When hunting deer in the brush there are several factors worth considering. Short is an advantage when handling a rifle in close quarters like thick brush. And something that you can find a sight picture quickly with is important, as time is always a factor. It must be accurate enough to stuff your shot through small holes in the thick stuff. There must be sufficient "killing power" to make humane kills.
I have heard it said that heavy bullets will buck brush' when hunting. This is incorrect and disastrous thinking. This is simply not the case. Any freely moving object that encounters any other object will necessarily change it's original course according to the forces exerted by the object it encountered. We just can't shoot through stuff, including brush with any
calibre, even big bullets. Soft point or ballistic tip bullets open up on contact with brush, and go off in whatever direction provides the least resistance.
There are a very large number of cartridges for the deer hunter to pick from. I do not recommend any rifle less than a quarter bore (25 calibre) for deer.
Some use 243/6mms for deer, but these small rifles are best left to experts. But you can go all the way to 45-70, or 444 Marlin on the big bore side.
Either of these rounds makes a very potent brush-hunting load in a lever gun. These have the added advantage of being capable of stopping a charging grizzly in its tracks. Sure hope you never need that option. I also think that ammunition should be available over the counter, so we won't discuss wildcats in these sizes.
The 257 Roberts/25-06 size rounds bridge the gap between varmint and deer guns, as do the .264s. In 264/6mm size are the 6.5x55 Swede, 6.5mm Remington magnum, 264 Winchester magnums are all very accurate and potent rounds for deer. Next we find the real "oddball" on our list. It is an odd size, but an excellent round, the venerable old 270 Winchester. This round is arguably the best' deer round ever invented. It, like many other rounds on our list will double nicely for a long-range deer rifle as well. The 284/7mm calibres include the 7x57 and 7mm-08.
These are the two 7mms I would recommend for our brush gun. There are several bigger 7s like the 7x61 Sharp & Hart, or 7mm Remington magnum will certainly fill our bill, but arte surely overkill for deer at close ranges. Many will say that the 30-06/308 cartridges are the "best" round period.
Either will certainly suffice, but again we have almost too much gun for closer shots. Larger 30s than the '06 are assuredly again overkill for deer size critters, as are all of the over 30 calibre "belted magnums". No discussion of deer cartridges could be complete without mention of the 30-30 Winchester. It has killed more deer than any round by good margin, and in Winchester and Marlin lever guns, it continues a fine tradition of getting the first deer for many young hunters. And countless deer for seasoned hunters as well.
From 32 Winchester up to 45-70 there is another list of big rounds that will get our deer from the brush as well as any of the others mentioned. But they are very big rounds for deer. For that reason, I will limit my discussion of them to say that, in my opinion, their only advantage is their protection factor, in case of trouble with dangerous game. Slug shooting shotguns also fit in right here. In 12 or 20 gauge they are popular with some deer hunters, and in some places they are required by law to use them. Great to over 100 yards, and with plenty of power at that range, shotguns definitely go on our list of good brush guns for deer.
We need to find a rifle suitable for our needs. We mentioned the Winchester and Marlin lever guns, and they are great choices. They come in several calibres from 30-30 to 444 Marlin or 45-70. They are light and short, so they handle quickly.
Their open sights are great for quick sighting, and follow-up shots are quickly available if needed. Every imaginable kind of big game is harvested with lever guns each year. Single shot rifles like the Ruger #1, or Thompson Contender are also excellent choices, and come in almost every calibre. The Thompson has the added advantage of interchangeable barrels.
You can have a 25-06 today for antelope, and a 45-70 tomorrow for bison in the same gun. Just change barrels. My personal choice is a 6.5x55 custom Swede bolt-action rifle, shortened to a 22-inch barrel. I like the Mauser bolt-action designs for their durability, simplicity, reliability, and accuracy. A rifle is of no use if it won't shoot, or if it is not accurate. I disregard auto-loading rifles from hunting discussions entirely. They are heavy, dangerous, jam often, and are just grumpy in the field, and need constant attention.
In the brush you don't need a great deal of magnification in a scope.
Iron sights are good as it gets if your eyes are good. I personally use a fixed 4X scope. It is not too much to find the target quickly, and see well at close ranges.
Only this past season I shot a 2-point buck from a range of 25 feet or so. I had no issues with seeing him good enough to shoot in a 4X scope.
There are of course, many other rifles and cartridges out there. Their suitability for deer or any game is often a matter of preference.
I know people who shoot deer with .223 here, because it is legal, but I would never recommend it. And I know a guy who shoots deer with his 375 H&H.
He says it kills them fine. But this was but a general discussion of what is generally accepted as brush guns, not an analysis of every round in the book.