9mm 115gr vs 124 gr vs 147 gr

absolutely, especially shooting 147's. Much 'slower' and easier to deal with vs. 115's

It depends on how fast each bullet is loaded. Really slow 115 gr bullets are going feel better than +P 147 gr but if all three bullets (115, 124, 147) are loaded to the same Power Factor* (ie total recoil impulse) then most shooters will find that the heavier bullet will feel softer shooting. In reality if they are all loaded to the same power factor they all have the same total recoil impulse but because the heavier slower bullet take longer to accelerate to its final velocity it feel softer, more push and less snap.

*Power Factor is a common unit for recoil used by competitive shooting sports like USPSA, IDPA, 3GN etc. It is simply bullet mass in grains times velocity in feet per second divided by 1000 to scale the resulting number to convent size. It is for all intensive purposes the momentum change (total recoil impulse) of the bullet with funky units (slug-ft/sec or kg-m/sec freaks everyone out). The total recoil impulse felt by the shooter also includes the mass and velocity of propellant gases but in a handgun that is a relatively small proportion of the total recoil and almost negligible for most shooters.

mcb said:

In reality if they are all loaded to the same power factor they all have the same total recoil impulse but because the heavier slower bullet take longer to accelerate to its final velocity it feel softer, more push and less snap.

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Not quite true. The lighter bullets will require a greater charge of powder to achieve the same power factor as the heavier bullets. This powder has an influence on recoil, too, beyond just its contribution to the momentum of the bullet. The gasses generated by the burning powder have mass. They also have velocity - a lot of velocity! More than the bullet itself. So they punch above their weight (almost literally) in terms of their contribution to recoil. Thus, when you include the jet of gas coming out of the muzzle, the lighter bullet using a larger charge of the same powder than the heavier bullet will have more total, actual recoil... separate and apart from the subjective perception of more "recoil" coming from the blast and flash.

Here's an interesting article that tested this concept mechanically. http://www.shootingtimes.com/reloading/power-factor-recoil-bullet-weight-gives-edge/

Also, note that all of the above gets turned on its head when a compensator or ports (any device that uses the gasses to mitigate recoil) comes into the picture.

ETA: There are also some problems with the duration/rate of acceleration explanation for why shooters would experience a difference in recoil between two identical power factor loads. Especially in a semi-automatic gun, where the bullet is gone from the barrel before the vast majority of recoil forces are imparted to the shooter (which doesn't happen until the slide hits the rearmost end of its travel).

TheDomFather said:

Thanks for the info, I shoot a little in action pistol and IDPA and was wondering if switching to heavier projectiles would help me stay on target. Im shooting Ranier 115gr plated HP today with 4.4 gr of Bullseye behind it. It mostly what I have shot since I started reloading but I now have a bunch of other powders I am going to test as well. For .45 ACP I have been shooting 185gr Hornday XTP but now I have 200gr Ranier plated HP and also some 230 gr to test as well.

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No Problem. I think you will find the most action pistol guys are shooting bullets heavy for caliber in most divisions. 147gr in 9mm, 180gr in 40S&W (some even load 200gr but usually loaded long for the 2011s) and 230gr in 45 ACP. The only real exception is USPSA Open division as its hard to load a 147gr bullets to Major power factor in 9mm or 38 Super/Super-Comp and not have pressure issues and/or enough propellant gases to make the compensator work well. . Most Open shooters find 124gr work better as there is more case volume for propellant to get the bullet up to Major Power factor and have enough propellant mass to make the compensators work well without pressure issues.

Yeppers, all things being equal bullet weight does make a difference.

I've settled on a 124 grain jacketed/plated RMR Round Nose as my competition bullet for both my pistol and my Pistol Caliber Carbine with either 4.0 grains of TiteGroup or 4.3 grains of 231/HP38.

I'd actually prefer to go with 147 grain, but with all the blasting my wife, grandson and I do, 124 is more budget friendly and a good compromise.

ATLDave said:

Not quite true. The lighter bullets will require a greater charge of powder to achieve the same power factor as the heavier bullets. This powder has an influence on recoil, too, beyond just its contribution to the momentum of the bullet. The gasses generated by the burning powder have mass. They also have velocity - a lot of velocity! More than the bullet itself. So they punch above their weight (almost literally) in terms of their contribution to recoil. Thus, when you include the jet of gas coming out of the muzzle, the lighter bullet using a larger charge of the same powder than the heavier bullet will have more total, actual recoil... separate and apart from the subjective perception of more "recoil" coming from the blast and flash.

Here's an interesting article that tested this concept mechanically. http://www.shootingtimes.com/reloading/power-factor-recoil-bullet-weight-gives-edge/

Also, note that all of the above gets turned on its head when a compensator or ports (any device that uses the gasses to mitigate recoil) comes into the picture.

