Up next is a heavy barrel AR-15, shooting right off the edge of the handguard and at the end of the barrel. At the edge of the handguard, the shift is 3.5″ at 50 yards. Resting on the end of the barrel produced a 7″ shift at 50 yards. As this test demonstrates a stiffer barrel will reduce the amount of shift but will still cause a loss in accuracy.
Different Rifles, Different Results
Now for something completely different, a Galil ACE with a 16″ barrel in 5.56. Since the barrel on a Galil is not free floated, like the AR, there is more rigidity. Shooting off the edge of the handguard produces about an inch shift. However, shooting from the end of the barrel produces about a 4″ vertical shift at 50 yards. The first group is shot by resting on the barrel right at the gas block. Because of the piston system, this part of the barrel is still very stiff and there is little flex.
Lastly, we have the Savage bolt action with a heavy barrel. Besides the Galil, this rifle showed the least amount of impact shift. 1″ shift from the edge of the stock and 4″ shift at 50 yards shooting from the end of the barrel.
Notice that we have not talked about barrel harmonics. This test doesn’t really illustrate the effect that harmonics play on the barrel, that is a video for another time. What this shows is that the pressure put on the barrel from resting it on a surface will cause barrel flex and an impact shift.
In summary shooting by resting your barrel on anything is bad! The flex in the barrel causes a point of impact shift that can cause you to completely miss the target even at short ranges. The further out you shoot the more extreme the shift in impact is.