This topic is the age old discussion that is ongoing in most IDPA and USPSA clubs.  The first time some one told me a heavier bullet has less recoil, I though they were nuts.  After all Newton’s Third Law tells me that:

For every action, there is an equal and opposite reaction.

Logic would dictate if you increase the weight of the bullet the recoil would also be increased. Thus a heavier bullet should have a heavier recoil, conversely a lighter bullet would have a lighter recoil. One thing that is often overlooked in the concept of a “heavier bullet has a lighter recoil” is the fact that part of the statement is left out; as I found through some basic research.

I started my research by looking up the mechanical physics concepts for both of the measurable elements.  The measurable elements, in this case, are the Recoil (Newton’s Third Law) and the Power Factor (Momentum)

Newton’s Third Law

For every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object. The direction of the force on the first object is opposite to the direction of the force on the second object. Forces always come in pairs – equal and opposite action-reaction force pairs.
via Physics in the classroom.

Momentum

In classical mechanics, momentum is the product of the mass and velocity of an object (p = mv). It is sometimes referred to as linear momentum to distinguish it from the related subject of angular momentum. Linear momentum is a vector quantity, since it has a direction as well as a magnitude.
via Momentum – Wikipedia, the free encyclopedia.

Measuring Recoil

In this case, to measure the recoil, I am relying on the fact that Newton’s Third Law is correct, and the hypothesis that the muzzle energy of a bullet (the force at which the bullet is traveling away from the gun) will translate into recoil acting on the gun.

For example a 124 grain bullet traveling 1008.6 feet per second (FPS) has a muzzle energy of 280.04 foot pounds (Ft-Lbs). Multiply the product of the weight of the bullet (in grains) times the velocity squared and divide by two times the acceleration  of gravity (32.174 FPS) times 7,000 grains per pound.

• (124 * (1 008.1^2)) / (2 * 32.17400 * 7 000) = 279.766572

Measuring Momentum

To measure the momentum of the bullet I simply used the IDPA formula for determining power factor which is identical to the momentum formula for physics. For example the Power Factor of a 124 grain bullet traveling at 1008.6 FPS is 125,066.

• 124 * 1,008.1 = 125,004.4

Putting it All Together

If I take the formulas and concepts above and do some quick calculating using a 124 grain 9mm vs. a 147 grain 9mm bullet, both at a 125,000 power factor (PF) I find the following:

Velocity required to make 125,000 PF

124 grain bullet = 1008.1 FPS

• 125,000 / 124 = 1 008.06452

147 grain bullet = 850.3 FPS

• 125 000 / 147 = 850.340136

Muzzle Energy at 125,000 PF

124 grain bullet = 280.04 Ft-Lbs

• (124 * (1,008.1^2)) / (2 * 32.17400 * 7 000) = 279.766572

147 grain bullet = 235.95 Ft-Lbs

• (147 * (850.3^2)) / (2 * 32.17400 * 7 000) =235.954682

So how is it all possible? How is it that the heavier bullet has 45 foot pounds less recoil?  The answer lies in the mathematics used to calculate each factor.  While Energy increases exponentially as the velocity increases the Power Factor only increases linearly.  Thus by increasing the bullet weight and lowering the velocity to meet the power factor, the energy is exponentially reducing from the drop in velocity, while the power factor remains constant. So next time you hear “Heavier bullets have less recoil”  make sure you correct the statement to its true form: “Heavier bullets have less recoil, if the power factor is held constant.”

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The folks from ammunition accountability are at it again this year.  Although this piece of legislation keeps dying every time it is proposed, they are trying again. There tag line of saving lives one bullet at a time is comical at best.  The system has many conceptual problems, including increasing the manufacturing cost of ammunition, as well as local, state and federal agency administrative cost.  The thought that one could track a criminal through a registered bullet is a little far fetched. 

What makes one think if criminals steal guns, and deface serial numbers on guns, they will not do the same for ammunition?   

From WND:

Group asks states to track citizens’ ammo
Organization claims it is ’saving lives 1 bullet at a time’
By Chelsea Schilling
© 2008 WorldNetDaily

Legislation to trace ammunition is pending in several states, and many gun owners are concerned that it is just another attempt by anti-gun groups to violate citizens’ Second Amendment rights.An organization known as Ammunition Accountability is pushing to make coding technology mandatory across the nation. Its website claims it is a group of “gun crime victims, industry representatives, law enforcement, public officials, public policy experts, and more” who are “saving lives one bullet at a time.”

If states pass the legislation, manufacturers will be required to laser etch a serial number into the back of each bullet and the inside of cartridge casings, a patented process developed by Seattle, Wash., resident Russ Ford and his business partners, Steve Mace and John Knickerbocker.

According to Seattle Weekly, the men couldn’t find an ammunition manufacturer to agree to stamp bullets, so they hired a lobbyist to push for state legislation to require the laser coding. They launched the Ammunition Accountability website and successfully introduced bills in the following 18 states: Alabama, Arizona, California, Connecticut, Hawaii, Illinois, Indiana, Kentucky, Maryland, Mississippi, Missouri, New Jersey, New York, Pennsylvania, Rhode Island, South Carolina, Tennessee and Washington.

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Fox News is reporting Heller is back at it. Heller and two others filed a federal lawsuit against Washington DC for having overly restrictive gun regulations, now that the gun ban has been overturned.

