Almost a horrible Father's Day

[Slowdive]

Allow me to show off my crappy graphics skills

The bigger mg is relative to mb, the more compensation.

 

[Nicole]

Touche, it would be the mass of the gas and not the volume specifically. But obviously volume is related to mass when dealing with gas at specific pressures.

LOL, sorry, I wasn't trying to pick nits. While mass and volume are largely interchangeable for the powder, they start to quickly become different concepts when we move to the gas because the pressure & volume will change as the gun fires. I really just wanted to check if we were talking about the same thing. I know I'm missing something, but I don't know what it is. Just ruling things out as we go.

So, your graph there seems to be interesting but not to the point. I would chart grains of powder to energy of the bullet and see what that shows. I think you would get with that graph an actual "comp effectiveness" metric.

Oh I did that one too.

There's a slight loss of energy as the powder load goes down for this group of loads, but this graph doesn't control for the bullet weight. Powder charge and bullet weight don't have a direct relationship, so this graph isn't as informative as the first one. This post's graph is nothing more than a survey of what kinds of energy .500 loads create.

However, your graph does show one interesting thing. The energy is of the bullet. So if the energy goes up, more compensation is needed because the energy of the bullet is equal to the recoil energy, give or take a few issues not related to revolvers.

Agreed. The energy of the bullet comes from the powder, so if there's more energy in the bullet, there is logically equally more energy in the gas which may act on the comp to increase the compensation.

Assuming "it" is the comp, it needs some combination of volume/mass because the idea is the volume of air escaping the comp creates the downward force above the barrel to push it down.

I get the idea of how a comp works. Your explanation and Slowdive's drawing both explain the concept of a comp quite well, but I already understand that. I want to know why it doesn't work as well with heavier bullets. Jim said that as I decrease powder and increase the bullet weight, the comp's effectiveness drops. As I understand things, the energy of the gas is what works the comp (more energy = more recoil but also more energy to work the comp). My first graph shows that as I decrease powder and increase bullet weight the energy goes up, so why don't I just drive the comp harder to compensate for the heavier recoil?

Imagine a scuba tank filled with CO2 and a small CO2 canister both loaded to 1000 PSI. Now imagine cutting the top off both (assuming the resulting hole is proportional to the volume/mass of gas) at the same time. Which one has more force?

If I have 2 lbs of gas stored at 1000 PSI and 1 lb of gas stored at 1000 PSI, then there's more energy in the 2lbs of gas. More mass at the same pressure.

It's the mass of the gas counteracting the mass of the bullet.

Why do I need to counteract the mass of the bullet? Why is the mass of the bullet relevant beyond how it affects the pressure of the gas? The bullet didn't do anything. The gas expanded and acted on the bullet. The gas pushes the bullet forward and the gun (roughly) backward. In a handgun, the backward motion also gets translated to muzzle flip because of the geometries involved. The comp reroutes the gas (once it's done most if not all of its work on the bullet) to push the gun forward/down depending on the comp. As I understand it the gas is compensating for the gas, not the bullet.
Just to be clear, I don't doubt what you guys are saying, I'm just trying to make sense of this. Thank you!

 

[Slowdive]

Why do I need to counteract the mass of the bullet? Why is the mass of the bullet relevant beyond how it affects the pressure of the gas? The bullet didn't do anything. The gas expanded and acted on the bullet. The gas pushes the bullet forward and the gun (roughly) backward.

The bullet did do something, its a mass that was acted on by a force which created and equal and opposite force..ala Newtons laws of motion. In effect the gas pushed on the bullet and the bullet "pushed back". The heavier the bullet, the more pushing there is.

Also (this is nitpicky I know) recoil increases linearly with velocity (conservation of momentum). Energy increases non-linearly with velocity (v^2). This is an important detail because the momentum of the projectile is the same as the momentum of the gun m(bullet) * velocity(bullet) = m(gun) * velocity(gun).

This is not true of energy (unless the gun and the bullet are the same weight). The energy of the bullet is way higher because the velocity of the bullet is WAY faster than the recoil velocity of the gun.

