Thursday, April 9, 2015

Size Matters & Newton’s Third Law of Physics Applies to Firearms

Size Matters & Newton’s Third Law of Physics  Applies to Firearms

Newton’s Third Law - When one body exerts Force (Mass X Acceleration) on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body. - Isaac Newton

All too often, I hear new shooters say that they do not like recoil so they want to buy a small dinky lightweight handgun. Well unfortunately, Mr. Newton would vehemently disagree with them on this common misperception.  The main problem is that a "small" sub-compact gun half the size and a quarter the weight of a full sized handgun is typically not shooting a round 50%-75% less powerful. Most are still shooting the same 9mm or .38 Special ammo in just a smaller sized gun. The result is that when all the power contained in the round is let loose from pulling the trigger, approximately 300-400 ft/lbs of energy, the bullet energy going forward must be completely managed via the mechanical internals of the gun, leverage, or weight or you will feel recoil. The reality is that no gun manages recoil completely and you will feel some degree of recoil; sometime less, sometimes more.

A 9mm powered custom Salient International
Glock 17 is a delight to shoot.
Especially with handguns, size does matter and in almost all cases, a larger heavier gun will shoot with greater control, be easier to operate, deliver better accuracy, and deliver far less kick/recoil to the shooter. In most cases this rule also applies to revolvers as well.

TRANSLATING NEWTON’S THIRD LAW FOR FIREARMS - No matter how you slice it according to old Newton, when you have 400 ft/lbs of energy leave the front of the barrel, force equaling that 400 ft/lbs of energy is coming back into your hand and it needs to be dissipated in some way.
Kahr's tiny 9mm CM9 shoots the same
ammo as the the Custom Salient
Glock 17 above and its snappy
to shoot.

When one body (the explosive energy and recoil of the round going off) exerts Force (Mass of the bullet X Acceleration of that bullet) on a second body (the Shooter), the second body (the Shooter) simultaneously exerts a force equal in magnitude and opposite in direction on the first body (the recoil from the round going off).

Without getting into a giant physics lesson, basically when something like a gun recoil pushes on your hand and your connected body, you push back with approximately the same force. Some of the felt recoil energy can be dissipated by things like weight, mechanical internals of the gun, friction, shooter’s leverage on the gun, muzzle flip, compensators…and many other things.
Ruger's 17oz 9mm LCR shoots the same
ammo as the the Custom Salient
Glock 17 above.

Weight is one of the most significant factors to reducing recoil. If you get a gun heavy enough, recoil can be nearly eliminated unless you start increases the power of the cartridge as well. Weight is one reason the giant 6” Ruger GP-100 in .357 Magnum is a favorite of mine. With standard .357 Magnum loads the huge heavy pistol is a blast to shoot with very little recoil due to the weight. Take that same .357 Magnum round and drop it in a Desert Eagle Semi-Auto pistol with even more weight plus a gas driven semi-auto action and you feel like you are shooting almost a rimfire cartridge thanks to the weight and semi-auto action. Toss that same .357 Magnum round in a uber-light 17oz  Ruger LCR and your hand, arms, and body and the experience become more abusive to the body. Weight is one reason the not particularly light 1911 style pistols are so pleasant to shoot. For a home defense handgun, do not be afraid of a bigger and heavier gun. The weight will make it one of your favorite guns to shoot which will make you want to train and practice more.
These are all 9mm handguns with the
exception of the bottom right Ruger .380 LCP
The Top Left Glock 19 obviously has the least recoil

Revolvers unfortunately cannot mechanically manage recoil like a semi-auto can, so most shooters will note in a side by side test that a small .38 Special snub nosed revolver will deliver more recoil than a similarly weighted, powered and sized 9mm compact semi-auto pistol. Revolvers are without question easier to operate for novice shooters, however the semi-autos are drastically more comfortable to shoot. The main reason for this is that the semi-auto spring/slide action absorbs/manages some of the recoil by using it to cycle the firearm. This semi-auto mechanism also distributes the recoil impulse over a short period of time while the slide and spring cycles the action and creates a buffering effect on recoil. This is the same reason we bend our knees jumping off a chair - we can distribute the impact energy over a period of time using our knees as a spring versus locking out our knees and jackhammering ourselves into the floor. On revolvers, there is nowhere for the energy to go which is not compensated by weight or leverage, so a larger percentage of the recoil is felt by the shooter.

