If your deer rifle kicks you so badly it causes you to flinch, you’ll never be a consistently good field shot. For that reason, selecting a cartridge that will not kick you like a mule is an important, if sometimes overlooked, part of selecting the ideal deer cartridge.
Free recoil describes the rifle moving backward unrestrained at the shot, and is generally described with two measurements—free recoil energy and recoil velocity. It is calculated by a mathematical formula based on Newton's basic law of physics, which states that for every action there is an equal and opposite reaction. There are four primary factors considered when calculating recoil—bullet weight (mass), bullet velocity, powder charge and rifle weight (mass). In this calculation, MV (mass x velocity) of everything ejected from the rifle’s muzzle—mostly the bullet and powder gasses—will be equaled by MV of the recoiling rifle.
Generally speaking, the faster a rifle comes back at the shooter, the more it hurts. This is because your body has less time to move with the recoil. Suffice it to say that, all things being equal, the faster the bullet, more felt recoil is generated, while heavier rifles produce less felt recoil.
Of course, we all feel recoil differently. A heavier person will be able to absorb more recoil than a smaller, lighter person, for example. There are also some things you can do to help tame felt recoil. These include making sure the rifle stock fits well, and attaching the stock with a quality recoil pad. (You can also add a muzzle brake, but this should not be necessary with most standard deer cartridges.) Also, gas operated semi-automatic rifles like the Browning BAR and Remington Model 7400 reduce perceived recoil by spreading it over a longer period of time.
Perhaps the best thing you can do is to avoid using ultra-lightweight rifles. For any given caliber and load, a lighter rifle kicks more than a heavier rifle. Generally speaking, a 6 ½ pound ultra-light rifle will generate about 20 to 25 percent more felt recoil than an 8 ½ pound rifle when shooting the exact same load.
So, how much felt recoil is too much for the average shooter? That’s impossible to say, of course, since we’re all different. For most deer cartridges, it is generally accepted that 20 ft./lbs. of free recoil energy and 15 ft./lbs. of recoil velocity are the approximate upper limit of comfort level for most of us. There are many recoil tables available online; one excellent one can be found at Aquila Firearms.