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

[X9VlmF8m]

Given current design and manufacturing capabilities any guesses or actual studies as to the smallest projectiles that could be produced to meet standards? If so what are the limiting factors? I'm curious about both pistol (~1000fps MV) and rifle (2700-3300fps MV) projectiles.

Please note I am not asking about any particular cartridge, firearm, etc. that already exists.

[octagon]

Since the IWBA/FBI test don't require expansion and reward penetration and retained weight with little to no penalty for super deep penetration and focus on barrier "blindness" a hard non expanding projectile could pass the test pretty easily at the velocities you listed. As long as it didn't break up or was too excessively lightweight. A hard and pointy projectile is going to do better at barrier penetration at any reasonable velocity. Consider earlier armor piercing ammo for handguns.

[DocGKR]

Please define "smallest"--what physical parameter are you referenceing (mass, diameter, length, etc...)?

[X9VlmF8m]

My apologies. I see that I did not specify my question nearly as well as I thought I did and left things far more open ended than intended. I'm just thinking conventional mass producable bullets, ammunition, and semi auto firearms.

I am asking about reliably expanding projectiles and not ball or AP ammunition.

Smallest diameter. I should clarify further that the "pistol" projectile should be short enough to be fired from a conventional semi-auto pistol.
... I had implicitly assumed that the smallest mass projectile would also be the smallest diameter projectile. It's this not the case?

Thank you for indulging my curiosity.

[olstyn]

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

Admittedly I'm cherry picking here, but subsonic .300 BLK bullets are typically 200+ grains, and .308" diameter. .380 ACP @ 95 grains bullet weight is .355"/.356" diameter, so I don't think that's necessarily a valid assumption.

[DocGKR]

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

A lot depends on what the projectile is made of solid copper/gilding metal is lighter than lead core, which is lighter than tungsten core, etc...

[RevolverRob]

Everything will “expand” (read fragment) given enough velocity. I guess I’m also not understanding the question - but I think you’re asking,

“What is the smallest diameter bullet which can reliably expand, within our manufacturing abilities at present?”

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).

[X9VlmF8m]

Admittedly I'm cherry picking here, but subsonic .300 BLK bullets are typically 200+ grains, and .308" diameter. .380 ACP @ 95 grains bullet weight is .355"/.356" diameter, so I don't think that's necessarily a valid assumption.Given well designed bullets at identical velocities I believe we can say that a 90gr 7.62mm projectile would perform poorly compared to 200+gr projectiles and 200+gr .355" projectiles would out-perform 90gr .355" projectiles so your comparison isn't valid.

Due to the existence of successful .300 Blackout loads we can say that:
-- 7.62mm sub-sonic lead/copper JHP rifle projectiles that pass IWBA/FBI test standards while expanding reliably, consistently, and significantly can be designed and produced.

-- Can 7.0mm sub-sonic lead/copper JHP rifle projectiles that pass IWBA/FBI test standards while expanding reliably, consistently, and significantly be designed and produced?
-- Can 6.5mm sub-sonic lead/copper JHP rifle projectiles that pass IWBA/FBI test standards while expanding reliably, consistently, and significantly be designed and produced?
-- Can 6.0mm sub-sonic lead/copper JHP rifle projectiles that pass IWBA/FBI test standards while expanding reliably, consistently, and significantly be designed and produced?
...
At some point you hit the limit due to the inability to practically produce bullets that small, or the inability to rifle a barrel with a twist fast enough to stabilize bullets that long, or the inability to design hollowpoints that small, or simply by no longer having enough mass to meet the goal, or other constraint I haven't thought of.

What is that limit? What is the projectile weight at that limit? Is there a larger caliber that meets the goal with a lighter projectile?

[olstyn]

Given well designed bullets at identical velocities I believe we can say that a 90gr 7.62mm projectile would perform poorly compared to 200+gr projectiles and 200+gr .355" projectiles would out-perform 90gr .355" projectiles so your comparison isn't valid.

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.

[Hambo]

Please note I am not asking about any particular cartridge, firearm, etc. that already exists.

So you want theoretical ballistics on vaporware?

[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 (https://pistol-forum.com/usertag.php?do=list&action=hash&hash=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.

[Doc_Glock]

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.

The PS90 is for kids and wife. The FS 2000 or AR is for me.

[MandoWookie]

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.


