chamber pressure/ recoil question

[SCMtns]

My buddy and I -- both handloaders, both revolver fans-- were trying to figure something out. We both like the .45 Colt for its ability to push an even bigger and heavier bullet than the .44 Mag at roughly the same velocity but at considerably lower chamber pressures.

So here's a physics question for you: let's say a .44 and a .45 Colt both fire a 300-grain bullet at, say, 1300 fps with however many grains of the same kind of powder it would take to do that in either one. Would the .44 still have a higher felt recoil? That is, does its higher chamber pressure translate into more foot-pounds of kick, or just a different kind of recoil (hard snap vs. slow push)?

Presumably, it would take two revolvers of the same model and barrel length being fired back-to-back to test it empirically, like an SRH in .44 and another in .454. We're both aware that .44 is generally a higher-velocity round than .45 Colt +P, but if a handloader is working up a load for a particular bullet weight at a particular velocity, is lower recoil still a valid reason to go with the .45 Colt over the .44? If this is a stupid question and belies a fundamental lack of understanding of how things work, then please enlighten me.

Thanks.

[Vern Humphrey]

let's say a .44 and a .45 Colt both fire a 300-grain bullet at, say, 1300 fps with however many grains of the same kind of powder it would take to do that in either one. Would the .44 still have a higher felt recoil?

"Felt recoil" or "perceived recoil" is how the recoil feels to the shooter. Some guns, with proper designed stocks and so on, have less perceived recoil than identical guns with different stocks firing the same cartridge.

Actual recoil is determined by a basically simple formula:

M1 X V1 = M2 X V2

Where M1 and M2 are respectively the mass of the ejecta (powder and bullet) and the weight of the gun. V1 and V2 are respectively the velocity of the ejecta and the recoil velocity of the gun. (Note this formula says nothing at all about chamber pressure.)

Given a pair of identical guns, one in .44 magnum and one in .45 Colt, with the same weight bullet, same weight powder charge and same muzzle velocity, they will have the same actual recoil.

In practice, however, the guns will not be identical. The .44 Magnum will weight slightly more, because the bore and chambers are smaller, leaving more metal in the gun. So the actual recoil of the .44 will be slightly less than that of the .45.

[belus]

I could be swayed to believe that lower pressures yield less recoil. Right now I'm simply inclined to believe that is true.

It's difficult for me to discount the nozzle effect of the muzzle, wherein the barrel acts like a rocket propelling the excess powder and gas forward and driving the gun back into your hand. The diffusion and disruption of this thrust by a muzzle break is what makes them effective, no?

[Loosedhorse]

.44 will be slightly less than that of the .45.

Yeah, sorta-kinda.

There's the question of impulse. If I slow a car down from 50 mph to zero in one minute, I have lost the same amount of energy and momentum as if I did it in 5 seconds. But it's going to be a lot more memorable if I do it in 5 seconds.

Similarly, with lower chamber pressure (slower powder), the .45 bullet begins its movement more gently, compared to a more sudden acceleration of the .44 at higher pressure (with faster powder). So I think you're more likely to perceive the .45 recoil as a "push" and the .44 as a "jerk."

There are so many factors that go into perceived recoil. But if more of the total recoil is delivered early, it's likely to be noticeably "snappier."

BTW, the Model 25 .45 Colt Mountan Gun weighted 39.2 ounces, the 629 .44 weighed 39.5.

[jklinstein]

Vern nailed it. IF you load both cartridges to deliver the same sized bullet, at the same velocity, from the end of the same length barrel, with the same model/size of gun, the end effect will be nearly identical. If you load up one with higher pressure it will deliver the bullet at higher velocity, which is not what was asked.

[Old Grump]

A factor not being taken into consideration is the apples to oranges one. Just because both revolvers of equivalent mass are firing equal charges of powder and equal weight bullets they are not equivalent. .162 vs .145 (rounded off) area on the base of the bullet. Then there is the difference in volume of the 2 cases so the 44 is going to reach a higher pressure peak faster but have less surface area to push against. Advantage goes to the 45 and the recoil will be felt more in the 44.

