9mm versus 40

[JMichaelTX]

I realize this is an emotional debate for many people, but as a recent buyer of a M&P Shield, I have been looking for more objective rationale for selecting one caliber over the other. While I initially selected the Shield 40, I have come to question that after considerable research. So, if the data conclusively points to the 9mm being materially better at knockdown or stopping power, then I will consider switching to a Shield 9mm.

I have read much, watched many YouTube videos, and, except for the cost of rounds, it seems to me that it is much like a tie, a personal preference.

The last few days I have been researching defensive rounds, i.e., Jacketed Hollow Points (JHP), trying to determine what are the best choices. For me, cost is not a consideration here, since I will be firing very, very few, if any, JHP rounds after some initial testing. I am a private individual, with no need to fire unless threatened.

So, I came across this very interesting table on the Winchester web site, for the PDX-1 ammo, which seems to be one of the best, highly rated by many.

As you can see, the 40 cal 165 gr has 20% greater energy than the 9mm +P 124 gr.

Seems to me, with all other things being equal, that greater energy means greater knockdown power.

I don't expect to change the mind of anyone who has already made this decision, but I thought it might be of some help to others, like me, who have not made a decision yet. I would not make a decision based on this one table alone. It is just another data point to be considered.

For anyone else researching this question, I would encourage you to do a lot of your own research, both in this forum and elsewhere. While there are a lot of biased authors/presenters out there, there are also a number of reasonably objective articles, blogs, and videos available.

 

[Mark40]

People put too much emphasis on power in defensive handgun caliber choices. That 20% difference in muzzle energy is not that significant. All semi auto calibers are wimps compared to rifle ammo. With modern ammo, 9mm, .40 .45 are all adequate. But shot placement is everything. In a small gun like the Shield, I'd stick with 9mm. But that's just my humble opinion. I've always liked .40, and I carry a 40c every day. But if I'm honest, it is a bit of a handful with some ammo.

 

[Mark40]

Knockdown power is also a myth with handgun ammo. The only way to get a one shot stop, is with a central nervous system hit.

 

[John R]

Nine is fine, I just like the 40 better.
It's a choice we all have to make for ourselves.

 

[Houlton]

9mm or 40

INMHP the best one of the two is the one you can put every round in a 6" circle at short gun ranges. If you can hit your target with a 9mm and not a 40 the 9 is your best bet. As a Police Officer I saw a lot of folks dead form a variety of weapons. I'm not sure about the term instantly killed but I saw one I think would qualify. A woman shot her boyfriend with a 22 rifle from about 25 feet. He was lighting a cigarette. Was on the floor with cigarette in one hand and matches in the other. Had a smile on his face. Never knew what hit him. I don't recommend a 22 for defense, but if its what you can hit your target with use it. A 22 in the chest or head will kill when the loud noise from a 44 mag ain't gonna do you no good.

 

[McE]

List all the differences, then rank them in order of importance to you.

On that list, I would have capacity and follow up shot time ranked as more important than the muzzle energy figures. Like you, I would put cost pretty far down on the list because in the grand scheme of things, I wouldn't be shooting that many of them.

In fact, Federal's own testing of their HSTs have shown the 9mm to perform slightly better than their 45 of the same bullet, even though the 45 has a significantly higher muzzle energy number.

 

[41 fan]

There has been much written and discussed about the effectiveness of different calibers and loads. To my knowledge there is not or never been anything engraved in stone. There are just too many variables involved. I believe accuracy is the most important thing. Dean

 

[federali]

Pitting the 9mm against the .40 S&W is bound to get peoples' attention. Muzzle energy is but part of the total equation. You might want to research the FBI's recent decision to return to the 9mm from the .40

 

[gen3guy]

If I could only have one, I'd go with the 9. It's cheaper. It's lighter. It's effective. And it's everywhere.

 

[Saudade]

Gee. More proof that blah-blah is better than yada-yada.

If you like .40, then shoot .40. Yes, it's that simple.