Gun Ban Plaintiff Dick Heller Files New Lawsuit Against Washington, D.C.

Monday , July 28, 2008

WASHINGTON —AP

The plaintiff in the Supreme Court case that overturned Washington’s 32-year-old handgun ban has filed a new federal lawsuit against the city.

In a complaint filed Monday in U.S. District Court, Dick Heller and two other plaintiffs allege that the city’s new gun regulations still violate rights guaranteed under the Constitution.

The lawsuit cites the District of Columbia’s unusual ban on firearms that carry more than 12 rounds of ammunition, which includes most semiautomatic handguns.

The suit also claims that the city’s regulations make it all but impossible for residents to keep a gun ready for immediate self defense in the home.

The Supreme Court struck down Washington’s handgun ban June 26. The D.C. Council passed emergency legislation July 15 in an effort to comply with the court’s ruling.

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This is Part III in a series, to read this series from the beginning see: Choosing a New Gun Part 1 and Choosing a New Gun Part 2

I acquired a couple of 40 S&W caliber handguns to try out.  The first was a Springfield XD Sub Compact, the second was an H&K P2000 (standard size). Both of the guns had a good feel to them in grip and in balance.

First up was the Springfield XD 40 SC

I ran a target out the the 7 yard line and put a few test rounds through the gun.  For a target I used an Alco Transitional Target I [TRS-I US Treasury Silhouette 14" x 20" Blue], for ammunition I used CCI Blazer Brass.

Observations

The Springfield XD had no mechanical issues, fed, fired and ejected every round on cue.  The gun was very loud, most of this is due to the 3″ barrel, so be prepared for a rather loud report if you decide to shoot an XD compact.

The grip was a little short, but this was cured with the addition of a Pierce Grip.

First 9 rounds fired out of the gun put a 5″ group on the paper. (4″ group if you do not count the one flier round).

Results

I ran another hundred or so rounds through the gun to try out different drills, such as weaver, strong hand, and weak hand.  Overall the Springfield XD performed well, with the exception of the loud report.

Next up was the H&K P2000 40

I ran a target out the the 10 yard line and put a few test rounds through the gun.  For a target I used a USPSA cardboard target, for ammunition I used CCI Blazer Brass.

Observations

The HK P2000 had no mechanical issues, fed, fired and ejected every round on cue.

The grip felt a bit small in diameter, but this was cured by changing out the backstrap to the larger size.

First 12 rounds fired out of the gun put a 4″ group on the paper at 10 yds (removing the flier towards the bottom the group becomes a 3″ group).

Results

I ran another hundred or so rounds through the gun to try out different drills, such as weaver, strong hand, and weak hand.  Overall the P2000 demonstrated good performance and accuracy.

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Shooting for Lead Poisoning Even with all the education about lead-based paint, lead poisoning is still found in children. One often unrecognized source of lead is indoor shooting ranges where the air can be contaminated with lead dust.

Inhaling air containing lead dust can result in high blood lead levels. The dust can also be brought home on clothes. This can cause secondary lead poisoning, particularly in young children. The highest blood lead levels the Baltimore City Health Department ever recorded were in an attendant who regularly swept up in an amusement park shooting gallery. (http://findarticles.com/p/articles/mi_m0816/is_n10_v9/ai_6885050)

The shooting-team coach was asymptomatic for lead exposure; in January 2002, he sought BLL testing from his health-care provider after reading about potential lead exposure at firing ranges. The BLL test result of 44 µg/dL was reported to EPHP in accordance with the Alaska lead surveillance system, which requires laboratories to report all BLLs >10 µg/dL. An epidemiologic investigation by EPHP revealed that the man was the chief range officer and shooting-team coach for firing range A, which was used primarily by adolescents. In February 2002, EPHP tested BLLs for all seven members of the shooting team, who were aged 15–17 years. The mean BLL was 24.3 µg/dL (range: 21.0–31.0 µg/dL). BLLs for 14 nonshooting family members were significantly (p<0.05) lower (mean: 3.5 µg/dL; range: 1.0–7.0 µg/dL) (Table). EPHP advised parents of the team members that their children should discontinue use of the firing range.

Range A, an indoor firing range, was used by the shooting team on school property in a multipurpose building that also housed a hockey rink. A utility fan located near the bullet backstop ventilated the range; no formal range maintenance protocol was observed. An environmental evaluation performed in May 2002 by an independent environmental and engineering consulting firm concluded that the range and its ventilation system were contaminated with lead dust. Three months after their initial testing, the four shooting-team members available for retesting all had lower BLLs; their levels declined from 29 to 16 µg/dL, 23 to 11 µg/dL, 22 to 16 µg/dL, and 21 to 14 µg/dL (retest mean: 14.3 µg/dL; range: 11–16 µg/dL) (Table). Range A was closed for 1 year, during which time the building was renovated, and a new ventilation system was installed.

This study indicates the problem is not so much in the shooting activities but rather in the ventilation system of the indoor range. I checked recently with the indoor range I normally shoot at, I was glad to find out that the range has a high quality negative pressure ventilation system. This evacuates the lead dust and other contaminants to reduce ingestion.

For those who are the belt and suspenders type, you may wish to wear a particle mask. Just make sure you use a mask that will be effective. Lead dust is not mitigated with a regular particle mask, a HEPA mask required to protect against lead dust.

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