[Jim March]

Vern nailed it. IF you load both cartridges to deliver the same sized bullet, at the same velocity, from the end of the same length barrel, with the same model/size of gun, the end effect will be nearly identical.

We're dancing around an intangible issue.

Yes, two guns both flinging, say, 300gr downrange at 1,300fps will have the same recoil assuming the guns weigh about the same.

However, if one is getting there with 24,000psi while the other is hitting 34,000psi, the difference is that the lower-pressure setup is spreading the force applied to the bullet over a broader range of time. We're talking about very small periods of time(!) but it still makes a difference in how you feel that recoil. The high-pressure load will feel more like a "slap", the low-pressure load more like a big fat "push".

Note the phrase "more like" - it may be hard or even impossible to notice the difference for some people or if the gun is very light. But it will generally make at least some difference even though the net energy transmitted to your hand is the same either way.

Pressure can affect how you perceive recoil.

Bullet weight and speed (energy) determines recoil energy. Except that you also feel a difference if two loads have the same energy, but one gets there "fast and light" ad the other "slow and heavy".

[SCMtns]

Well, my thanks to all who replied. Interesting stuff. Y'all convinced me that the total foot pounds of recoil would be the same between the two-- perhaps even slightly less from the .44, with its smaller holes and greater mass-- but there will still be a difference in "perceived" recoil owing to the different pressure curves.

Over the years, I'd finally gotten accustomed to shooting .44 Magnum without being bothered by the recoil, but then I bought my first .454, which in turn exposed me to the .45 Colt, which singlehandedly got me into handloading. I was never able to push a 300-grain hardcast out of a .44 without feeling like I'd just slammed my hand into a brick wall, but the 325-grainers I've loaded up for the .45 Colt have been downright pleasant to shoot. I guess that's why my buddy and I were wondering if lower chamber pressures somehow figured into the total foot pounds of push the shooter experiences from a revolver. I knew all I'd have to do was ask THR! Thanks again.

[Vern Humphrey]

It's difficult for me to discount the nozzle effect of the muzzle

There is no nozzle effect of the muzzle. To understand this take your hose and screw the nozzle down to a pencil-sized stream of water and put it on the ground -- it will move around from the nozzle effect.

Now take the nozzle off, and with the water turned full on, put the hose on the ground. Notice the difference?

There is no nozzle or venturi at the muzzle of your gun. Therefore recoil is simply M1 X V1 = M2 X V2.

[1911Tuner]

Vern...You've got your work cut out for ya. Good luck.

I started to say outta this one...but in the interest of science, I'll interject a little somethin' for everybody to chew on and hopefully draw the right conclusion.

Let's ignore pressure arguments for a minute and think about it in purely physical terms.

First...Understand that the bulk of what we know as recoil in a revolver occurs within the first half-inch of bullet travel because that's where the peak force occurs...at the point of peak pressure.

Study this long and hard:

Force forward equals force backward. Whatever force is required to accelerate the bullet to X velocity is "felt" by the breechblock. If a 250-grain bullet requires X units of force to acelerate it to Y fps...the chamber pressure can be anything that it wants to be. If bullet A requires ABC pounds per square inch in order to generate X units of force, and bullet B requires CDE pounds per square inch to generate X units of force...then that's what will happen...and the recoil measured in ft.lbs will be the same...regardless of the differences in chamber pressure.

This is assuming equal gun mass. If the two guns have different grip shapes, you...the shooter...will feel it differently...but the actual recoil energy will be the same.

[Gary A]

I believe what I'm going to say/ask is appropriately related to this thread but, if not, my apologies. This seems to me to be directly related to the various discussions about using something like Buffalo Bore standard pressure .38s in older alloy J-frames. We know that plus P is not going to "blow up" the cylinders in these guns. The caveat against using plus P loads in them was the potential for loosening the gun, quickly or slowly, and the possibility of stretching the aluminum top strap over time which would both loosen the gun and possibly eventually result in light hammer strikes, ultimately resulting in a useless revolver. Wouldn't such an occurrence be caused (if at all) by the situation described by 1911Tuner rather than by increased pressure? If a 158grain bullet is driven to 850 fps from a 1 7/8 inch barrel, wouldn't both the recoil and the resultant battering of the gun be the same regardless of the chamber pressure contained by the cylinder which is doing the driving? Wouldn't the force striking the breech be the same regardless of pressure? Is pressure the enemy of older airweights or is it battering and recoil? If the latter, wouldn't heavy loads at higher velocities be detrimental regardless of the pressure generated in reaching those higher velocities? I just can't see the possibility of a "free lunch".