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Sure but I was not sure how deep into these weeds we wanted to go. Powder in pistol "punches" about 1.5 time its weight in the recoil department. So in say a 180gr 40S&W load with 5gr of propellant the propellant still only accounts for less than 5% of total recoil. Even in the article you post the difference between a 185gr and 230gr loaded to the same Power Factor differed by less than 10% when the propellant mass was factored in. Not say it does not matter just that it plays secondary to the impulse time lengthening you get from 185 to 230, but it all plays a part.

I address the Open issue a little in my second post in the thread. The Compensator does change the strategies.

For 9mm, my Hornady manual indicates better results using progressively slower powders as bullet weight increases.

I think that matters. 10% is a lot in competitive shooting. I also think that it's problematic to say that real differences are all subjective. When people hear that something is "subjective," a lot of them will decide that it means that there is no wrong answer and/or that it's not worth bothering with. I think it's better to answer the question:

• Yes, there is a real difference in recoil by projectile weight for a given power factor.
• In pistols at least (IDK about rifles - bottleneck rounds may be different in some way), and in the absence of comps or porting, the heavier bullet will make PF with less actual recoil.
• In addition, many shooters find that the reduced blast/flash of the reduced powder charges needed by heavier bullets further increases the sensation of reduced recoil.
• Different people end up preferring different things (maybe their gun runs better on lighter bullets, or the cost difference matters to them, or whatever), but it is definitely worth experimenting with heavier bullets (at the same PF) to see if you enjoy them and/or see a benefit in your shooting.

Zendude said:

For 9mm, my Hornady manual indicates better results using progressively slower powders as bullet weight increases.

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What do you mean by "better results"?

ATLDave said:

What do you mean by "better results"?

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To be honest, I'm not exactly sure. The manual has 7 or 8 recommended powders for each bullet. I can see that the recommended powders get slower as the bullets get heavier. I think faster powders have a harder time getting higher velocities with heavier bullets while staying under the max pressure.

Zendude said:

I think faster powders have a harder time getting higher velocities with heavier bullets while staying under the max pressure.

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That is surely true. If you are chasing a higher velocity, then that will generally steer you towards the slowest powders that will work in a given cartridge; and heavier bullets will help generate enough initial pressure and dwell time for slightly slower powders than lighter bullets in the same cartridge.

If, however, you are chasing a particular power factor* and/or the lightest recoil that will operate your gun, then faster powders are generally going to be the answer. Even under heavier bullets.

"Better" depends entirely on your goal!

*Assuming the PF is well within the window of the cartridge in question - e.g., it's not hard to get to 130 PF with 9mm, so you don't need to go looking for the most possible velocity.

This article has been quoted a few times http://www.shootingtimes.com/reloading/power-factor-recoil-bullet-weight-gives-edge/ and will probably give you some answers.

My apologies ATLDave. Just realized you already quoted the article in this thread:

ATLDave said:

Not quite true. The lighter bullets will require a greater charge of powder to achieve the same power factor as the heavier bullets. This powder has an influence on recoil, too, beyond just its contribution to the momentum of the bullet. The gasses generated by the burning powder have mass. They also have velocity - a lot of velocity! More than the bullet itself. So they punch above their weight (almost literally) in terms of their contribution to recoil. Thus, when you include the jet of gas coming out of the muzzle, the lighter bullet using a larger charge of the same powder than the heavier bullet will have more total, actual recoil... separate and apart from the subjective perception of more "recoil" coming from the blast and flash.

Here's an interesting article that tested this concept mechanically. http://www.shootingtimes.com/reloading/power-factor-recoil-bullet-weight-gives-edge/

Also, note that all of the above gets turned on its head when a compensator or ports (any device that uses the gasses to mitigate recoil) comes into the picture.

ETA: There are also some problems with the duration/rate of acceleration explanation for why shooters would experience a difference in recoil between two identical power factor loads. Especially in a semi-automatic gun, where the bullet is gone from the barrel before the vast majority of recoil forces are imparted to the shooter (which doesn't happen until the slide hits the rearmost end of its travel).

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That article is so interesting, it's worth double-posting it!

Muzzle energy is the velocity squared, whereas the "power factor" formula used for competition does not square the velocity. So, the power factor formula favors heavier bullets. In other words, for heavy and light bullets both meeting the minimum power factor, the heavy bullet will have less muzzle energy and therefore less felt recoil.

https://www.thehighroad.org/index.php?threads/muzzle-energy-vs-power-factor.533019/

As most 9mm handguns are short recoil action (as opposed to blowback) it should be possible to load 115gn bullets to recoil the same as 147 and still operate the action, although the lighter bullet will be in the barrel for a shorter time and may change the felt impulse. For me, I like the 115 bullets for 9mm and have loaded them for reduced recoil for my wife's gun, and the price is right.

