Pressure as it relates to different bullet weights?

[Changeling]

When you are shooting 2 different bullet weights in the same caliber, in this question a 45 caliber in 266 gr vs a 300 gr, and the pressure is relatively the same, is the recoil relatively the same, I'm confused here! Thanks for the help.

[gray wolf]

I believe you asked about recoil, I would look at bullet velocity.
If a heavy bullet is driven to the same Vel. as a lighter bullet, the recoil should be more for the heavier bullet. If you slow down the bigger slug recoil should be less.
Perhaps someone can add how the pressure relates to this.
It is my belief that guns of different caliber operate at different chamber pressure.
Lets say the operating chamber pressure for a given firearm is 40,000 psi, That is the max for that gun. You can load a 200 grain bullet below that and up to the max of 40,000.
Now you go to a 275 grain bullet, the operating max pressure will still be 40,000 for that gun and that Caliber.
You can go below and up to the 40,000 the same as with the lighter bullet.
The recoil will be more with the bigger bullet.
Yes you may get less recoil if you load the bigger bullet very, very light.
More pressure most of the time means more velocity, more speed = more recoil.
That's the best I can do with this one. We have some ballistic people on the forum who will get technical and give you the classroom version.

I just re read your question---no the heavy bullet will have more recoil.

[fredj338]

The loads pressure really has nothing to do with recoil. You can drive that 266gr bullet at 1200fps w/ 25Kpsi or 40Kpsi w/ near identical recoil, but nearly double the pressure by using a faster, higher energy powder. Longer heavier bullets increase pressures using the same powder so a 300gr will need less powder to reach the same pressure as the 266gr. The 266gr being lighter, will likwly go faster. How much faster determines felt recoil.
As GW notes, recoil is a product of bullet wt x vel so a 266gr bullet @ 1200fps would have sim recoil to a 300gr @ 1125fps or so. Again, pressure has nothing to do with felt recoil.

[lwknight]

The difference between 300 and 266 grains is not enough to make a big difference in recoil.
As for pressure. Who published the info? (retorcally) Sometimes a powder or bullet manufacturer does not retest old loads with the same equipment that new loads are tested with so its possible to get overlapping info.

[rob45]

Have you tried plugging some figures into a recoil calculator?

The formula will require:
1. Gun weight
2. Weight of bullet
3. Velocity of bullet (at the muzzle).
4. Weight of powder charge.

Obviously you want to keep the gun weight the same for your theoretical comparison.
The formula will calculate both recoil force and recoil speed.

Doing this may help you to decide if there is any significant difference.

[RobS]

Changeling:

I've been looking at a variety of loads here in the Lyman Reloading manual and as this book is laid out there are many cartridges that have different bullet weights ranging from light bullets to heavy bullets for a designated caliber. Also noted is that the starting or minium loads the pressures for both the light loads and the heavy loads is about the same.

I'll use for example the 454 Casull simply because it is already opened to the page and because it has a good variable in bullet weight. A 225 grain and a 300 grain bullet using the starting loads of Unique powder for both (225g with 12.7g of Unique & 300g with 10.5g of Unique) have a CUP pressure 20,100 (225g bullet) and 19,300 (300g bullet) respectively. Since the pressures are similar with the same powder given then it is a normal pattern that the lighter bullet travels faster than the heavier 1,348 fps vs 1,049fps.

With this the recoil will be about the same regarding recoil energy (ft/lbs) 13.92 for the light bullet and 14.00 for the heavy as they have different velocities. Take the same bullets and run them the same velocities and there will be a definate difference in recoil and a noteable difference in CUP pressure. Although I do have to say that the felt recoil is different IMO. The light bullet gives to me a snappy bite vs the heavy which feels more like a backward push in this caliber. I used a free program called Point Blank to compute the recoil energy for this example. Point Blank is a software program a person can find on the web with a simple google search or here is a link http://www.stevespages.com/page8b.htm
just scroll down until you find Point Blank shooting software.

[atr]

force = mass x velocity

the "force" or recoil is a function of the mass of the bullet times its velocity ,,,

[RobS]

force = mass x velocity

the "force" or recoil is a function of the mass of the bullet times its velocity ,,,

Correct...........+1

[Rocky Raab]

Not to throw a clinker here, but we perceive noise/blast to be part of recoil. If you ask people to shoot two loads (one high pressure and the other low) that propel the same bullet with the same velocity from the same gun, 90% of those shooters will say the high-pressure load "kicks" harder.

Pressure creates that blast, and so we "feel" more recoil with higher pressure loads, even if the bullet/velocity numbers are equal. (There is actually a small increase in real recoil due to a "jet effect" in high pressure loads, but that only confuses the issue.)

[Marlin Hunter]

Originally Posted by atr View Post
force = mass x velocity

the "force" or recoil is a function of the mass of the bullet times its velocity ,,,

Correct...........+1



I thought it was mass and rate of change in velocity.

Isn't recoil = force over a period of time?

Same force over a shorter time (impulse?) gives more recoil.

[felix]

MH is correct. The other posts are incorrect as it pertains to this relationship. Rate of the velocity's change is the acelleration of the projectile by definition. ... felix

[lwknight]

The percieved rercoil will vary by the way that a shooter holds the gun and his own body mass will effect the perception of said recoil. It would not work out accurately to use the recoil table to campare effects on 2 different shooters on linear scale. Or not within reasonable limits anyway. Since perception of recoil is a human factor the arguement of which kicks harder will be debated forever.
A person with large heavy arms will recieve more pressure in his hand than a person of lighter stature that can distribute the energy to a longer distance.