[1911Tuner]

Gary, it isn't so much the pressure that stretches the frame as it is the sudden punch at the beginning and the violent rise to peak. Friction between bullet and barrel also play a major role. Consider also, the bullet's construction. Lead or jacketed? Thick jacket or thin? Hard bullet core or soft? All these things are factors.

It's at least theoretically possible for a lower pressured round to create more stress on the frame than one with a +P rating. The old 200-grain .38 Special FMJ bullet at standard pressures is likely harder on frames than the 158 grain LSWCHP at +P pressures.

I have a 681 Smith revolver that I've shot long and hard with full-power .357 ammo loaded to near top-end pressures with a healthy dose of 2400 and a cast lead 160-grain bullet. Chronographed velocities are over 1300 fps. By best estimates, the gun has seen upward of 75,000 rounds of the stuff. Gauged headspace has increased less than .001 inch since it was new in 1991. That means that the frame has stretched less than .001 inch.
Several people who have handled it accuse me of babying it...and are amazed when I tell them how much it's been shot.

By comparison, an old friend of mine had a Model 13 that he bought about the same time, and it saw nothing but jacketed 158s with a half-grain less of the same powder...that loosened up to the point of needing service in less than 5,000 rounds. While L-frames are better able to handle the hard stuff than K-frames...there's not THAT much difference between the two.
He switched to cast bullets, and the gun has been singing along happily for lo these many years.

And...no. I don't get any leading in the barrel at those velocities, even with the relatively soft bullet aloy that I cast with. As in none.

So...There's more to that issue than can be predicted by pressure alone.

[Gary A]

1911Tuner - Thank you. You are aware of many more of the variables than I am but to the extent that I understand what's going on, I see what you are saying. Actually, in a limited way, that is part of what I was trying to get at in my posted question. Your comment that

It's at least theoretically possible for a lower pressured round to create more stress on the frame than one with a +P rating. The old 200-grain .38 Special FMJ bullet at standard pressures is likely harder on frames than the 158 grain LSWCHP at +P pressures.

is very telling to me. So much I don't know, but I have long been certain that just because a cartridge produces lower pressure doesn't mean it is less hard on the revolver given the other variables. Certainly this thread makes it clear that recoil for a given weight at a given velocity is going to be the same in a given firearm regardless of pressure variables. I can see why the Buffalo Bore loads are not jacketed, however .

[SCMtns]

My buddy and I read all the replies to this thread and kept thinking about things. He now says-- and I now agree-- that what we meant by "felt recoil" is actually acceleration, while the total foot pounds of recoil are kinetic energy. The two are entirely different quantities. We believe this is what Loosedhorse was getting at in one of the earlier replies.

My buddy emailed me yesterday that acceleration is the difference between two velocities divided by time, while kinetic energy is .5 times mass times the square of velocity. Nowhere in the formula for kinetic energy is time accounted for, and time is probably the critical factor in felt recoil. At least in this case, in which all other things are as equal as possible. I learned in boxing that "rolling with the punches" really does make a big difference in how hard a punch will land-- if it's too late to block, slip or duck, then if you can at least be moving slightly away from the punch as it lands you'll manage to take a lot off of it by simply extending the time over which the contact takes place. You'll still eat the full force of the blow-- you'll just do so more slowly.

So in our hypothetical example, a .44 and .45 will, in very slightly different lengths of time, push back on the hand with a virtually identical number of foot pounds. But a .44 will do so all at once, while the .45 will take very slightly longer to do so. Somehow it winds up making a big difference in the "feel" of the two weapons under recoil.

Thanks again to everybody who contributed.

PS-- Thanks to 1911tuner and Gary for the interesting info about pressure not being an all-important factor in wear and tear on a gun. I had no idea that would be the case.

