullet” from many experiences in the past, so made an adjustment to my hold and hit the rest of my targets.
When the stage was completed, I stood up and began the problem-solving process. I knew that the rifle was zeroed. The ammunition was the same. The prone position was the most stable position available, but I was missing. It was then I realized that when I zeroed the rifle, the bipod was resting gently on the bench. When I was actually shooting the stage, I had hooked the bipod feet into the shooting mat and was driving the rifle with my body weight.
Driving the rifle is a legitimate technique to mitigate recoil and maintain sight picture on a centerfire rifle. The barrels on centerfire target rifles are generally free-floated so that they do not contact the forend of the rifle stock.
The Bell & Carlson Target/Varmint stock on my Ruger 10/22 is designed with a “barrel pad”. This is a high spot in the barrel channel that supports the barrel right at the tip of the forend. This prevents the barrel from “drooping” and can contribute to better accuracy in a 10/22.
I suspected that in my case the barrel pad was providing support for the barrel, changing the pressure at the barrel pad also changed the point of impact. Driving the gun was causing the bipod to act as a lever and moving the barrel pad away from the barrel.
I spent some time on my next practice range day testing this theory. I shot a group from the prone position with the bipod resting on the ground. I then used a wooden strip between two target benches as a brace and “loaded” the bipod hard. I immediately saw a 0.5 mRad drop in the elevation of my group at 50 yards. The accuracy was comparable, but the group was low. This confirmed what I saw during the match.
I had already prepared for this result and brought along a Victor Company USA, Titan 1022 stock. This stock has a very similar shape to the B&C stock, but it is made of polymer and has a fully free-floated barrel channel.
I installed the Titan 1022 and torqued the action screw to 15 in/lbs. My first shot was 2.0 mRad low from the zero with the Target/Varmint stock. I adjusted my zero and shot a group.
With the zero dialed in, I then went back and shot another group with the bipod loaded against the wood strip. There was no change in the group size or elevation. This seemed to support that the bipod was changing the amount of pressure on the barrel and resulting in a variation in elevation.
This test was rather simple, but it demonstrated to me that for this type of shooting, a fully free-floated barrel channel is a better option. Some shooters may not experience this problem. However, my main purpose for NRL 22 competition is to practice the skills I use in long range rifle competition. I do not want to have to change the way I drive the centerfire rifles for a rimfire competition.
How many of you have experienced this phenomenon with your rimfire or centerfire rifles?