"All other things being equal" never happens in the real world, let alone in a self defense scenario.

 

[AlHunt]

6 of one, half a dozen of the other. The only factor I'd consider is reloading and it sounds like that's not an issue for you.

 

[McE]

I said this in the other thread.

Everyone, and I mean literally everyone, shoots better with the 9mm than the 40 of the same gun. It's that simple.

You can enjoy shooting whatever you want, you can carry whatever you want, you can enjoy/like/prefer anything, but be honest about your priorities. For some people, being able to say "I shoot the 40 cal" while believing the 9mm is ineffective is more important to them than what they would shoot better. If optimizing your performance in life or death situations is not a priority, that's completely your prerogative. Saying you like/prefer the 40 is a mutually exclusive statement to saying you like/prefer shooting your best. My problem with it comes in when such people try to convince others they need the 40.

 

[JMichaelTX]

You might want to research the FBI's recent decision to return to the 9mm from the .40

Thanks for the suggestion. I had previously read several articles on this, but to be sure, I searched again, and found this excellent blog:

FBI 9mm Justification, FBI Training Division

Not only is the blog interesting, the the follow-on comments by readers is fascinating. If anyone has not read this particular blog, it is definitely worth a read.

This link was provided by one of readers, looks to be very interesting:
Best Choices for Self Defense Ammo

 

[kcbet2]

Two words. Shot placement. Energy, caliber, knock down mean nothing if the shot isn't in the right place

 

[Ballistic147]

For years now I've owned a .22, .380, and a 40 pistol. I purchased a Ruger P91DC back when the 40 had first come out. Up until I purchased a Shield 9mm back in January I had never owned anything in 9mm. Why did I choose the Shield in 9mm? Strictly for that one extra round. Just last weekend I purchased an M&P 40c. Been looking at the compacts since I bought the Shield. So why choose the 40c over the 9c? I really couldn't tell you.

I've been shooting for a little over 20 years now and in no way consider myself an expert. As far as I'm concerned there's really no considerable difference between the 9 and 40 as far as stopping power goes and I don't feel that one is particularly better than the other. I shoot both well and am equally happy with both. It may seem strange to some but I feel no more manly when shooting the 40 than I do when shooting the 9.

Both are great calibers and it's up to each individual to decide for themselves which is the most appropriate for their situation. I actually like both and have chosen to own both.

 

[s&w-noob]

i would choose 9 because:
-higher capacity
-less recoil
-quicker follow up shot
-less wear on the gun
-cheaper ammo
-knockdown power is about the same

just read the newest FBI ballistic tests, they are switching back to the 9s from the 40s because they have basically the same power, are easier to shoot and you get more ammo

 

[trooper2899]

If U touch off a 40 in an enclosed area or inside a vehicle it will negatively effect your hearing (more so than a 9mm) If you're in a low light situation and there's still a threat your hearing could be vital, If U have a situation where U fire multiple rounds in rapid succession at center mass your recovery between rounds won't be as good with a 40 (in a 3.5 in Barrel) because its harder to group shots especially in a stressful situation.
I say 9 is fine for self defense up close and personal.

 

[JMichaelTX]

FBI 9mm Justification, FBI Training Division

This is the most detailed article I have found that actually quotes the FBI report that recommends changing to a 9mm standard for LEO.

While it is detailed in some respects, it does not actually provide the technical results of the many tests they (the FBI) claimed to have made. I would be much more comfortable in accepting their summary results if they also published the actual data.

I think we have to start with this:

1. The FBI is a government organization.
2. Most, if not all, government organizations tend to make statements/reports that justifiy their actions/decisions, regardless of the facts.
3. Do you really trust the government?

Then, we must consider this statement in the FBI report:

In short, extensive studies have been done over the years to "prove" a certain cartridge is better than another by using grossly flawed methodology and or bias as a precursor to manipulating statistics.

Presumably, these studies were either made by, or authorized by, the FBI. So, if they lied/misled in the past, why should we trust the current report?