Ah, I see. I was curious if it was possible to make an expanding and less velocity dependent round in something in the size range of the 5.7(i.e. something that could be put in a practically sized pistol, not an AR15 'pistol' sized platform) in line with things like the TSX and Gold Dot loadings in .223 that work better out of short barrels that don't require full length barrel velocities for good performance. Or at least something that approaches decent 9mm performance out of the FiveSeven in terms of consistent deep penetration with some expansion for tissue crushing damage like in most pistol caliber offerings, but retaining the light recoil and control you get with the smaller calibers.
Would something like a 40 grain Gold Dot soft point designed to expand at the velocities obtainable from a 5 inch pistol be able to get the required 12"-18" inches of penetration while say expanding to .30? Or is that basically impossible to accomplish?

[JodyH]

Would something like a 40 grain Gold Dot soft point designed to expand at the velocities obtainable from a 5 inch pistol be able to get the required 12"-18" inches of penetration while say expanding to .30? Or is that basically impossible to accomplish?
I'd think you'd run out of available metal or velocity before you're going to get much expansion from a 40gr. .224" diameter bullet.
Since the P90 is a straight blowback design you're not going to be able to up the velocity/pressure without blowing shit up next to your face.
I think the best way to get "expansion" out of these little bullets is a fast yaw and maybe the bullet flattens out to a slightly wider side profile.
Basically what the SS198LF does now on yaw and penetration (except they don't flatten out).

[alohadoug]

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 (https://pistol-forum.com/usertag.php?do=list&action=hash&hash=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.

You've given something to think about. I'm trying to deal with the lack of a good HD long gun. My wife and both my kids are left-eye dominant and are in the habit of shooting long guns left handed (I'm not). My wife hates the AR (thank you Army) and a shotgun is a little more than my youngest daughter is interested in. The PS90 is an option that I hadn't considered. I've found the balance on the 16" actually better than the 10". Though the 10" on full-auto was fun on the test range in Afghanistan so many moons ago. :D



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.

That's another option. Though in this Commonwealth, I think I'm limited to pre-1994 25 round magazines. :(

[Jim Watson]

Ancient history but Jeff Cooper once said of a prototype gas operated pistol, that while of no benefit to 9mm, it might make possible a Mach three .17 caliber that would "burn through" any usual body armor.
We don't have the propellants to do that now.

Could we profitably revive the .224 Boz?

[Drang]

Technical sub-forum, technical content:
OP: The bottom line is that caliber per se (i.e., diameter of projectile) does not determine terminal performance. Note that it seems to be pretty much impossible to load a .380 ACP round that is as effective a defensive round as a 9x19; the .380 ACP is also known as 9x17. A silly two millimeters shorter, and the high-end slugs will not perform.
Can you design a .22 bullet that will perform as well as HST or whatever? Dunno. I have doubts, but I am no expert on the topic.

Digression:

Ancient history but Jeff Cooper once said of a prototype gas operated pistol, that while of no benefit to 9mm, it might make possible a Mach three .17 caliber that would "burn through" any usual body armor.
We don't have the propellants to do that now.

Could we profitably revive the .224 Boz?

This reminds me of an email group I was on, the subject of some new wildcat came up, "something" necked down to take "something else". I proposed .50 BMG brass necked down to take .22 or .17 projectiles, and the list owner suggested 20mm necked down for phonograph needles...

[Jim Watson]

Yes, a common reductio ad absurdism.
The greatest neckdown I know of was the .30 Medical Museum, .30x.50, made to study the effect of shell fragments on cadavers and animals in an aimable platform.
There were also the .22x.300 Weatherby and .22x.284 Win.

The Boz was a real gun, .22x10mm in cahoots with STI and maybe Glock.
The British developers threatened legal action against Colonials making anything of the sort for other than Authorized Personnel.

See also .22 Zipperer, a neckdown of 9x23.

The present .22 TCM is a pale shadow.

[That Guy]

proposed .50 BMG brass necked down to take .22 or .17 projectiles

I could have sworn I've actually read about a .22/50, but I can't find any evidence of it right now.

Best I can come up with right now is the .22 Eargesplitten Loudenboomer: https://en.m.wikipedia.org/wiki/.22_Eargesplitten_Loudenboomer

(Bottom line is, if it sounds stupid enough, someone has probably already done it. :) )