Smallest Caliber Projectiles That Could Pass IWBA/FBI Testing? (Theoretical Question)

[X9VlmF8m]

I recognize it’s a theorerical question, but the answer is probably reflected in empirical data. The most reliable expanding bullets to date (that don’t fragment, as frequently) appear to be solid copper, pre-scored type projectiles like the Barnes bullets. In that realm, any of those bullets from approximatelt ~.30”+ in a handgun appear to reliably expand in your given velocity (1000 fps).

In the rifle realm, the .17” caliber bullets in the HMR appear to reliably expand. It is much easier to build a reliably expanding high velocity bullet. More velocity typically increases penetration and expansion - to the point of bullet fragmentation. A solid copped - Barnes-like projectile at 3000 fps would be a very good expander and penetrator, virtually regardless of caliber (though larger calibers and heavier bullets will expand and penetrate more, all else being equal).

Thank you. That is exactly the type of answer I was expecting.

I feel like you're moving the goalposts a bit with all these assumptions you didn't state in your original post. Regardless, I was merely trying to point out that diameter and mass are not necessarily tightly linked the way you seemed to think and that it's definitely possible for a long, skinny bullet to have a larger mass than a short, fat bullet.

Where did you come up with the idea that I believed that larger caliber projectiles are always heavier than smaller caliber projectiles?

I did leave the original post too open-ended allowing for non-expanding projectiles made out of expensive exotic materials that could only be produced in small quantity and fired from unconventional firearms. Other than clarifying that I was interested in conventional expanding bullets fired from conventional firearms I don't see how I moved the goal posts.

[olstyn]

Where did you come up with the idea that I believed that larger caliber projectiles are always heavier than smaller caliber projectiles?

From this direct quote from you in post #4 in this thread:

I had implicitly assumed that the smallest mass projectile would also be the smallest diameter projectile.

Edit: As for the moving the goalposts comment, I just meant how every time someone comes up with an answer you don't like, you bring up more assumptions that you hadn't previously stated which would contradict their answer.

[RevolverRob]

Let's remember one important thing that DocGKR mentioned before - mass of projectiles is as much a function of constitutional elemental density as it is length and width.

Lead has one of the highest densities per cubic-centimeter of any commonly available projectile material and one of the heaviest of commonly available elements known. Most of the remaining ones are either rare, highly radioactive, or both.

In other words, for the volume, lead projectiles will be heavier than bismuth which is heavier than copper, etc. Tungsten is about the only potential projectile material that has greater density than lead.

What we've really discovered over the last century and change of study of bullet efficacy is that mass and velocity are only part of the equation. The way a material, of a specific velocity, of a specific shape, of a specific mass interacts with a moderately (but not entirely homogeneous) mass that it strikes is fairly predictable. So, an individual can make a single bullet that is highly effective in a given set of circumstances.

But that bullet may not be able to be mass produced and/or might produce high degrees of wear may require excessive velocity, etc. OR an intermediate barrier may be introduced which complicates the world. In other words, the theory behind material properties, fluid dynamics, and interactions between theoretical bullets and objects they strike is well establish and one need only pick the right material, velocity, and shape to solve the equation. Being able to have and/or make that bullet and launch it is a whole other problem and this problem is the one that "plagues" (if you want) empirical designs from reaching theoretical peak performance.

___

That's my long way of saying, a theorist can design the perfect, effective munition, but practically you may not be able to make it.

[MandoWookie]

Slight thread diversion, but in the same vein I think of the OP's hypothetical, I've often wondered if rounds like the 5.7 or 4.6, that in their current forms available are basically novelties, could, with proper development be turned into something acceptable for civilian or law enforcement self-defense use? I'm just thinking of something like a 5.7 loaded with a purpose built Barnes TSX or Speer Gold Dot projectile that meets the FBI minimum with expansion in a PS90 with a 50 round , or a FiveSeven with its 20-30 round magazine would be an interesting combo for a light recoiling and handy PCC and pistol setup for people who might be recoil sensitive or unable to use a more conventional pistol and rifle setup for whatever reason. Add in a more EDC minded type of handgun, like a G19 or Shield equivalent in the same caliber, would seem like a good alternative( if they or the ammunition existed) to guns like the Shield EZ or LC380 that currently occupy that niche. Mainly though I'm more interested in the idea because I want to justify getting a PS90 SBR, but have it have some practical use beyond being a overly expensive .22 plinker. Being the gun to fight parasitic alien overlords and their slave army isn't justification enough unfortunately.