So I have to say that I don't trust any report from any government agency, including the FBI, unless they provide supporting, detailed, data.

Perhaps more important than the caliber of the handgun used, are the following statements the FBI made:

1. In all the major law enforcement calibers there exist projectiles which have a high likelihood of failing LEO's in a shooting incident and there are projectiles which have a high ting incident likelihood of succeeding for LEO's in a shooting incident

4. LEO's miss between 70 – 80 percent of the shots fired during a shooting incident
. . .
Shot placement is paramount and law enforcement officers on average strike an adversary with only 20 – 30 percent of the shots fired during a shooting incident.

9. There is little to no noticeable difference in the wound tracks between premium line law Auto enforcement projectiles from 9mm Luger through the .45 Auto

I have added numbers to the FBI Summary Report in order to clearly identify the paragraph in the FBI report.

In paragraph #1, it seems clear that the FBI needs to identify which ammo likely leads to failure, and which ammo likely leads to success. Whether it be 9mm or 40cal, we need to know this!!

#4: Clearly the FBI and LEO's need much better training so that they can improve on their 30% hit success.

#9: In spite of the FBI recommendation, there is no evidence that 9mm provides any improvement over larger rounds (.40, .45).

Seems like the FBI has a lot of work to do to improve their own firefight efficiency/success, as well as LEOs in general.

 

[wingriderz]

i would choose 9 because:
-higher capacity
-less recoil
-quicker follow up shot
-less wear on the gun
-cheaper ammo
-knockdown power is about the same

just read the newest FBI ballistic tests, they are switching back to the 9s from the 40s because they have basically the same power, are easier to shoot and you get more ammo

Ok I own bolth more than one 9mm in other brands all have been flawless. I agree on higher. Capacity. Not sure on quicker follow up shot.and less wear? Wal mart selling 40 for a buck less than 9mm at the moment. I just bought. The. M&P40C last month. Haven't. Had time to run it yet , but will soon

 

[V0OBWxZS16]

Please don't use the terms "knockdown power" and "stopping power". They make puppies cry.

Kinetic energy is not a valid measure of projectile performance and is a very common error. What's Wrong With The Wound Ballistics Literature, And Why (Subsection 4: Presumption of "Kinetic Energy Deposit" to Be a Mechanism of Wounding) by Dr. Fackler. What is valid is determining the depth and size of the wound made in flesh (or valid flesh simulant.) Dr. Roberts obtained the following results for two HST loads. Both loads give penetration depths in the desired range and the .40 had a 0.05" greater recovered diameter than the 9. My understanding is that pistol bullets create wounds smaller than the recovered diameter of the projectile so the actual difference is even less.
9 mm Fed 147 gr HST at 1005 fps:
BG: Pen = 14.0, RD = 0.65, RL = 0.41, RW = 147.6
4LD: Pen = 16.5, RD = 0.60, RL = 0.53, RW = 147.5

.40 Fed 180 gr HST (P40HST1) at 986 fps:
BG: Pen = 13.8, RD = 0.70, RL = 0.33, RW = 181.5
4LD: Pen = 15.8, RD = 0.65, RL = 0.48, RW = 183.5

"All else being equal" the .40 is very slightly better than the 9mm. However all is NOT equal. Projectile performance potential is useless without being placed in the correct location and needs to be balanced with many factors to achieve maximum system efficiency. Some of the other factors are speed, accuracy, capacity, and training ammo cost. If you assume that it takes more ammo to reach and maintain a given level of proficiency with the greater recoiling caliber and that proficiency needs to be maintained for your entire life the price per round difference adds up. I recently fired a Shield .40 back to back with my Shield 9 and in non-ideal shooting (weak-hand only) it was obvious that my speed and accuracy were severely affected by the increased recoil.


The Winchester PDX1 is not on Dr. Roberts' list.


Some good reading about wound ballistics can be found at https://web.archive.org/web/*/http://www.firearmstactical.com (the site went down and needs to be looked up at the internet archive now.)