200 vs. 230gr .45 ACP's

[USSR]

Read it again, John.

...4-1/4" commander which shoots my 200gr. handloads about 2" low.
Gun is regulated for 230gr. ball ammo which is right on target.

Don

[JohnKSa]

Yup, you're right--I even re-read it before posting so all I can say is that I didn't read carefully enough--twice.

[polyphemus]

A revolver would do then,now your pivot point diagram applies this is because most of the the recoil force is transferred directly to the shooter.A slide's mass and other relevant factors like friction and springs contribute to dissipate the energy generated at ignition,the remaining slide momentum causes the muzzle flip at the end of the rearward travel.

If I am understanding you correctly, you are stating that the energy of recoil is "dissipated" (completely used up and gone) before the slide reaches the end of its travel and therefore recoil is not a factor in muzzle flip.

Not understanding correctly,energy is spent or consumed or dissipated by the slide overcoming inertia,obviously kinetic energy remains within to continue the rearward motion.
And finally my point has always been that if there is any muzzle rise in this case
it does not affect trajectory,OP has a short recoil operated pistol.

[USSR]

Tell you what polyphemus, I've got 2 .45 caliber short recoil operated pistols (better known as Model 1911's) and a Ransom Rest (so no shooter related errors), and I will gladly test your hypothesis when the weather breaks, IF you agree to accept the results of my testing as either validating or invalidating your theory. Deal?

Don

[polyphemus]

Tell you what polyphemus, I've got 2 .45 caliber short recoil operated pistols (better known as Model 1911's) and a Ransom Rest (so no shooter related errors), and I will gladly test your hypothesis when the weather breaks, IF you agree to accept the results of my testing as either validating or invalidating your theory. Deal?

Very generous indeed.Could you please indicate the parameters of the experiment?Be assured that I will in good faith accept the results.

[kmw1954]

That certainly was an interesting discussion.

For what it is worth when I received my first 45acp, a Witness full size, metal frame. I worked up 2 loads. Everything was the same except the powder. The bullet is a 200gr Xtreme RN and both the loads were at starting levels for powder charge. With one the powder was HP-38 and the other was AA#5.

I don't recall which was which but one load when fired at a 7yd target were all hitting at the bottom of the target the other load was center of target.

Same gun, same shooter, same distance, same bullet, different powder with clearly different results. I do also recall after moving that load up to a mid level range it also raised the POI.

[USSR]

Okay. Range will be 30 yards, any difference should show up well at that distance. Bullets will be lead since I am a caster and have several .45 caliber moulds. The light bullet will weigh 190 - 205gr, I have both a round nose and a SWC that fill that niche. The heavy bullet will weigh 220 - 235gr and will also include a SWC and a round nose that I will obtain somewhere. All bullets will be weighed and similar weights used. Probably would be best to use the same powder for both loads. Alliant lists target loads for both 200gr and 230gr lead bullets. They say 4.0gr of Bullseye behind a 200gr LSWC produces 790fps, while the same 4.0gr of Bullseye behind a 230 lead bullet produces 810fps. Seems like a reasonable test to me. What say you?

Don

[lordmorgul]

Originally Posted by polyphemus

Not understanding correctly,energy is spent or consumed or dissipated by the slide overcoming inertia,obviously kinetic energy remains within to continue the rearward motion.

And finally my point has always been that if there is any muzzle rise in this case

it does not affect trajectory,OP has a short recoil operated pistol.

It’s not possible for all the energy of recoil to be consumed in compression of the slide spring and acceleration of the slide unless the other end of the spring is fixed. Not “held by a human hand” fixed... but fixed. As in, a mass so many orders of magnitude larger that it is irrelevant that the force acting on the free end of the spring is pushing the “fixed” mass. A bullet flying forward is applying a force in a lever of your body to the earth itself. The earth is a fixed mass in that regard, you and your hand are not.


Andrew - Lancaster, CA
NRA Life Member, Calguns.net contributor, CGF / SAF / CRPA / FPC / NAGR / NRA-ILA contributor, USCCA member

[polyphemus]

What say you?

Very good,same powder and both loaded to same level muzzle energy .
The idea is to show the effect on poi all things considered.I take it you also have a chronograph,thank you for your contribution to the science of ballistics.

[74A95]

Originally Posted by USSR

Okay. Range will be 30 yards, any difference should show up well at that distance. Bullets will be lead since I am a caster and have several .45 caliber moulds. The light bullet will weigh 190 - 205gr, I have both a round nose and a SWC that fill that niche. The heavy bullet will weigh 220 - 235gr and will also include a SWC and a round nose that I will obtain somewhere. All bullets will be weighed and similar weights used. Probably would be best to use the same powder for both loads. Alliant lists target loads for both 200gr and 230gr lead bullets. They say 4.0gr of Bullseye behind a 200gr LSWC produces 790fps, while the same 4.0gr of Bullseye behind a 230 lead bullet produces 810fps. Seems like a reasonable test to me. What say you?

