is .357 mag the best defense round?

[CrawfishTails]

Originally Posted By: Robenstein
Powders progressively burn and the longer the barrel(as long as the powder is still burning) the more it builds gas pressure which accelerates the bullet to higher velocities. That creates more kinetic energy. That is simple physics. Mass x velocity = force. You can easily see it if you compare the stated numbers for the 5.56 NATO round in 20 inch barreled M16's vs the 16 inch M4 as a great example of how just chopping a barrel down can effect performance.


I can tell you're not an engineer or scientist. Mass x velocity = momentum (not force). You're close though. Mass x (delta velocity)/(delta T) = Force, where delta velocity is a change in velocity over time. dv/dt (Unless Isaac Newton was wrong.)

 

[Mystic]

Originally Posted By: ZeeOSix
Originally Posted By: CT8
The muzzle energy seems to be a B.S. number.Figures lie and liars figure. Every action has a equal and opposite reaction ??? A bullet with 800 lb ft of energy should kncsk the shooter on his behind if the numbers were so.


Maybe it would if shot at 1 inch away, and all the energy was instantly dumped into the target.

The muzzle energy is a simple calculation based on bullet mass and velocity.




CT8, I have shot a lot of guns, including four .44 magnum revolvers. I have not been knocked down yet.

 

[Astro14]

Originally Posted By: CrawfishTails
Originally Posted By: Robenstein
Powders progressively burn and the longer the barrel(as long as the powder is still burning) the more it builds gas pressure which accelerates the bullet to higher velocities. That creates more kinetic energy. That is simple physics. Mass x velocity = force. You can easily see it if you compare the stated numbers for the 5.56 NATO round in 20 inch barreled M16's vs the 16 inch M4 as a great example of how just chopping a barrel down can effect performance.


I can tell you're not an engineer or scientist. Mass x velocity = momentum (not force). You're close though. Mass x (delta velocity)/(delta T) = Force, where delta velocity is a change in velocity over time. dv/dt (Unless Isaac Newton was wrong.)


Pretty clear from this post

Originally Posted By: CrawfishTails


You just re-wrote the laws of physics. Are you saying a longer barrel is more efficient at extracting the energy from the powder?
Energy comes from the exploding powder inside the shell, not barrel length.
You might be referring to the concentration of energy exchange as it strikes the target, a smaller barrel having a wider and less concentrated blast pattern.


that you're not one either, CrawfishTails. I wouldn't be casting aspersions.

You neglected to consider the difference in velocity created by the difference in the time over which the force of expanding gas acts on the projectile in different barrel lengths.

 

[totegoat]

My shade-tree research shows a .357 fired from an 8" barrel will penetrate any media deeper than a .357 fired from a 2" barrel.

12 ga bird shot from a 30" barrel will go clean through a can at 60 yards, maybe further.

 

[Robenstein]

Not an engineer or scientist....just a history professor. I do however know how gunpowder works. And yes, I goofed and should have said Mass x acceleration= force. Pardon my use of a similar word in the wrong place.

And btw...Newton was wrong on quite a few things(aside from using mercury as a medicine)...just ask Einstein.

 

[Astro14]

However, Newton revolutionized thought, physics, and mathematics and his work is perfectly accurate at the velocities at which firearms operate.

The history of science, that intersection of science and history, is the history of thought and it shaped the history of the world. It's also a bit of a hobby of minde, in addition to a few college classes in the history of science, I've read dozens and dozens of books on the subject....

So, Robenstein, you and I share more than just an interest in oil, or firearms...

 

[Robenstein]

Yes we do sir. I actually took a field exam in the history of technology and was a TA for a couple history of science classes at Iowa State University back in my student days. As for guns, I did give a paper on the small caliber high velocity concept at a conference back in 2008. Not on the science of it so much as how it was tested and fought by the upper brass in the U.S. Army Ordnance department in the 1950's.

And yes Newton changed the way in which we understood the universe in several areas. Amazing that he spent only about 20% of his time on science and 80 percent on alchemy or religious studies. He was indeed a bit of a mad genius.

 

[hatt]

Oh wow. We have a scientist who doesn't know a longer barrel will tend to give more velocity than a shorter barrel. Da ednmacation system dees days.