 

[terraformer]

I get the idea of how a comp works. Your explanation and Slowdive's drawing both explain the concept of a comp quite well, but I already understand that. I want to know why it doesn't work as well with heavier bullets. Jim said that as I decrease powder and increase the bullet weight, the comp's effectiveness drops. As I understand things, the energy of the gas is what works the comp (more energy = more recoil but also more energy to work the comp). My first graph shows that as I decrease powder and increase bullet weight the energy goes up, so why don't I just drive the comp harder to compensate for the heavier recoil?

If you increase the mass of the gas in order to increase the comp's effectiveness, you would increase the pressure beyond safe limits. The pressure in the chamber is primarily a function of the amount of gas produced by the burning powder, the friction of the bullet along the walls of the chamber/barrel, the volume of the chamber/barrel and the weight of the bullet. All of this is factored in when the bullet mfg creates their reloading recipe.

It's the mass of the gas counteracting the mass of the bullet.

Why do I need to counteract the mass of the bullet? Why is the mass of the bullet relevant beyond how it affects the pressure of the gas? The bullet didn't do anything. The gas expanded and acted on the bullet. The gas pushes the bullet forward and the gun (roughly) backward. In a handgun, the backward motion also gets translated to muzzle flip because of the geometries involved. The comp reroutes the gas (once it's done most if not all of its work on the bullet) to push the gun forward/down depending on the comp. As I understand it the gas is compensating for the gas, not the bullet.
Just to be clear, I don't doubt what you guys are saying, I'm just trying to make sense of this. Thank you!

The problem is you are reading Jim's statement too literally. He simplified it but in reality, a comp (like what's found on the S&W 500*) is not counteracting the recoil of the bullet (or "the gas is compensating for the gas") but counteracting the flip of the barrel. There is some italian made revolver they manufacture and market as recoil free but in reality it is muzzle flip free. They place the barrel in line with the plane of the gun's natural recoil path when in human hands. As a result it puts the recoil straight back and eliminates the barrel flip.

In most guns the barrel is high center of the handle and so the path the gun takes in recoil, while initially straight back, ends up causing rotation of the gun because the hands of the shooter cause deflection. A comp negates the force of this rotation.

* Comps on .50 BMG rifles, AR 15s, AK47s, etc counteract different forces so the above applies to the .500 and not other comps which direct force in different directions. But the principle is the same.

 

[Slowdive]

In most guns the barrel is high center of the handle and so the path the gun takes in recoil, while initially straight back, ends up causing rotation of the gun because the hands of the shooter cause deflection. A comp negates the force of this rotation. .

The rotation is due to the fact that the bore axis is higher than the center of mass of the gun. Even with no hands the gun would rotate. If you made a gun where the Center of Mass was on the bore axis, there would be no flipping...it would recoil straight back.

 

[eisenhow]

One poster above mentioned a list of guns prone to bump fire. Where is such a list? And how does one see it?

The "list" referred to was the EOPSS list. "It contains weapons determined by Massachusetts approved independent testing laboratories to have satisfactorily completed the testing requirements of M.G.L. c. 140, § 123; clauses 18th; 19th; 20th; and 21st." NOT a list prone to bump fire

 

[EddieCoyle]

Why do I need to counteract the mass of the bullet? Why is the mass of the bullet relevant beyond how it affects the pressure of the gas? The bullet didn't do anything.

The weight of the bullet has everything to do with recoil. Your body has to resist the force of the bullet moving down the barrel. Heavier bullets generate more felt recoil. It's not the gas, and it's not the pressure.

Let's take an extreme example...

Let's say you were to make a styrofoam bullet for a .500, and use an explosive propellant that was able to generate the 60,000 PSI or so that a .500 round can produce fast enough so that it reached full pressure while the bullet was still in the barrel. You would feel almost no recoil because the gas pressure isn't pushing on anything for which your body needs to provide 'backing'.

On the other hand, if you were to take a .500 bullet and connect it with a solid rod to an engine block outside of the barrel (to simulate a really heavy bullet), and selected a powder that burned slow enough so that it wouldn't generate more than 60K PSI while the 'bullet' was still in the barrel, the recoil would literally knock you over.

