9mm 115gr vs 124 gr vs 147 gr

[Bama59]

I just recently been shooting 147 gr since it has been on sale. It performs well in M&P Shield but hits low with SD9 and 5906. The light weight SD9 is very snappy and Shield has recoil but feels more solid plus been shooting it three years. Little recoil shooting 115 and 124 gr with hefty 5906,can go through 200+ rounds no problem.

 

[George P]

IF you loads all three to the same velocity, then the 147 will have the greater amount actual recoil - that is Newton.

 

[mcb]

^ This guy engineers! LOL! Great post.



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...

Yes you loose quite a bit of energy but the force vs time curve is a time dependent measure of the momentum change not the kinetic energy change, though they are interconnected.

 

[Toprudder]

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 it firing.

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 rid 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.

Great post!

Yes, I typed "felt" but meant "free" as was mentioned in the article.

Felt, as you mentioned, is highly subjective.

As for the weight of the gun affecting the perceived recoil, for the sake of this discussion, the gun is not a variable as it would be assumed to be the same and the only difference will be the loaded round. The variables would then be the weight of the projectile, muzzle velocity, and ejected gasses. My main point is that the general consensus of the competition crowd is that a heavier bullet will be less recoil for a given power factor. This does not mean that a light bullet cannot be loaded to the same recoil, just that it will not meet the required power factor.

 

[sbwaters]

My letter carrier prefers 124 to 147 gr.

 

[Toprudder]

My letter carrier prefers 124 to 147 gr.

LOL. My UPS guy absolutely HATES 230gn 45acp, especially the ones in the 2000pc bulk buckets.

 

[mcb]

Great post!

Yes, I typed "felt" but meant "free" as was mentioned in the article.

Felt, as you mentioned, is highly subjective.

As for the weight of the gun affecting the perceived recoil, for the sake of this discussion, the gun is not a variable as it would be assumed to be the same and the only difference will be the loaded round. The variables would then be the weight of the projectile, muzzle velocity, and ejected gasses. My main point is that the general consensus of the competition crowd is that a heavier bullet will be less recoil for a given power factor. This does not mean that a light bullet cannot be loaded to the same recoil, just that it will not meet the required power factor.

Exactly.

And to take this to maximum advantage many competitive shooter will pick the heaviest bullet coupled with the fastest powder than can use to get to the required velocity and not have a pressure issue since this will reduce the mass of the propellant as much as possible.

ALTDave in your ETA in an earlier post where you talk about duration/rate of acceleration, after thinking about it some more I think you may be right that in a semi-auto action assuming everything is loaded to the same power factor (bullet only) that the reduced recoil due to the smaller amount of propellant probably is a more important factor than then the increase bore time of the slower heavier load.

It would be interesting to see if we loaded two cartridges one with a light for caliber bullet and the other with a heavy for caliber bullet to the same total recoil impulse (taking recoil from propellant into account this time) if a shooter could feel the difference. If you are right ALTDave they probably couldn't in a semi-auto. The interesting part would be if they could in a manual action like a revolver. Can your body sense an increase in bore time that probably measures on the order of 0.1-0.3 milliseconds and would it actually feel different/better? I think not many would be able to.

 

[sbwaters]

I don’t like where this is headed.

Two barrels fastened horizontally on a center pivoting axis with a single firing mechanism to fire them at the same instant with the barrels deflecting to one side or the other based on recoil and the resultant deflection of the two bullets on the target telling the tale.

But which bullet is which?

 

[ATLDave]

You don't need to do them simultaneously. See the previously cited Shootingtimes article that used a ransom rest to measure empirical differences in recoil.

 

[ATLDave]

Can your body sense an increase in bore time that probably measures on the order of 0.1-0.3 milliseconds and would it actually feel different/better? I think not many would be able to.

I used to think one could, but now I do not. I think it would be like trying to time something that happens in either 5 seconds or 7 seconds by using a watch with only a minute hand. I strongly suspect that all the different subjective feelings of recoil are about the stuff we discussed earlier and about the differences in what comes out of the muzzle (or B/C gap) in terms of blast and flash. Maybe that would be effected by the bore time (in terms of what pressure is behind the bullet when it "uncorks" at the muzzle), but bore time itself? I think that's sub-resolution of people's internal perceptional clocks.

Or maybe my brain's clock speed just isn't fast enough. Maybe that's why I'm not a GM!

 

[wrench459]

Lets see if I can ask this correctly.
With three bullets 115,124 and 147 with the same amount of powder.
Same amount of bullet mass into the shell.
Which one has more felt recoil?