 

[ZeeOSix]

LOL, any engineer should know that the burning and expanding gasses from the gun powder burning in the barrel is what accelerates the bullet. The more efficiently the gun powder burns (ie, it all burns to contribute to the max possible bullet acceleration), then the faster the bullet leaves the muzzle, and the higher the energy in that bullet is. Kind of like "low tech rocket science".

 

[hatt]

Even if the powder burned up instantly, or within the length of a short barrel, a longer barrel(within reason) would expose the bullet to the high pressure side for a longer period of time, leading to a faster speed. I don't know the scientific explanation.

 

[ZeeOSix]

Originally Posted By: hatt
Even if the powder burned up instantly, or within the length of a short barrel, a longer barrel(within reason) would expose the bullet to the high pressure side for a longer period of time, leading to a faster speed. I don't know the scientific explanation.


True ... think of it as "time period of acceleration". The longer the bullet is exposed to the acceleration force (gas pressure in the barrel), the faster it will be coming out of the muzzle. Once the force behind the bullet goes to zero right after the bullet leaves the muzzle, the acceleration is over and the deceleration starts due to air friction.

 

[hatt]

The bullet needs enough pressure behind it to continue to overcome the resistance of the barrel. As an example, some weak .38 will actually be slower than a handgun when fired from a rifle.

 

[ZeeOSix]

^^^ Of course. A barrel could actually be too long and reduce the exit velocity. Every bullet and powered load load combination has an "ideal" barrel length for maximum muzzle velocity.

 

[CT8]

This is not backyard or Youtube wanna be actors test Bullet test.

 

[NateDN10]

And for those of you who missed the Ballistics By The Inch link that CT8 posted, here's a graph of some various .357 Magnum cartridges vs. barrel length (credit for the graph is BBTI, not me).

 

[bubbatime]

Is .357 mag the best defense round?

Well, no. A 12 gauge shotgun is generally considered the most powerful weapon a civilian can wield for self defense. It is very effective in most cases.

Then you have to factor in the possibility that the attacker(s) might be wearing body armor. And the fact that there could be numerous attackers. Some home invasions have as many as 4 or 6 attackers. Shotguns are ineffective against body armor, so in this scenario you would want a high capacity carbine that shoots rifle rounds.

In fact, a lot can be said that a rifle round (5.56, 7.62x39, .300 blackout, .308 etc) from a high capacity carbine would be the best defensive round.

For this reason, I keep an AR-15 carbine and a Remington 870P next to the bed. In a moments notice I can grab whichever one I want to.

If we are talking pistols only, then .45ACP, .357 Sig, .40SW, 9MM, .357 Magnum, and .38 Special all perform similarly when loaded with top loadings in their respective caliber.

Self defense is a software (mindset) issue, not a hardware issue.

 

[zerosoma]

Revolvers are nice to have for simplicity, but single stack 9 is where it is at, IMO. Shield, carry every day and shoot often. Has never had a failure.

 

[Mystic]

Yes, I like my S&W M&P 9mm. Instead of buying more handguns I will probably buy a .270 rifle someday, and a 12 gauge pump action shotgun. I would not mind having an AR-15 but they are expensive.

The strange thing is even though I am an old guy I have only limited experience with revolvers. I have shot a couple of small lightweight .38s, some .357 magnums, a .45 single action revolver, and 4 44 magnums. But I have never owned a revolver. And I have never owned a 1911 .45 either although I have shot 1911 .45s. If I was going to get a .45 I guess I would buy a S&W M&P .45.

 

[Olas]

It depends who/what you are defending,maunder what,circumstance.

A SPAS 15 can be very effective in CQ, a AR or AK give you more range if the terrain dictactes is, but when subtlety asks for,your discretion, a walther ppk or glock 20 are quite easy to miss.

Its about picking the tool for the job

 

[bubbatime]

Originally Posted By: Mystic
I would not mind having an AR-15 but they are expensive.


Now is the time to buy. They have never been cheaper than they are RIGHT now. You can get an AR-15 for less than $450 nowadays.

Here is an AR-15 rifle kit for $359. Add a $49 AR lower and you have a complete rifle for $410 plus shipping.

http://palmettostatearmory.com/index.php/ptac-16-m4-5-56-nato-slick-side-1-9-rifle-kit.html

Add one of these lowers for less than $50 and be done.

http://www.aimsurplus.com/product.aspx?i...amp;groupid=577

http://www.aimsurplus.com/product.aspx?i...amp;groupid=577