 

[Nicole]

The problem is you are reading Jim's statement too literally. He simplified it but in reality, a comp (like what's found on the S&W 500*) is not counteracting the recoil of the bullet (or "the gas is compensating for the gas") but counteracting the flip of the barrel. There is some italian made revolver they manufacture and market as recoil free but in reality it is muzzle flip free. They place the barrel in line with the plane of the gun's natural recoil path when in human hands. As a result it puts the recoil straight back and eliminates the barrel flip.

That'd be the Chiappa Rhino I believe. I follow you on the recoil vs. muzzle flip thing, but my understanding is that ports/muzzle brakes/comps work on the same basic principle - redirect the gases in order to counteract whatever motion it is you wish to reduce.

The weight of the bullet has everything to do with recoil. Your body has to resist the force of the bullet moving down the barrel. Heavier bullets generate more felt recoil. It's not the gas, and it's not the pressure.

Let's take an extreme example...

Let's say you were to make a styrofoam bullet for a .500, and use an explosive propellant that was able to generate the 60,000 PSI or so that a .500 round can produce fast enough so that it reached full pressure while the bullet was still in the barrel. You would feel almost no recoil because the gas pressure isn't pushing on anything for which your body needs to provide 'backing'.

On the other hand, if you were to take a .500 bullet and connect it with a solid rod to an engine block outside of the barrel (to simulate a really heavy bullet), and selected a powder that burned slow enough so that it wouldn't generate more than 60K PSI while the 'bullet' was still in the barrel, the recoil would literally knock you over.

I'm kind of following, but I counter with a rocket engine. If it's all about the bullet, then why does a rocket engine work?

It was suggested to me that what I'm missing is that it isn't that the heavy bullet/high pressure loads won't work with a comp, it's that they won't work well with the stock .500 comp. If we took Jim's loads to a comp guy, he could design a comp that would work well for that load. This makes sense to me - particularly since .50 BMGs and even tanks have comps....obviously, SOMETHING works when you get above .500 pressures. I know very little about fluid dynamics, but it makes sense that higher pressure/velocity gas is going to interact with a comp in a different way and might require a different design to see good performance. Does this make sense to you guys?

 

[EddieCoyle]

If we took Jim's loads to a comp guy, he could design a comp that would work well for that load.

He won't be able to do a thing because no matter how you direct it, 25gr of gas isn't going counteract the recoil generated by a 700gr bullet.

You're rocket analogy is interesting, but instead of just launching a 'rocket', the gas from a comp has to reverse the direction of it. You're not going to turn around a 700gr rocket with 25gr of gas.

 

[Slowdive]

I'm kind of following, but I counter with a rocket engine. If it's all about the bullet, then why does a rocket engine work?

Your rocket engine example is a really good one.

Conservation of momentum still applies (Ma * Va = Mb * Vb), but there is a very important distinction between a rocket and a gun. A rocket is an open system, where a gun is more of a closed system. In a gun the gas and the bullet travel together and leave the muzzle at nearly the same speed (Va ~ Vb), which means for effective recoil compensation, Ma needs to be close to Mb.

A rocket engine does not have this stipulation, in fact the velocity of the gas is much faster than the rocket (the gas coming out of a large space shuttle type rocket is coming out @ almost 15,000 fps...I had to look this up). Once the rocket accelerates to a point where it is traveling fast, it doesn't work anymore. Va >>Vb and Ma<<Mb.

This makes sense to me - particularly since .50 BMGs and even tanks have comps...

A BMG uses a 225gn to 250gn powder charge. The 50 cal S&W is using only a 1/10th of that charge.

He won't be able to do a thing because no matter how you direct it, 25gr of gas isn't going counteract the recoil generated by a 700gr bullet.

This can't happen in a gun, but it could happen in a rocket. For example. If that 25gns of gas was travelling 30,000 fps, then it could probably compensate for a 700gn projectile travelling 1100 fps.

 

[Spanz]

The weight of the bullet has everything to do with recoil. Your body has to resist the force of the bullet moving down the barrel. Heavier bullets generate more felt recoil. It's not the gas, and it's not the pressure.

Let's take an extreme example...

Let's say you were to make a styrofoam bullet for a .500, and use an explosive propellant that was able to generate the 60,000 PSI or so that a .500 round can produce fast enough so that it reached full pressure while the bullet was still in the barrel. You would feel almost no recoil because the gas pressure isn't pushing on anything for which your body needs to provide 'backing'.