 

[TheDomFather]

With those 3 bullets max load will decrease in grains with the same powder as bullet weight goes up. If you loaded the same powder and same weight across 115, 124 and 147 your 115 load would either be really light or your 147 load would be way over max and very compressed assuming same OAL.
Dom

 

[wrench459]

I don't think that I included COAL into the mix.
Just same powder load,bullet mass into the shell and recoil effects

 

[TheDomFather]

I don't think that I included COAL into the mix.
Just same powder load,bullet mass into the shell and recoil effects

I am going to shoot some 185 and 200 gr .45 side by side, I will load the both with the same powder at max .1 - .2 gr below max published charge for the given projectile and to the published recommended OAL. I will shoot them side by side to see if there is any noted different in recoil charecteristics. I also have some .230 gr so I can add that to the mix as well. I can also do this for a few different powders.

Let’s put the lighter is snappier to the test and see what we can come up with.

I will shoot them all out of a Sig P227 Tacops. Might be a good video series.

Dom

 

[ATLDave]

Let’s put the lighter is snappier to the test and see what we can come up with.

If you're loading them all to max, I'm not sure you're testing the actual claim that some people are making. The claim is that when loaded to the same power factor/momentum the lighter bullet will have more recoil. Max is generally set during load research by peak pressure, or by a level at which the peak pressure becomes unpredictable/non-linear/oversensitive to tiny changes in inputs.

If a max load of 230 gets you to a significantly higher total momentum/PF, there's little suspense about whether it will have more recoil than a 185 that (while also at max) has a significantly lower momentum/PF. "Proving" that with a video wouldn't really be new information. As for whether max loads have higher recoil with heavier or lighter bullets, a quick look at the reloading books and calculating PF's will get you a pretty good sense of the answer.

Short version: Make sure you don't debunk a claim that isn't being made!

 

[ATLDave]

Lets see if I can ask this correctly.
With three bullets 115,124 and 147 with the same amount of powder.
Same amount of bullet mass into the shell.
Which one has more felt recoil?

As Dom pointed out, that's not really the way anyone loads. Different weight bullets generally get different powder charges, since adding bullet weight raises peak pressures.

But if we look for different bullet weights and powder combinations that have some overlap within a safe range, we can see that the heavier bullet load is going to have significantly more momentum, and, therefore, more recoil. That's because the heavier bullet has longer time in the barrel during which the combustion of the powder can impart additional energy to it, which results in additional momentum. Now, it's still going slower than the light bullet, but not slower enough to offset the greater mass.

That's another way of understanding why, for the same momentum/power factor, the heavier bullet will have less recoil - it will take less powder. That's the same thing we were discussing above, just coming at it from the other end.

 

[fxvr5]

Lets see if I can ask this correctly.
With three bullets 115,124 and 147 with the same amount of powder.
Same amount of bullet mass into the shell.
Which one has more felt recoil?

Are you saying that each bullet is loaded to the same depth in the case? Not sure why you're specifying this. It's not something we normally do in the real-world. In fact you would end up with crazy overall lengths if dealing with 115 and 147 grain bullets.

The simple question of which would have more recoil if they are all loaded with the same powder charge (and at the same overall length) is obvious. The heavy bullet would. Table 2 in the article cited shows actual velocities in that condition.

With respect to answering one of the other questions asked, such as what if each weight is loaded to its max speed, one can simply look at a loading manual, and using the same powder, determine the recoil force that each would get based on speed and charge weight for that data using a recoil calculator such as the one here: http://kwk.us/recoil.html

The Ransom Rest results are very consistent with the math model, so the math will give you the answer.

 

[Dudedog]

I prefer 124s but a lot of it is preference.
As noted above a 147 loaded to the same PF will have less muzzle energy than a 124 at the same PF which will have less than a 115 at the same PF.
My guns shoot 124s better than 115s, 147s seem to shoot better than 115s for me as well. (longer bearing surface maybe)
I prefer 124/125s.

 

[Toprudder]

Lets see if I can ask this correctly.
With three bullets 115,124 and 147 with the same amount of powder.
Same amount of bullet mass into the shell.
Which one has more felt recoil?

I don't really think your scenario applies to the OP, but it is an interesting question. I have data from my reloading that suggests the heavier bullet will be faster, given the same charge. But those were loaded to the same OAL, not the same depth into the case. This is something that I would like to try, though. I have a 45acp revolver that I can load to longer OAL than will plunk in my semi-autos.