Load Development — Changing "Drivers" Reveals Human Factor in Gun Performance

When developing a load for a new rifle, one can easily get consumed by all the potential variables — load weight, seating depth, neck tension, primer options, neck lube, and so on. When you’re fully focused on loading variables, and the results on the target are disappointing, you may quickly assume you need to change your load. But we learned that sometimes the load is just fine — the problem is the trigger puller, or the set-up on the bench.

Here’s an example. We were recently testing two new Savage F-Class rifles, both chambered in 6mmBR. Initial results were promising, but not great — one gun’s owner was getting round groups with shots distributed at 10 o’clock, 2 o’clock, 5 o’clock, 8 o’clock, and none were touching. We could have concluded that load was no good. But then, another shooter sat down behind the rifle and put the next two shots, identical load, through the same hole. Shooter #2 had his own issues with the bag and rest and eventually produced a 6-shot group that was a vertical line, with 2 shots in each hole but at three different points of impact. OK, now we can conclude the load needs to be tuned to get rid of the vertical. Right? Wrong. Shooter #3 sat down behind the gun and produced a group that was pretty much a horizontal line with almost no vertical. Hmmm… what gives?

Well each of the three shooters had a different way of holding the gun and adjusting the rear bag. Shooter #1, the gun’s owner, used a wrap-around hold with hand and cheek pressure, and he was squeezing the bag. All that contact was moving the shot up, down, left and right. Shooter #2 was using no cheek pressure, and very slight thumb pressure behind the tang, but he was experimenting with different bag positions. His hold eliminated the side push, but variances in bag position and down pressure caused the vertical string. When he kept things constant, the gun put successive shots through the same hole. Shooter #3 was using fairly heavy cheek pressure. This settled the gun down vertically, but it also side-loaded the rifle. The result was almost no vertical, but a lot of horizontal.

A “Second Opinion” Is Useful
Conclusion? Before you spend all day fiddling with a load, you might want to adjust your shooting style and see if that affects the group size and shape on the target. Additionally, it is nearly always useful to have another experienced shooter try your rifle. In our test session, each time we changed “drivers”, the way the shots grouped on the target changed significantly. We went from a big round group, to vertical string, to horizontal string. Interestingly, all three shooters were able to diagnose problems in their shooting styles, and then refine their gun-handling. As a result, in a second session, we all shot that gun better, and the average group size dropped from 0.5-0.6 inches into the threes.

That’s right, we cut group size in half, and we didn’t alter the load one bit. Switching shooters demonstrated that the load was good and the gun was good. The skill of the trigger-puller(s) proved to be the limiting factor in terms of group size.