[JodyH]

Slight thread diversion, but in the same vein I think of the OP's hypothetical, I've often wondered if rounds like the 5.7 or 4.6, that in their current forms available are basically novelties, could, with proper development be turned into something acceptable for civilian or law enforcement self-defense use? I'm just thinking of something like a 5.7 loaded with a purpose built Barnes TSX or Speer Gold Dot projectile that meets the FBI minimum with expansion in a PS90 with a 50 round , or a FiveSeven with its 20-30 round magazine would be an interesting combo for a light recoiling and handy PCC and pistol setup for people who might be recoil sensitive or unable to use a more conventional pistol and rifle setup for whatever reason. Add in a more EDC minded type of handgun, like a G19 or Shield equivalent in the same caliber, would seem like a good alternative( if they or the ammunition existed) to guns like the Shield EZ or LC380 that currently occupy that niche. Mainly though I'm more interested in the idea because I want to justify getting a PS90 SBR, but have it have some practical use beyond being a overly expensive .22 plinker. Being the gun to fight parasitic alien overlords and their slave army isn't justification enough unfortunately.

I currently have a PS90 leaned against the wall in my bedroom loaded with 50 rounds of SS198LF (27gr. @ 2500fps). They consistently go around 12"-16" in gel and start tumbling around 5"-6" into the block. That's pretty damn effective, especially with how easy it is to put 3-5 rounds into a target super fast with zero recoil.
It's way easier to shoot under stress than any 9mm pistol for both my wife and my 16 year old boy.
I topped it with an always on Holosun HS503CU and added a Surefire X400U wml/green laser to it.
I have no doubt that's it's a far better "house gun" than pretty much any other option in my extensive collection, by "house gun" I mean a gun that any family member can pick up at any time and be effective with.
Would I be better served with my Benelli M4 and 9 rounds of FC #1B or the Steyr AUG? Probably. Would my wife be able to lay down hate with either one of those as well as with the P90? Hell no.

[Lester Polfus]

I currently have a PS90 leaned against the wall in my bedroom loaded with 50 rounds of SS198LF (27gr. @ 2500fps). They consistently go around 12"-16" in gel and start tumbling around 5"-6" into the block. That's pretty damn effective, especially with how easy it is to put 3-5 rounds into a target super fast with zero recoil.
It's way easier to shoot under stress than any 9mm pistol for both my wife and my 16 year old boy.
I topped it with an always on Holosun HS503CU and added a Surefire X400U wml/green laser to it.
I have no doubt that's it's a far better "house gun" than pretty much any other option in my extensive collection, by "house gun" I mean a gun that any family member can pick up at any time and be effective with.
Would I be better served with my Benelli M4 and 9 rounds of FC #1B or the Steyr AUG? Probably. Would my wife be able to lay down hate with either one of those as well as with the P90? Hell no.

Amen.

My wife is a twice a year shooter and that probably will never change. There's plenty of people who will scoff at her 10/22 with a 25 round magazine full of CCI-Mini Mags, but I don't see any of them lining up to let her dump the whole magazine into their chest cavity in three or four seconds.

[X9VlmF8m]

From this direct quote from you in post #4 in this thread:

... I had implicitly assumed that the smallest mass projectile would also be the smallest diameter projectile. It's this not the case?

That statement was made in the context of a thread titled "Smallest Caliber Projectiles That Could Pass IWBA/FBI Testing?" It was not a general statement applicable to all projectiles. It was a statement limited to projectiles that are at the lower limit of caliber and mass necessary to meet the goal.*

If it is the case that the smallest caliber is X (with mass Y) and the smallest mass is B (with caliber A) where A > X and B < Y then I would be surprised and very interested in why that is the case.*


* Of a given class of projectile and similar materials and construction, which should be rather self-evident.