[1911Tuner]

Yep. Many things not taken into account. Since the thread has evolved a bit, and headed toward points of internal ballistics, and how they relate to recoil and stress on the gun...

Note that some of this is proven, and some is theory, and while it's supported by pretty good evidence...it's not proven.

A powder's burn rate is relative, and it can change with different applications. Internal ballistics have long fascinated me...mainly because I've seen a few guns damaged and even blown up with recommended charges...because the loader didn't observe the cardinal rule:

"If you change ANYTHING...back off and work back up."

While I don't adhere to that religiously with changes in powder lots, if it's been several years between using data with a given powder, and buying a new lot of the same powder...I'm much more careful to work up to a (usually) new maximum. Alliant 2400 is a good example. It's a different powder than Hercules marketed in 1990 and the 2400 that Alliant is producing now. It's even different than it was when Alliant started making it. It's faster, and older data can land you in trouble. Take note

A given powder's relative burn rate changes with pressure. The higher the pressure, the faster it burns. A maximum dose of 2400 that's perfectly safe with a cast bullet can become dangerous if used with a jacketed bullet...and disastrously so if the jacket is thick and tough, and the lead core is hard.

Pressure spikes more quickly...earlier...when resistance goes up. A tougher bullet resists entering the rifling more than a lead bullet...and that charge of slow 2400 starts to burn more like relatively fast Unique.

A few things I've learned...sometimes the hard way...is that reducing case capacity by seating the bullet deeper spikes pressure more quickly than a little more powder. (This is why it's dangerous to use .357 data in .38 Special cases.) Increasing bullet mass drives pressures up faster than increasing powder charges....even if we adjust the seated depth to provide the same loading density. (The more massive an object is, the harder it resists aceleration.)

As far as the felt recoil being affected by the powder's burn rate...I haven't experienced anything to support that. The difference between Unique and 2400 simply isn't great enough for the human hand to be able to detect a difference if both are loaded to maximum pressures with a given bullet in a given gun. Load a .44 Magnum to equal pressures with a given bullet...one with Unique and the other with 2400, and you simply can't tell the difference, even though the velocities will be much different.

Muzzle velocity also isn't a reliable indicator of felt recoil. I've had detectably more severe recoil and lower chronographed velocities with fast powders than with slow powders and higher velocities. Since recoil is nothing more than the gun's momentum...and momentum is a function of Mass X Velocity...I have to suspect that the bullet's acceleration rate and hence its velocity is higher at some point with a fast powder...but because the fast powder starts to lose steam rapidly after the peak...less area under the curve...that the bullet actually loses velocity to friction as it travels through the barrel.

How does a bullet continue to accelerate to higher velocity after peak pressure and force starts to drop off? Newton 1B. "Objects in motion tend to remain in motion." It requires less force to keep an object moving than it takes to get it moving to start with, and it requires less force to continue to accelerate it to even higher speeds as it moves faster. So, either the slower powder maintains the bullet's velocity for a longer time/distance velocity after the peak ...or it simply doesn't lose as much to friction due to less barrel length remaining to bleed off the velocity. I suspect that it could be either one, depending on HOW slow the powder is, and how long the barrel is.

Consider too, that the harder an object is pushed...or the more quickly it's accelerated...the harder it resists. It requires a lot of force for a major-league pitcher to send a ball across home plate at 100 mph...but any 10 year-old can throw the same ball the same distance. The difference is in the rate of acceleration, and the force required to accelerate it.

Several years ago, a gun writer performed an experiment with a rifle and different powders...parting off an inch of barrel at a time, and recrowning. He found that...with some powders...he actually got quite a bit more velocity with less barrel length, so the theory of velocity loss due to friction seems to have merit.

[Gary A]

Wow! Fascinating stuff. Certainly a lot more to it than stuffing powder in a case and touching it off!!

[1911Tuner]

Certainly a lot more to it than stuffing powder in a case and touching it off!!

Yeppers. A wise man once wrote...can't remember exactly who:

"The pressure required to drive a 150-grain bullet to 3,000 fps in 22 inches of barrel is more than sufficient to blow your eyes through the back of your head."

Words to live by.

[mavracer]

Yes, two guns both flinging, say, 300gr downrange at 1,300fps will have the same recoil assuming the guns weigh about the same.