Extending this concept to rifles and shotguns, bolt action and pump action shotguns without question deliver more recoil to the shooter than a semi-auto rifle or shotgun action simply because the semi-auto action can absorb more of the recoil energy. At one time I had an old Savage 12 Gauge bolt action shotgun and it was downright abusive to shoot, my Browning A5 is of course a dream with very little recoil.

The cycling of a semi-auto action burns off some of the recoil energy in the form of slide friction, spring tension, potentially the flex of the polymer lower receiver, slide weigh cycling, and other friction points. If you want lower recoil buy a semi-auto action pistol, rifle or shotgun.

As noted above, a bigger and longer semi-auto handgun will deliver less felt recoil and a full grip (versus two or three finger grip) will increases leverage/control when hand cycling the gun.

Ruger's 9mm LCR uses "moon clips"
to hold the rounds instead of magazines.
Improved shooter leverage with a full sized grip and more pistol weight/length out in front of the hand ultimately delivers a softer feeling recoil because more weight of the gun can work to control recoil when compared to the same round being fired in a smaller shorter gun.

Revolvers are typically designed to place the grip very far rearward and low compared to the bore axis to maximize leverage and decrease recoil. However despite weight and this rearward leverage advantage, revolvers generally still deliver heavier recoil to the shooter than an equivalently heavy semi-auto.

Tiny little semi-autos still have to manage at least some of the recoil to reliably cycle the round. Too little recoil or too much and the gun just will not cycle properly. So that generally means all that compressed spring force of a longer recoil/slide spring of a longer gun now needs to be extra stiff in a tiny little gun. A very stiff recoil/slide spring of course makes charging these dinky guns somewhat challenging for those with less hand strength… and if you can’t get rounds in your gun, that does tend to be a problem. For new  or less muscled shooters, this is “the” one reason I tend to recommend revolvers in the small sized category such as the new Ruger LCR 9mm. You will suffer more recoil, however you will more importantly be able to operate the gun. That same new  or less muscled shooter would likely be able to operate a Glock 19 just fine, however once you go small, the shooter has to start dealing with a very stiff recoil spring which can make manipulation less than forgiving and more problematic even for bigger, stronger, and trained shooters. If you decide to carry a dinky little semi-auto, I recommend without reservations carrying the gun always with a round in the chamber. I have never felt comfortable with my own reliability of performing the Massod - Draw, Charge, Shoot method with tiny little semi-auto pistol.

The mass and leverage of this Ruger tames
even the hottest .357 magnum loads
Bigger Semi-Auto Gun = Less Spring Tension, More Weight, More Shooter Leverage
1st Class Lever and Less Recoil

Bigger Revolver = More Weight, More Shooter Leverage, and Less Recoil

In the case of recoil reduction, bigger is better, however due concealment, size, and weight limitations we obviously are not going to all carry around Desert Eagles and Ruger GP100s with 6" barrels. Handguns like Glock 19s, Glock 26, Walther PPS, and H&K P30s are more typical as concealed carry handguns... or at least that is what I carry.

The giant Magnum Research Desert Eagle requires
the hottest .357 Magnum loads just to operate
reliably and still delivers a soft recoil.

Reasonably sized handguns end up being the choice and sacrifice that we all make to absorb a bit more recoil instead of requiring a chiropractor once a week from lugging around a backbreaker of a gun. There is a place for teeny weeny little guns, however that should be left to situations only where concealment or extreme convenience dictate a diminutive sized gun. 

My advice for a first time gun buyer is to choose a firearm with a comfortable full sized/four finger grip, semi-auto action, and a size in the mid range size such as the H&K VP90, Walther PPQ M2, or Glock 19, but if you need something smaller just expect to manage recoil.

Newton was right, however convenience sometimes overrides even Newton's laws of physics.

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