Edit: As for the moving the goalposts comment, I just meant how every time someone comes up with an answer you don't like, you bring up more assumptions that you hadn't previously stated which would contradict their answer.

Octagon was the only one and I did not dislike his answer since it was a perfect response.

[MandoWookie]

I currently have a PS90 leaned against the wall in my bedroom loaded with 50 rounds of SS198LF (27gr. @ 2500fps). They consistently go around 12"-16" in gel and start tumbling around 5"-6" into the block.

I wasn't aware of that. I have been going by DocGKR's sticky on PDW calibers above and have not seen any testing on that load, or frankly, was I aware of its existence. What is the difference between that and the seemingly more common SS195LF? Has its performance been independently verified? I'm wondering if DocGKR has an opinion on its possible effectiveness, as rereading the sticky I'm noticing that it seems to largely be based off of military and law enforcement use, where the emphasis was on armor penetration capability first, so I assume the ammo used was the AP type leading to the lackluster terminal effectiveness? My general impression on the small caliber PDWs lack of development was due to its marketing as a way to defeat body armor better that typical SMGs or handguns, but once LE and the military realized that compact ARs had better performance both terminally and against most commonly encountered body armor basically off the shelf, that it killed any development of projectiles for the cartridges that would perform better in terminally absent the AP need. Or am I incorrect in my assumptions?

[JodyH]

I wasn't aware of that. I have been going by DocGKR's sticky on PDW calibers above and have not seen any testing on that load, or frankly, was I aware of its existence. What is the difference between that and the seemingly more common SS195LF? Has its performance been independently verified? I'm wondering if DocGKR has an opinion on its possible effectiveness, as rereading the sticky I'm noticing that it seems to largely be based off of military and law enforcement use, where the emphasis was on armor penetration capability first, so I assume the ammo used was the AP type leading to the lackluster terminal effectiveness? My general impression on the small caliber PDWs lack of development was due to its marketing as a way to defeat body armor better that typical SMGs or handguns, but once LE and the military realized that compact ARs had better performance both terminally and against most commonly encountered body armor basically off the shelf, that it killed any development of projectiles for the cartridges that would perform better in terminally absent the AP need. Or am I incorrect in my assumptions?

The SS198LF has a slight bump in velocity over the SS195LF.
Keep in mind I'm getting those velocities out of the "civilian" full length 16" barrel and I bet Doc is basing his "no-go" on the 10" LE/Mil barrel or the 5" pistol barrel.
I know out of the pistol the ammo loses 500fps velocity and only penetrates about 6"-8" (tumbles around 3"), that's not deep enough.
I would guess the LE/Mil P90 penetrates somewhere around 10" which is still a few inches short.

For US LE use there's also a bit of a stigma when it comes to hosing someone down with 10-20+ rounds out of a full-auto, and that's the way the P90 is supposed to be shot. It's not intended as a shoot 1 or 2 and assess type carbine, it's a press the trigger and keep it pressed all the way to the ground gun. I think a lot of the LE failures with the round were departments using it like a "real" carbine instead of like a sub-gun.

When we go to the range with the PS90, I take a LOT of ammo with us because every target gets 3-5 rounds (or more) every time.
One of the drills I have my wife and son do is the "1-5" which is 3 targets and you shoot T1 with 1, T2 with 2, T3 with 3, back to T2 with 4 and then finish on T1 with 5 rounds. In the end T1 has 6 holes in it, T2 has 6 holes and T3 has 3.
I encourage being generous with the 5.7 ammo.

[JodyH]

I believe the Fort Hood shooter used SS198LF in his attack.
He killed 13 and wounded 30 with a 5.7 pistol, including stopping one responding LE with a thigh and knee hit before being taken down by a second LE.
So you can't say it was only effective as an ambush weapon, he took on two 9mm armed LE in a "gunfight" that basically ended in a bit of a draw with none of the three killed.
Is the 5.7 an optimal self-defense cartridge... no.
Will it kill/stop people... yes.
Do some of its positives (like basically zero recoil) outweigh its relatively poor ballistics... I think so for semi-trained people especially.