Don

If having the same muzzle energy is a requirement, this won't qualify as the 230 will be going a little faster and will have a lot more muzzle energy than the slower 200.

[USSR]

If having the same muzzle energy is a requirement, this won't qualify as the 230 will be going a little faster and will have a lot more muzzle energy than the slower 200.

Okay, if muzzle energy is a criteria, I can always bump the 200gr bullet load up to 4.2gr of Bullseye. And, yes, I have a chronograph.

Don

[polyphemus]

That is the idea.You get both to come out of the barrel with the same energy and while you are at it you can also run both at the same V and test the theory that the heavier one takes longer to get going so it stays longer in the barrel.
I envy you with all those toys

[Metal god]

That is the idea.You get both to come out of the barrel with the same energy and while you are at it you can also run both at the same V and test the theory that the heavier one takes longer to get going so it stays longer in the barrel.
I envy you with all those toys

How did we get to that , both coming out at the same energy ? Isn't the "debate" about point of aim and point of impact and why different weight bullets hit at different points ? Shouldn't it be , get both bullets to impact the same place and then measure energy and velocity ?

[polyphemus]

Metal,please let the man run his experiment.

[Metal god]

I thought my question was reasonable and believe you asking me to stay out of the public conversation now is rude seeing how this isn’t even your thread .

[USSR]

...you can also run both at the same V and test the theory that the heavier one takes longer to get going so it stays longer in the barrel.

No way of testing how long a bullet stays in the barrel. I will bump up the lighter load just a little, since lighter bullets typically travel at a slightly faster velocity than heavier bullets, but I am not going to go to all the trouble of trying to match energy levels. It is what it is.

Don

[reddog81]

2" at what distance and what exactly is the problem with shooting 2" low? Shooting a milder load should raise the POI up a bit, however, It doesn't really matter at all if your practice ammo is 2" low.

Fwiw the slide has to start moving rearward at the same time the bullet starts moving down the barrel. If the slide wasn't moving as the bullet is leaving the barrel the slide would never start moving. The slide only move a fraction of an inch because the slide weighs something like 40 times or more what a bullet weighs. When the bullet has moved 4 inch the slide has only moved 1/10 and inch.

[Unclenick]

Lordmogul,

The Ransom Rest has a friction pivot centered below the grip frame to allow a z-axis moment of inertia that lets the muzzle flip up.


7A95,

Same muzzle energy will guarantee the lighter bullet impacts lower as it will then have lower momentum and thus there will be lower angular momentum imparted to the upward rotation around the z-axis of the Ransom rest.

Here is how to look at it. Kinetic energy and work have the same units. Work is a force applied over a distance (the average force from pressure applied over the length of bullet base travel from the case to the muzzle). You multiply the travel distance in feet times the average pounds of force applied during that travel to get foot-pounds of work. The kinetic energy when the projectile gets free of all force on its base is that same number of foot-pounds. So energy can be looked at as stored work or the potential to give back work. Unlike momentum, there is no time or mass factor as neither of those things changes how much force you applied for what distance.

Here's what makes that useful to know. If you have the kinetic energy and you know how many feet the bullet traveled to get it, then you know what the average force on the bullet was and that's the force that was acting in the opposite direction to move the gun. Mind you, this is the average force, not the peak force, so it doesn't tell you what the peak pressure was. When you load the two bullet weights to the same kinetic energy you will know they had the same average force applied to them over the same distance. But the lighter bullet will be going faster, so it has a shorter barrel time. This means the force imparting angular momentum around the rest's moment will be applied for a shorter time, resulting in less acceleration around it. In short, the muzzle won't be rising as fast nor will it have risen as far when the lighter bullet exits.

If one is going to toy with physics, one must cultivate the habit of considering and including everything. Physics can be a little like accounting in this regard. You have to have a place for everything and not leave entries out. Indeed, when you study where all the energy in a system is going, it is called an energy audit.

Take the idea of bore friction causing a bullet to drag a gun forward. Has any gun tried to pull itself forward out of your grasp when you fired it? No. But there is friction between the bore and the bullet and the bullet is moving forward, so where does the accounting error lie that the gun not only is not dragged forward but moves backward? Here it is: Force is needed to move the bullet forward. Force is also needed to overcome bore friction. The forces acting in the gun come from gas pressure which pushes equally in all directions. So, the accounting error is in forgetting the force overcoming bore friction, just like the force accelerating the bullet base, has an equal and opposite counterforce pushing back on the breech and that cancels it out. Therefore, there is no net forward or backward motion resulting from the friction component of the forces involved.