Toprudder said:

In other words, for heavy and light bullets both meeting the minimum power factor, the heavy bullet will have less muzzle energy and therefore less felt recoil.

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Everything up to that was right. I'm not sure that part is. I don't think muzzle energy is directly related to recoil.

ATLDave said:

Everything up to that was right. I'm not sure that part is. I don't think muzzle energy is directly related to recoil.

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Ok, then this:

https://en.wikipedia.org/wiki/Free_recoil#Calculating_free_recoil

Felt (on edit: should be FREE) recoil is still a squared function of velocity.

And this.

http://saami.org/PubResources/GunRecoilFormulae.pdf

TheDomFather said:

for you guys is as a shooter do you notice any difference in feel and recoil impulse in shooting heavier bullets?

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124s seem a little bit stouter to me than 115's, but not enough to really impact my shooting. However, the POI changes a bit.

Toprudder said:

And this.

http://saami.org/PubResources/GunRecoilFormulae.pdf

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It has been a long time since I took any math classes, but I don't think you're reading that right. (You're not squaring velocity alone, as when doing KE calculations).

Momentum is the way to calculate equal-and-opposite reactions. At least that's how I recall my high school physics class.

For instance, few people dispute that a 7.62x39 recoils more than a 5.56, yet the 5.56 typically has as much or more KE.

Toprudder said:

Ok, then this:

https://en.wikipedia.org/wiki/Free_recoil#Calculating_free_recoil

Felt recoil is still a squared function of velocity.

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Free recoil has a square term but it the velocity of the firearm and has little to do with the energy of the projectile.

What is felt recoil? It's too subjective to put a number on "felt recoil". Recoil is a really nasty nut to talk about. There are many ways to put a number on it depending on the context we want to examine. The three most common are recoil impulse, free recoil energy and peak recoil force.

Recoil Impulse is the simplest. It is simply the change in momentum. Mass x Velocity of everything spit out the end of the barrel. It unfortunately leaves a lot of details out of it as it lumps all of it together. It also does not take into account what it is being fired from. (ie 357 mag from a 12 oz J-frame hurts, the same cartridge from a 40 oz N-frame, not too bad).

Free recoil energy is a theoretic metric, that does take into account the weight of the firearm. Free Recoil Energy is what Kinetic Energy would the firearm have if left to go the opposite direction from the bullet when fired if attached to nothing (ie zero-G). It is calculated off the above Recoil Impulse. A law of physics is that momentum is always conserved. If ,in our theoretic unsupported firearm setting, the bullet and propellant go one way with X amount of momentum the rifle must go the other way with the same amount of momentum. So the following has to be true in that setting. Mb x Vb + Mp x Vp = Mf x Vf. [ M = mass, V = velocity, b = bullet, p = propellant gases, f = firearm] Momentum does not sit well in most peoples heads so its common to take the resulting velocity of the firearm from the conservation of momentum equation and calculate the resulting kinetic energy the firearm would have. Free recoil energy is then 1/2 Mf x Vf^2. Notice that if you calculate the kinetic energy of the bullet and propellant it will NOT be the same as the firearm (good thing too). But in reality a firearm rarely achieve its free recoil energy since you are holding (hopefully firmly) onto the firearm and your body mass and muscle tension/elasticity effect the recoil greatly. But it is a good number to compare that takes into account the cartridge and the weight of the firearm firing it.

Another metric some measure is peak recoil force and impulse time. This take some good measurement equipment that can measure forces very fast. It is very subjective because the force of recoil will change a lot depending on how the firearm is supported in the recoil force measurement system. It is really only valid for measurements used comparatively when taken in the same test setup the same way. Recoil pad manufactures love this number as a soft recoil pad does nothing for to recoil impulse or free recoil energy but it does reduce the peak force and spread the recoil out over time making it feel softer. This method is also the only one that will capture the felt recoil reduction most shooter experience when shooting a semi-auto compared to a similar weight and caliber weapon of a manual action. If this measurement is done correctly then if you integrate the force vs time curve you should arrive at the same number as the Recoil Impulse calculation.

^ This guy engineers! LOL! Great post.

mcb said:

This method is also the only one that will capture the felt recoil reduction most shooter experience when shooting a semi-auto compared to a similar weight and caliber weapon of a manual action. If this measurement is done correctly then if you integrate the force vs time curve you should arrive at the same number as the Recoil Impulse calculation.

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Purely academic question (from a layperson): wouldn't you lose at least a little heat loss of energy... like in the springs and the frictional heating of the bolt/slide/whatever? Probably utterly trivial in terms of any perception...