Jan 28, 2010

On Recoil

We've all heard the banter at the range:
"Kicks like a pissed-off mule."
"Kills on one end and maims on the other."
"Bit snappy."
"Barks like hell."

The list of variations is endless, but they all boil down to one thing: a gun that is either recoils hard or has a tremendous muzzle blast. Many shooters combine these things into one item they mentally label "recoil", but they are really two (or even three) separate things.

First, there's recoil. This is simply the gun world's homage to Newton. Any action has an equal and opposite reaction. The bullet sent down the barrel has an equal force pushing the opposite direction: back into the shooter. There's nothing you can do to reduce recoil energy - it's a fixed number. What can be done, however, is to reduce the feeling of recoil. There's two basic ways to do that: increase the weight of the gun, and increase the time over which the recoil is felt.

Increasing the weight of the gun is, of course, simple - and often not desirable. For those who carry pistols, shaving ounces counts; a steel-frame 1911 is nearly three times the weight of an alloy-framed .38 snub. Without getting into the trade-offs there, a lighter gun is easier to carry regularly. In rifles, unless the gun is only carried from the truck to the bench and back, weight matters. Any hunter will tell you just how heavy a 7-pound rifle is after a day in the woods, especially if he's dragging a deer back at the same time.

Increasine the time over which the recoil is felt can be a trickier task, but by no means impossible. Think of the difference between a sharp punch to the shoulder and a hard shove. One hurts, but you can simply ride the other through. The simplest way to do it is to add cushioning to the gun. Numerous manufacturers make butt pads for rifles and shotguns or grips for pistols that cushion the recoil impulse. Well-known brands are Sims Limbsaver, Hogues, Pachy, etc. The other option, especially in long guns, is a recoil dampener. This is a damped weight that recoils separately - and opposite - the gun, reducing the energy that is directly transferred to the shooter.

The final way to reduce recoil is a muzzle brake. This diverts some portion of the propellant gases up and to the sides of the muzzle, effectively pushing the barrel down and pulling it forward from the shooter. A good muzzle brake is highly effective for reducing recoil but at the cost of punishing muzzle blast... which is the second part of "recoil".

To make a gun go bang, powder is burned. That powder burns very rapidly and creates a large quantity of hot gas, which forces the bullet down the barrel and on down to the target. The gas also leaves the barrel at a high velocity, but is expanding in all directions as soon as it is "uncorked" from the barrel. If you've ever seen someone shooting a gun in low-light situations, you're well-familiar with the ball of flame that encompasses the muzzle during each shot. That rapidly-expanding gas pushes a small supersonic pressure wave back towards the shooter. It's loud and can be physically painful with larger guns.

The more powder being burned, or the more powder that burns outside the barrel, the louder and harsher the muzzle blast is. A .22 rifle has almost no muzzle blaast. That same cartridge in a pistol will produce a tiny bit of flash at the muzzle, but blast is still negligible. Step up to the centerfire calibers, and muzzle blast ranges from mild (.223) to mind-bending (.50BMG). How can muzzle blast be reduced? Longer barrels, and no brake.

For example: A Mosin-Nagant 91/30 shoots a 7.62x54R cartridge; it's a military-surplus rifle and was standard issue for many Eurasian armies for several decades. It has a barrel about 24" long, and is an accurate rifle. Hard-recoiling and loud, but not unbearably so. Its cousin, the M-N 91/44, is the same cartridge in a carbine barrel, about 6" shorter. The muzzle blast from that will clear a shooting line in short order, raise huge dust clouds when fired prone, and start grass fires if it's very dry out. The fireball is visible in daylight and generally engulfs the muzzle, bayonet, and as far back as the shooter's support hand. (It should be noted that this fireball only lasts for thousandths of a second, the shooter never feels anything on this hand from it.)

The other alternative, especially for hand-loaders, is light loads, or shooting "Specials" in guns designed for magnums. A light .38Spl load in a .357Mag gun is often a real pleasure, and allows extended practice without abusing oneself too much.

The third and final component of that nebulous recoil cloud is often neglected, but it is worth mentioning. The first two pieces are pretty self-apparent. If the gun hurts the hand or shoulder, and is loud, it's a hard-kicking gun. The final piece, though, is muzzle rise or "flip". This is directly related to the height of the bore over the shooter's hand, the weight of the gun, and the power of the loading. A lightweight load like a .22 or a .38 in a large revolver has minimal flip. The weight of the gun is enough to keep the muzzle roughly on target and not abuse the shooter too much.

In the middle of the road are most of the centerfire automatics, and each of these behave differently. A 9mm often has minimal muzzle flip, as the bore is lower and the recoil energy simply isn't that powerful. A .45ACP in a 1911-style gun will flip more than a 9mm, but less than some other guns. In my own experience, a Sig in .40S&W has more muzzle flip than a 1911 - because the barrel is mounted significantly higher over the grips than the .45.

At the far end of the spectrum are things like the Ruger Super Alaskan (.454 Casull) or Thompson-Center Contender (.30-30 or .45-70). These are massize, heavy guns, but the cartridges they shoot are so powerful that the muzzle will often end up 45 degrees above the initial aim point after firing. In addition to that rise, the gun is often counter-torqued around the barrel as the rifling brings the bullet up to spin. It's an interesting experience to pull a trigger and suddenly find the gun well above your head and turned 30 degrees around the bore.

So with all these things in mind, how does one control recoil? There are no easy answers - Newton doesn't like being ignored. Different grips or a heavier gun can help control some of the felt recoil and muzzle flip. A lighter load may reduce muzzle blast, but sacrifices power. A muzzle brake reduces recoil, but dramatically increases muzzle blast. Everything is a trade off. Beyond that, recoil and perceived recoil are very subjective. I don't mind a hard recoil shove - I shoot 2oz magnum turkey loads every spring and thoroughly enjoyed the .454 Casull and .30-30 Contender - but harsh muzzle blast drives me nuts. I refuse to shoot next to someone with a muzzle brake, and don't enjoy shooting .50s. But that's me. You may be different.

Meantime, I'm going to take the Contender back to the range and see how it does out at 100 yards...

1 comment:

doubletrouble said...

Well done.
It's true- many folks, some who you'd think should know better, label everything that happens after the trigger is pulled as "recoil".

Now I've gotta get back to work on my .50 BMG derringer...