50yds
The brush rifle, and brush rifle cartridges are one of those topics that have been debated many times, and will continue to fuel hunt club arguements and online forums. We typically cannot predict where and how we see game, and limiting ourselves to a short range only type firearm limits our chance for success on some hunts. But, if there are conditions where short range will indeed by the circumstances, I'm thinking bayed hogs, treed cats,
then a brush rifle would be acceptable.
The brush "rifle" needs to be short and light for a couple of reasons. (no offense intended for the fella with the .50 Sharps) One is you've got to get the rifle through the brush. Long barreled rifles (and shotguns) are a pain to get through thick stuff, either in hand or slung. Which brings up the next point....if your hunting in the brush, just not covering ground but expecting to get a shot on foot, you will need the rifle in your hands, not slung. A lighter gun will carry easier, in hand, over the long haul.
I think a brush rifle needs the capability for a fast repeat shot. Whether hunting rutting bucks, that can flash through a crossing while chasing a doe, or game driven by hounds or an ill tempered hog, we do miss, or hit limbs , stuff happens. The ability for a quick second shot is then fully appreciated. I'm not talking about unethical shots or blazing away randomly, simply saying that there are occasions where a quick follow up is advantageous. For me, that puts the bolt rifle in last place. I consider myself an able rifleman, but cannot run a conventional bolt as fast as I can deliver aimed repeat shots with a semi, pump, or lever, likely in that order.
I have seen video of the Euro folks shooting boar with straight pull bolts.....but that is another story. Have you noticed that most of that type of shooting seems to be done done down shooting lanes or on field edges, locations with defined and open fields of fire? They often do it with full size rifles, but are likely dropped at the stands by vehicle, and often shoot from elevated and clear platforms. Just not the same as sidehilling a hardwood ridge all morning below a pine plantation, looking for for a whitetail returning to bed.
Sights....50 yds and in is darn close, if I were not such an old school guy, I'd say that a red dot, a good one, would be the sight of choice. I still have a hard time accepting batteries on my firearms, but do realize that the military and competitive shooting has pretty much proven the dot sight...it's just me.
After that, a low powered variable with a big bold reticle. My brush rifles have 1-4x scopes w/ German #1's on them.
The cartridge? That's the fly in the ointment. I have no belief at all that I can chop through brush to get a predictable, killing shot on a deer with any caliber. I suppose if you compare extremes (say .17 Rem v. 45-70), through thin cover like a a screen of sage right next to your animal, you can make the arguement. But typical deer calibers are going to deflect and deform when encountering an limb of any size, and your point of impact will be random, and the closer to the muzzle, the worse the problem. I can accept a moderate cartridge for my hunting, which is typically from climbing stands, in woodlands, and ranges are short, though they will go over 50, they are almost always under 100. I know where I will hunt an on most any given outing, and in the very rare instances when I hunt on large food plots from shooting house or box blinds, or on open ROWs, I simply take a bigger rifle.
Typically, I'll keep a spare rifle in the truck anyhow, and usually it's GP in nature, often the .308 Savage Hog.
My dedicated brush/treestand rifles? Most often, a vintage Ruger .44 carbine (tube feed). Another is a Mini30. Both have the 1-4x mentioned. The .44 is so short and light it will spoil you. Terrible trigger, so-so accuracy, but over the years very reliable, and is grim death inside 100 yds. Most of the venison it's collected has been well under half that distance. The Mini30 is a tad heavier but falls into the same category.