On the other hand, if you were to take a .500 bullet and connect it with a solid rod to an engine block outside of the barrel (to simulate a really heavy bullet), and selected a powder that burned slow enough so that it wouldn't generate more than 60K PSI while the 'bullet' was still in the barrel, the recoil would literally knock you over.

THAT makes sense!

So if porting will do nothing, how about converting it single action? Is that possible, or will that cause some other problems? If I remember the Ruger Vaquero hand grips are deliberately designed so the gun/arm rotate upwards to dissipate the recoil, but in single action.

 

[rep308]

Note to self, stick with your Model 29 .44 magnum.....

 

[TWtommers]

You guys are wicked smaht but my head hurts now.

 

[Nicole]

I think I'm wrapping my head around it now. For some reason I kept getting hung up on the energy instead of the momentum of the bullet. I must have been nodding off on momentum day back in physics class.

Slowdive, thank you for hammering away with the momentum talk. Something finally crystallized when I found a discussion elsewhere of an experiment by Hatcher. Total momentum begins at zero and must remain zero, conservation of momentum, as you said. Hatcher plugged a barrel and then fired a round (apparently he did this in a 1903 without blowing it up), and there's no recoil. Until the bullet starts moving and gains "positive" momentum, there's not going to be any "negative" momentum (i.e. recoil) to cancel it out.

So the bullet & gas start moving and whatever m*v they have is matched by the rearward m*v of the gun and shooter. When the bullet leaves the muzzle, we have chance to capture the gas and use it to counteract the rearward m*v that we perceive as recoil/muzzle flip. If we capture the gas like this, then it stops contributing to the recoil and the recoil is equal to the m*v of the bullet. But since v(bullet) and v(gas) are nearly equal, the m(gas) has to approach m(bullet) in order for the momentums to be nearly equal and for us to have a force to counter recoil with.

Right? I think I'm saying what you guys have been saying, just slightly rephrased, so I believe I've got it now. Thank you so much for keeping at this with me. Like I said, physics is not my strong suit.

Jim, you were leaving me in the dust...

It's the mass of the gas counteracting the mass of the bullet.

He won't be able to do a thing because no matter how you direct it, 25gr of gas isn't going counteract the recoil generated by a 700gr bullet.
You're not going to turn around a 700gr rocket with 25gr of gas.

You kept referencing the bullet and I wasn't making the jump from the bullet's movement to the force generated by the movement. I couldn't understand why we'd need to turn the bullet around...I was pretty sure that'd piss of the RO's something fierce. Thanks for sticking around until it clicked for me.

 

[chinalfr]

You guys are wicked smaht but my head hurts now.

Physics 101 class on sunday is hard.

 

[Acme.Armament]

You guys are wicked smaht but my head hurts now.

Physics 101 class on sunday is hard.

Try it on a Sunday morning before you have finished your first cup of COFFEE.

 

[Slowdive]

So the bullet & gas start moving and whatever m*v they have is matched by the rearward m*v of the gun and shooter. When the bullet leaves the muzzle, we have chance to capture the gas and use it to counteract the rearward m*v that we perceive as recoil/muzzle flip. If we capture the gas like this, then it stops contributing to the recoil and the recoil is equal to the m*v of the bullet. But since v(bullet) and v(gas) are nearly equal, the m(gas) has to approach m(bullet) in order for the momentums to be nearly equal and for us to have a force to counter recoil with.

Exactly

 

[twogunwilly]

Um, I'll just be over here shooting

 

[Slowdive]

Um, I'll just be over here shooting

This reminds me of that SNL skit.... George F Will Sports Machine. This is the "Throw the Ball George" moment.

http://www.hulu.com/watch/3519/saturday-night-live-george-f-wills-sports-machine

 

[EddieCoyle]

So if porting will do nothing, how about converting it single action?

There's no need for me to do that because I know how to shoot it.

 

[drgrant]

Note to self, stick with your Model 29 .44 magnum.....

