Advances in technology and trends of market whimsy have done nothing to stifle the discourse about which rifle "bucks the brush" better. Hunters of the old school say that a heavy, fat, blunt-nosed bullet traveling at low to moderate velocity will plow through brush with less deflection. The "enlightened" modern thinkers say that the long, thin bullet with a high rate of rotational speed will perform better because the gyroscopic effect of the rotation will keep it on course or aid it in returning to a stable course after a disturbance.
Then there is the matter of bullet construction. Certainly, a low-velocity bullet will need to be of a softer construction than a premium bullet designed for magnum-type impact velocities. It follows that the softer bullet will deform more easily than the tougher "modern" bullet and destabilize in flight. That is certainly true if the velocities are the same, but the very natures of the bullets dictate that the tougher bullet will be traveling at a higher velocity. What effect will that create?
Finally, there is the argument that in a given caliber, a round-nosed or flat-nosed bullet is better for shooting through brush than a pointed bullet. Nobody seems to know why, but a lot of hunters will argue the point passionately.
I have heard arguments on the extremes of both sides. A Saskatchewan outfitter once told me that his .35 Whelen would mow down the thick second-growth brush that dominates the east side of the province like a "weed whacker through your front lawn." On the other hand, a manufacturer of a gun-related product told me during a SHOT Show dinner that if a bullet traveling over 3,500 fps even comes close to a tree branch, without necessarily hitting it, the pneumatic pressure of the air displaced by the bullet compressing against the tree branch will cause the bullet to fly off course and often even disintegrate in flight.
So who can you believe?
Testing The Theory
I think that it is accepted that any bullet will deflect in flight if it hits brush. My grandfather's response to this was, "If you can see the deer well enough to shoot at it, then there is a hole big enough to fit a bullet through without hitting the brush." Good advice, but it still doesn't answer the question of bullet deflection.
To find out for myself, I decided to shoot several rifles through brush under controlled conditions and record the results. Because using actual brush provided inconsistent results, I turned to hardwood dowels to simulate brush.
I drilled holes in a couple of two-by-fours to hold the 1-foot dowels. The holes were carefully spaced with 1/8-inch between them to ensure that no bullet could slip between without hitting something.
Because the target backstop on our range is higher than the bench inside the shooting house, I constructed a frame to hold the "brush" high enough to approximately center the groups on the plywood backstop. A target was hung between cross-members on the front of the frame. This was placed at a measured 10 yards in front of the backstop, which was 100 yards from a shooting house. One foot behind the target was a barrier of 3/8-inch dowels. This was designed to be about twice as wide as the front barrier so that it would catch any deflected bullets.
I covered the backstop with white paper, and shooters fired three shots at that target with each gun without the "brush" in place to establish a center of impact on the backstop. Unless noted, we then fired five shots through the "brush" from each rifle. After each shot, we replaced the dowels and marked the resulting hit on the backstop. This ensured consistency in the "brush" encountered by all bullets.
All shots were fired from a bench rest, and caution was taken to make sure that they were carefully aimed. However, since I was recording the differences in group sizes before and after hitting the brush and the deviation from the center of impact, exacting accuracy was not necessarily important. All rifles showed acceptable hunting accuracy with the ammo selected, but the results are not to be interpreted as the "best" that rifle can shoot.
Analyzing The Results
The results are recorded in the accompanying chart, but I will note some key points. Long, pointed bullets tended to keyhole (turn sideways), particularly when they hit the first dowels a glancing blow that put them between two dowels. Often, the second barrier would have two or even three dowels cut off, indicating that the bullet was traveling sideways.
Round- or flat-nosed bullets tended to track better and showed less tendency to keyhole. The old-timers who liked big, slow bullets were on to something. The .35 Rem., .44 Rem. Mag. (discounting one flyer) and .45-70 showed the lowest percentage change in group size.
To spoil the theory, the .270 Win. showed no change in group size if you discount the one flyer.
Check out the .308 Win.! It actually showed a smaller group size after hitting the "brush." All calibers showed evidence of losing stability or deforming.
In summary, you would be ill-advised to intentionally take any shot through brush at a deer. Every bullet that hits brush, regardless of caliber or design, will be affected, and it is impossible to predict reliably what that affect will be. While one caliber might do "better" than another, they all had the potential for extreme flyers. If that flyer happens to be the shot you fired at a buck, the results could be disastrous. Nothing's worse than making a poor hit n a magnificent game animal.