Combat shootinger need a quick second shot and might consider a heavy recoil to be anything that takes the gun off target by a given amount and a target shooter will be only concerned with how much the gun hurts his hand. So the frame of mind between two shooters can affect the perception of recoil as well.

[Changeling]

I thought it was mass and rate of change in velocity.

Isn't recoil = force over a period of time?

Same force over a shorter time (impulse?) gives more recoil.


Confusing subject, wouldn't force be the same as "pressure" over a given time then, since the pressure is the force?


My thanks to everyone regarding this subject. Thanks for the link Robs.

[geargnasher]

For those with enquiring minds or who are needing a sure cure for that late-night insomnia, here's my take on it:

Force generally is figured in one direction, or as a vector, as in recoil force. Pressure within a closed system acts in all directions equally (Pascal's law). The pressure from the burning powder itself generates virtually no recoil except that from muzzle blast (jet engine effect). The actual recoil force in question is determined principally by two things: The mass of the objects being acted upon, and the rate of acceleration from rest of the objects in the system. All three of Newton's laws of mechanics are in effect here: First you hold the gun. Everything is still and wants to stay still. Then you fire the gun, creating motion from a standing start of the boolit, which accelerates at a certain rate depending upon the pressure curve of the burning powder as the boolit travels down the barrel, boolit weight, frictional forces, grip force, and a thousand other things. (F=Ma here, where acceleration is a derivative of velocity). Then, as the boolit overcomes static enertia, moves and begins to accelerate down the bore and out of the gun, Newton's third law takes effect. The gun and what is touching it applies force in the opposite direction of the boolit's travel in an amount exactly equal to the force applied by the boolit. So if your boolit is developing 300 ft/lbs of energy at an instantaneous muzzle velocity then the gun and your body are responsible for absorbing that much recoil energy. The only reason it is possible for a human to physically contain that kind of energy is that the mass of the gun and your arms is much more than the boolit and that mass soaks up a lot of force, plus it is a factor of TIME. Try throwing a bowling ball versus a marble, same principle.

Keep in mind that just figuring velocity and mass only gives you instantaneous force, not force over time, as in acceleration/deceleration. Velocity is linear, a first derivative. The second derivative of velocity is acceration, which is almost never exactly constant in the real world due to various frictional counter forces, but is rather an arc or curve, sometimes with woops and bumps. The "force" is the area under the acceration/mass curve, or the slope of the line at any given velocity point on that curve.

If you want to know actual recoil force, figure exact velocity at the muzzle, mass of the boolit, and length of the barrel, assume that the acceleration is linear (which is most probably is not, but close enough). Derive rate of acceleration from rest using muzzle velocity, barrel length to make it a function of time, and then plug into Newton's F=Ma formula. That gets you FORCE in whatever units you're using. compare that force substituting different values for boolit mass and muzzle velocity to figure how it affects actual recoil energy.

Gear

[OLPDon]

Gear:
Now that is a outstanding take on recoil quite a dissertation.... And a good read as well.

(the only thing I could add) is flinch factor: for most, if it the report is larger (bigger Bang) the brain precives larger recoil. I live in a large City with that being said, hearing screaching tires I expect that crunch after. Without the crunch I found myself eye sqinting waiting to hear the crash that didn't happen. We all have different perceived expectations.
Granted if one shoots a 44 mag. top end we all have the same effect :holysheep. Before the shot and after.
Don

[Changeling]

Very interesting Gear, thank you for the information.

[cptinjeff]

[QUOTE=Rocky Raab;812810]Not to throw a clinker here, but we perceive noise/blast to be part of recoil. If you ask people to shoot two loads (one high pressure and the other low) that propel the same bullet with the same velocity from the same gun, 90% of those shooters will say the high-pressure load "kicks" harder.

This is a point not to be missed. One reason a heavy slow .45 colt can be more pleasant to shoot than a .357 or .44 mag.

ONE EASY cure for someone having "the flinch" is to double up on hearing protection....(foam plugs with muffs over top). I always sugest this when teaching someone to shoot a heavier than they are used to load. It is amazing how people can settle down when the percussion is percieved to be lessoned. If I'm shooting a blaster like a .454 I wear the disposable plugs with electronic muffs over the top so I can still hear conversation. A .45 at moderate velocities has less "concusion" with more force (recoil) than a full bore .357 and many will shoot the .45 better.

My opinion only...jb

[yondering]

Not to throw a clinker here, but we perceive noise/blast to be part of recoil. If you ask people to shoot two loads (one high pressure and the other low) that propel the same bullet with the same velocity from the same gun, 90% of those shooters will say the high-pressure load "kicks" harder.

Pressure creates that blast, and so we "feel" more recoil with higher pressure loads, even if the bullet/velocity numbers are equal. (There is actually a small increase in real recoil due to a "jet effect" in high pressure loads, but that only confuses the issue.)

Rocky, that isn't the whole story either, and is only half right. Noise and blast have just as much to do with powder type and burn rate, or more, than with pressure. A fast powder, like Bullseye, and a slow powder, like H110, can easily be loaded to the same pressure, with the same bullet weight. Guess which one will have more blast?

Personally I think the OP could be answered more correctly by going outside and actually shooting a few loads, than discussing it on the internet.

[geargnasher]

I believe the OP was looking to improve his understanding of interior ballistics, not work out his "forearm chronograph". Anybody can load test rounds and go blaze, but understanding what's going on is nice too.

Gear