If you learn how to shoot it properly it'll never double. Most mid range .500 loads are not really that bad, especially given the enormous mass of the guns. I find EC's .500s a lot easier to shoot than hot rodded .44 mags, .454 Casull's, .480 ruger, etc... those guns are "snappy" as hell.

-Mike

 

[DavidC77]

Wow, I'm glad he's OK.

The guys at S&W told us about that on the tour. He said its your finger being tossed around by the gun that you press of the second shot with out trying to do it.

Be very glad that he is OK, wow.

 

[DavidC77]

And another one:

I looked at a few of those that come up after your video, when I saw this one I said that that guy was asking for trouble shooting it one handed !!!

 

[DavidC77]

I loved shooting the 500 at the S&W Tour, ya they were lower power rounds but it was still fun, and ya I shot a few more then one round

 

[Spanz]

There's no need for me to do that because I know how to shoot it.

Yeah, at the range it is relatively easy to control it if you know the gun. I tend to use these sort of things hunting, and in the field...things happen faster. You might get a shot off and get a little sloppy with your grip.

The downside would be, if a grizzly jumped you, you might not have the chance to cock a single action, but might get a shot off with a double action. I have heard tales of hunters opening their lodge door and a griz immediatly is on them. On the other hand, you would not want to double tap when you are deep in the woods!

As far as porting, I shoot a .454 with 300 grain (yeah it is not the 700 this guy was using) and it never pulls up like this gun did. The reason I assumed was that there are 8 ports drilled pointing straight up at the end of the barrel (4 on either side of the sight blade). It makes it loud as hell, but easier to control.

 

[EddieCoyle]

Yeah, at the range it is relatively easy to control it if you know the gun. I tend to use these sort of things hunting, and in the field...things happen faster. You might get a shot off and get a little sloppy with your grip.

The downside would be, if a grizzly jumped you, you might not have the chance to cock a single action, but might get a shot off with a double action. I have heard tales of hunters opening their lodge door and a griz immediatly is on them. On the other hand, you would not want to double tap when you are deep in the woods!

As far as porting, I shoot a .454 with 300 grain (yeah it is not the 700 this guy was using) and it never pulls up like this gun did. The reason I assumed was that there are 8 ports drilled pointing straight up at the end of the barrel (4 on either side of the sight blade). It makes it loud as hell, but easier to control.

I think it's one of those things where you you've got to try it, and if you're comfortable with it, then you can use it in the field, if not; downsize. I don't find it hard to control even with the heavy bullets, but I've got a lot of time with it. With that said, I don't think "quick follow up shot" when I think about the .500.

The .500 is a lot different than a .454. I have a .460 (which is just a longer .454) and nothing I've ever shot out of it kicks like a stout .500 load.

 

[JRyan]

When I was first getting into firearms I said something to a guy in a gun shop about compensator's and recoil and he told me that they were all about muzzle flip, I took him at his word, but thanks for explaining it rocket scientists and ballistics experts of NES!

 

[Slowdive]

I think it's one of those things where you you've got to try it, and if you're comfortable with it, then you can use it in the field, if not; downsize. I don't find it hard to control even with the heavy bullets, but I've got a lot of time with it. With that said, I don't think "quick follow up shot" when I think about the .500.

The .500 is a lot different than a .454. I have a .460 (which is just a longer .454) and nothing I've ever shot out of it kicks like a stout .500 load.

How would you compare the perceived recoil to say a scandium j-frame 357? This is the only "heavy" recoiling handgun I own (or have fired). I've shot a few 158gn & 170gn full power loads out of the 13oz. gun. It took some range time to get used to, but I'm ok with it.

I know what the numbers say, the 500 has is way more free recoil, but it has a much slower recoil velocity. The grip geometries are also different. But how does it feel?

*** I know its really unlikely that a 170gn .357 is going 1000 fps out of a 1 7/8" bbl, but I was just doing a "what if"?

 

[Spanz]

well, shooting a .500 must be a real hoot. Shooting more than 12 rounds at a time out of my much smaller .454 starts to seriously damage my hand, even with some uncle mikes gloves on.

 

[EddieCoyle]

How would you compare the perceived recoil to say a scandium j-frame 357?

I'd rather shoot the .500 than full power .357s in a Scandium J-frame.

The recoil is much more manageable when you can hang onto the gun.