1911Tuner
Moderator Emeritus
Hi Peter, and thanks for using that approach...the scientific one.
The ejecta is the sum of bullet mass and that of the particulate in the gasses and smoke from the burned powder. The mass of those gasses is nearly the same as that of the unburned powder...so there is a recoil impulse after the bullet exits. It's just too small to detect during the cycle of the gun. Figuring a typical 5-grain charge at about the speed of sound...say a thousand fps here to keep it simple...and ignoring the blowby gasses that escape past the bullet
at the instant of ignition...that impulse would be roughly 1/8th that of a .22 Short fired from a 2.5 pound pistol. Pretty insignifigant, but still part of the whole. With bottleneck rifle calibers, you have a little different set of dynamics at work, but that's meat for another discussion.
The nominal .45 ACP bore diameter is .451 inch. Land diameter is .005-.007 inch smaller, depending on the barrel manufacturer. Nominal bullet diameter is .451 inch. Assuming nominal dimensions, even a non-rifled bore would present a good bit of resistance to the bullet, since the plug is the same size as the hole.
Of course, bullet material is also a factor. Harder jacket alloys offer more resistance, as do harder lead cores. Lead bullets offer less for a given diameter...but alloy also is a factor. Some lead alloys are harder than others.
A basic rule of thumb is that lead bullets need to be sized to .001 inch larger than bore diameter for best performance. I size my cast bullets to .452 inch.
For your calculations, you'll need to weigh a slide, a barrel, and a bullet to determine the ratio. For all practical purposes, 40:1 will do.
Yep. It doesn't matter whether the gun is a semi-auto or a musket. Force forward is force backward. The semi-auto's design simply spreads the recoil impulse out over a longer time and distance. That's why a self loading shotgun's recoil is more like a hard shove, while a pump of equal mass is a sharper punch.
Oh...One more thing for Grump. You have to grip the rope a distance from the end, or you probably won't see it.
Think about that statement, John...and you're partially correct...but you're ignoring the fact that there still has to be an opposing force that is driving the frame away from the bullet in order to cause a tensile stress on the topstrap. Otherwise, the gun would pitch forward. There can't be one force in one direction. Force forward...Force backward. Remember?
Where you scored is...The most resistance is offered at the inception of bullet acceleration...within the first half-inch or so. Objects at rest and all. The same goes for trying to force a plug into a hole that's smaller than the plug. The harder and faster you push...the harder it resists.
Which reminds me...
Peter. One other thing. The contact resistance between bullet and barrel isn't constant. It's much greater at the very beginning, when the bullet hits the hard resistance in the leade...before it gets started into the rifling. Always harder to get an object moving than it is to keep it moving. That's why pressure peaks early and fast, and that's where 90% of the punch is delivered to the breechblock and locking lugs.
As the bullete accelerates, pressure also drops fast. There are two things at work here. The faster it's moving, the less force it takes to keep it moving...and to accelerate it. Since force forward=force backward...the force against the lugs also drops off.
And...Because the volume of the cylinder behind the bullet is increasing. So...The forces at work are sudden and high at the start...and diminish as the bullet moves.
The ejecta is the sum of bullet mass and that of the particulate in the gasses and smoke from the burned powder. The mass of those gasses is nearly the same as that of the unburned powder...so there is a recoil impulse after the bullet exits. It's just too small to detect during the cycle of the gun. Figuring a typical 5-grain charge at about the speed of sound...say a thousand fps here to keep it simple...and ignoring the blowby gasses that escape past the bullet
at the instant of ignition...that impulse would be roughly 1/8th that of a .22 Short fired from a 2.5 pound pistol. Pretty insignifigant, but still part of the whole. With bottleneck rifle calibers, you have a little different set of dynamics at work, but that's meat for another discussion.
The nominal .45 ACP bore diameter is .451 inch. Land diameter is .005-.007 inch smaller, depending on the barrel manufacturer. Nominal bullet diameter is .451 inch. Assuming nominal dimensions, even a non-rifled bore would present a good bit of resistance to the bullet, since the plug is the same size as the hole.
Of course, bullet material is also a factor. Harder jacket alloys offer more resistance, as do harder lead cores. Lead bullets offer less for a given diameter...but alloy also is a factor. Some lead alloys are harder than others.
A basic rule of thumb is that lead bullets need to be sized to .001 inch larger than bore diameter for best performance. I size my cast bullets to .452 inch.
For your calculations, you'll need to weigh a slide, a barrel, and a bullet to determine the ratio. For all practical purposes, 40:1 will do.
Yep. It doesn't matter whether the gun is a semi-auto or a musket. Force forward is force backward. The semi-auto's design simply spreads the recoil impulse out over a longer time and distance. That's why a self loading shotgun's recoil is more like a hard shove, while a pump of equal mass is a sharper punch.
Oh...One more thing for Grump. You have to grip the rope a distance from the end, or you probably won't see it.
Think about that statement, John...and you're partially correct...but you're ignoring the fact that there still has to be an opposing force that is driving the frame away from the bullet in order to cause a tensile stress on the topstrap. Otherwise, the gun would pitch forward. There can't be one force in one direction. Force forward...Force backward. Remember?
Where you scored is...The most resistance is offered at the inception of bullet acceleration...within the first half-inch or so. Objects at rest and all. The same goes for trying to force a plug into a hole that's smaller than the plug. The harder and faster you push...the harder it resists.
Which reminds me...
Peter. One other thing. The contact resistance between bullet and barrel isn't constant. It's much greater at the very beginning, when the bullet hits the hard resistance in the leade...before it gets started into the rifling. Always harder to get an object moving than it is to keep it moving. That's why pressure peaks early and fast, and that's where 90% of the punch is delivered to the breechblock and locking lugs.
As the bullete accelerates, pressure also drops fast. There are two things at work here. The faster it's moving, the less force it takes to keep it moving...and to accelerate it. Since force forward=force backward...the force against the lugs also drops off.
And...Because the volume of the cylinder behind the bullet is increasing. So...The forces at work are sudden and high at the start...and diminish as the bullet moves.