However, if one is getting there with 24,000psi while the other is hitting 34,000psi, the difference is that the lower-pressure setup is spreading the force applied to the bullet over a broader range of time. We're talking about very small periods of time(!) but it still makes a difference in how you feel that recoil. The high-pressure load will feel more like a "slap", the low-pressure load more like a big fat "push".

the thing your forgetting is the reason the 45 can do at 24,000 psi is there's more SI.rember pounds per square inch.
the amount of powder used has a minute affect on recoil but pressure does not assuming gun weight, bullet weight and velocity are all the same.
unless we're talkin ported or compensated guns then the higher pressure will affect felt recoil.

[1911Tuner]

As a final note...

If there's any doubt as to how much recoil can be generated by low pressure...

Occasionally, you can find some old, unused balloon head .45 Colt cases at gunshows. If you can find any that are useable...assemble a few rounds using the original loading of 40 grains of 3f black powder under a 250-grain lead bullet...and fire it in a Colt 1873 SAA or a modern revolver of similar bulk..like a New Vaquero.

I've done it, and it's a handful.

Or...go shoot a Sharps 45-110 with a full charge of black powder and a 500-grain bullet. There's no long, drawn-out push. It'll bring tears to your eyes. Try an 8-pound Sharps Cavalry Carbine .45-70 with 65 grains of 2f and a 405-grain bullet. Guaranteed to satisfy the most hardcore recoil freak. I've got one. I've shot it with that load. 10 rounds a month is plenty.

Or, even consider the lowly 12-gauge shotgun, and the normal operating pressures with a standard, 9 pellet 00 Buckshot load. Low pressure again...but not very gentle.

[zxcvbob]

I think (when loaded to the same ballistics) the recoil will be about the same, but the .44 will be LOUDER.

[1911Tuner]

I think (when loaded to the same ballistics) the recoil will be about the same, but the .44 will be LOUDER.

Depends mostly on the powder. Slow burners like Olin 296 and H-110 produce a horrible muzzle blast and concussion that'll give ya a headache. Equal pressures with a faster powder...not so much.

[Loosedhorse]

Or...go shoot a Sharps 45-110 with a full charge of black powder and a 500-grain bullet. There's no long, drawn-out push. It'll bring tears to your eyes.

This again points to the importance of impulse for perceived recoil.

Smokeless powder is not considered an explosive. Black powder is a low explosive (its burn rate is about 1000m/sec, and it will explode when ignited, even if unconfined), so the whole charge "goes up" at once--and gives quite a jolt.

The reason that smokeless powders are famous for generating excess pressure is that they contain more energy per volume (3-4 times more) than does black powder: so you can "over-fill" black-powder-era cases to unsafe pressure if you use a full-volume fill of smokeless.

I would expect that if you filled the 45-110 with black powder, and then filled another cartridge with ONLY ENOUGH smokeless powder (plus whatever filler you might want to prevent mythical "detonations") to generate the same muzzle velocity (that is, same total recoil), you'd feel the smokeless-filled cartidge as giving a more bearable recoil, cetera paribus--because of the slower burn rate, slower pressure rise, and lower initial impulse.

[Vern Humphrey]

(plus whatever filler you might want to prevent mythical "detonations")

I'll point out the mythical detonation effect has been duplicated under laboratory conditions at least once.

It is not a detonation. What happened is the powder charge was too small to fill the case up to the flash hole when the case was held horizontally for firing. The primer flashed over the powder charge, drove the bullet into the lede, and a split second later, the powder charge ignited. The bullet, stuck in the lede, acted as a bore obstruction.

This occurred, as I recall, while testing loads for the 6.5X55 Mauser.

[Loosedhorse]

That could make sense--bullet lodges in lede due to primer force alone, while the rest of the cartridge experiences a hang-fire, and finally ignites with a now-blocked barrel.

As long the primer alone can propel the bullet, and this powder set-up can cause a hang-fire, we're all set.

[Vern Humphrey]

It happened at least once, in a laboratory, with pressure measuring equipment that clearly shows the blip of the primer, then a steep spike as the main charge goes off and impacts the stuck bullet.