The force that is producing the acceleration of the bullet is another matter. This is because the bullet is moving. If the bullet were stuck in the barrel, there would be no recoil because the gun would then just be a pressurized vessel and would sit there same as a sealed CO2 cartridge does. It is the equal and opposite force giving equal and opposite momentum to the gun and bullet that causes recoil. The more the bullet moves forward, the more momentum is imparted to the mass attached to the breech. It starts when the bullet moves the first thousandth of an inch and grows from there.

So, you can't just leave things out. Even the recoil spring pushing forward against the slide presents an equal and opposite pressure back on the frame. The force cocking the hammer or striker has equal and opposite push-back force.

Per Newton's third law of motion, force always comes in equal and opposite pairs, and therefore momentum is always conserved, never growing or shrinking anywhere in the universe because positive momentum is always paired with an equal and oppositely directed momentum. It's just like double-entry accounting. And force and momentum and their opposite pairs always arise simultaneously and without delay. It may not be obvious where it is, but do the books and you will find it is not hanging out in an alternate reality waiting to be reinserted into ours.

[polyphemus]

No way of testing how long a bullet stays in the barrel

That's right but if there is a discrepancy in poi's you have an effect and probably deduce a cause.
Metal
That was a lighthearted remark I regret you took it as offensive

[zeke]

Interesting experiment, and will be surprised if there is a 2 in difference in POI between 200 and 230 target loads. Maybe 1/2 to 1 inch difference. Even at 30 yards. Course have been wrong before, like plenty of times. May also depend on weight/size of 1911?

The only times have seen noticeable difference at 25 yards from moderate target loads was with heavy loaded 255 lrnfp from (high maybe 1.5 in) or a 185 plus p (low). Both from 5 in all steel 1911.

[polyphemus]

Uncle NicK
Please explain how it is that two objects with the same kinetic energy have different momentums,two simple formulas numbers don't lie

[polyphemus]

Uncle Nick
You are correct.

[polyphemus]

USSR. The numbers say same momentum higher energy for the lighter bullet,
the experiment is then only valid for equal momentum,here I was in error.

[Unclenick]

Right. Momentum is the quantity that is equal and opposite in a gun, so it is what conveys force and resulting velocity in recoil, not energy.

The classic firearms example is also in studying recoil. Many if not most folks have the idea a gun doesn't injure the shooter as much as the shootee because the contact area of the gun is bigger for the shooter. But that area difference is typically small compared to the difference in kinetic energy in the bullet and in the recoiling gun.

Example:

A 150 grain bullet is fired from a 8.5 lb rifle at 2500 ft/s. The rifle is 397 times heavier than the bullet, so, since they both have the same momentum in opposite directions, the final velocity of the rifle 397 times smaller than the bullet velocity, or 6.3 ft/s. When you calculate the kinetic energy, you first convert the weights of the bullet and gun to slugs of mass:

Grains/225218=slugs¹, and pounds/32.17405=slugs, so

150 grn/225218 grn/slug =0.00066602 slugs
8.5 lb/32.174 lb/slug = 0.2642 slugs

KE = ½mV²
KE of bullet = 0.5 × 0.0006602 × 2500 × 2500 = 2081 ft-lb
KE of rifle recoil = 0.5 × 0.2642 × 6.3 × 6.3 = 5.24 ft-lb

5.24/2081=0.00252

So, the shooter gets hit with 0.00252 times the energy the shootee does. Additionally, if you suppose the contact area of the butt of the rifle is 2 square inches and the bullet cross-section is .0745 in², there is about 27 times more area on the shooter absorbing the blow, but it is that huge difference in KE, the measure of work the recoiling gun can do on the shooter, that accounts for most of the shooter's relative comfort. So, the fact the gun weighs more than the bullet is the source of protection.

In 1720 Willem 's Gravesande dropped different brass balls into clay and discovered that when he doubled the drop hight the ball penetrated 4 times as far. As s student of Newton's work, he realized that because gravity is an accelerating frame of reference, the balls dropped from twice the height were going twice as fast. But since they penetrated four times as far, the penetration of clay was therefore proportional to the square of velocity. Kinetic energy is also proportional to the square of velocity, and even though it wasn't defined clearly until almost a century later, this is the historical root of its role in terminal ballistics.

Of course, 's Gravesande was working with relatively slow velocities. When energy is conveyed at high velocities, because it is a scalar quantity not tied to any particular direction as a vector quantity like momentum is, the work can go not only into penetration but into spreading a shock wave transversely and that confuses its role and merit in terminal ballistics. But overall, if two bullets of the same type and construction have the same kinetic energy, the one that has the greater momentum will penetrate ballistic gelatin further. There are a lot of examples of this comparing 9 mm and 45 Auto. But get into penetrating hard barriers and the roles can reverse, the difference being in how fast energy must convert to work to break through them.

¹Pounds × 7000 equals grains, and 7000 × 32.174 = 225218

[TX Nimrod]

But, no matter what measurement is used, the 3rd Law prevails. Equal and opposite, no matter if it’s ft/lbs, lbs/ft, joules, newtons or kips.


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