Does .45 ACP Expand from a G30?

[the Schwartz]

You can look at the Lucky Gunner data provided above.

The gun is a Kahr CW45, an 'Officer Length' gun (roughly 3.5" of barrel length).

Look at the Gold Dot loadings at the bottom, 185 and 200 give excellent penetration and expansion, 230 does not.

Look at the 230-grain Ranger T, which hits 900 fps on the nose and has perfect penetration and expansion.

There are exceptions, of course, the slow 230-grain Golden Saber did just fine.

This is merely an observation on my part looking at lots of data over the years. Nothing scientific about it, really. Just one of those things where my mind that looks at a lot of trends sees something like, "Hmm, it looks like everything around 900fps tends to do what it is supposed to do."

And in the case of what I mentioned regarding weight...the thing is, you start lopping inches off of .45ACP barrels, velocity drops quickly. What was a 900fps load from a 5" gun, is now a 750 fps load from an Officer's gun. Drop the bullet weight down and you get the velocity back. All things being equal, most folks would probably prefer a 185-grain load from a small gun than a 230-grain load. Probably due almost entirely to recoil characteristics, I've found the lighter rounds in smaller guns more accurate too.

That just leads me to have a general guideline on .45 that basically says, "As you cut barrel length, reduce bullet weight. Target ~900fps +/- 50fps for optimal bullet performance. Use a quality bonded or monolithic HP round. Hit what you're shooting at."

That last point being the real key.

I'm sure @the Schwartz has some thoughts on this overall and can likely point out where my observations/assumptions are incorrect better than I can.

As always, your observations prove you to be an astute empiricist. I agree with all that you've said.

Anyone who has been involved in the shooting sports and/or reloaded their own ammunition quickly learns that when barrel length (runway) decreases, bullet mass must also decrease so that velocity can remain at a given level without exceeding the .45 ACP's pressure limit. Newton II, F = ma, says so and by extension so does E_K = mas*.

Since hydro-dynamic pressure, a direct function of velocity, is needed to drive a JHP bullet's expansion, higher velocity (within reason, of course) is always desirable. We need only to look at Bernoulli's pressure equation, P = ½ρV² , to see that the pressure (P), needed to drive the expansion of a bullet, is dictated by two variables; the density of the target material (ρ) and the velocity of the bullet (V) passing through the target material. Since velocity is an exponential variable in Bernoulli's equation, if we increase velocity by 25%, pressure increases by about 56%. If we double velocity, dynamic pressure increases by a factor of four.

Since the yield strength (which has units of pressure) of antimonial lead alloys commonly used in JHP bullet cores is typically no more than 4,000 ppsi (about 27,600,000 N/m²), using the Bernoulli equation—

P= ½ρV²

P = ½ x 1,040kg/m³ x (259m/s)² = 34,900,000 N/m² or about 5,060 ppsi

—we can see that the lower boundary, 850 feet per second (about 259 meters per second), of your recommended velocity range of 900 ± 50 feet per second guarantees that there will be plenty of dynamic pressure—and then some—to drive expansion.



About the only caveat that I might offer has to do with the validity of the Lucky Gunner test results—all of which are derived from tests conducted in a clear synthetic polymer gel product that has a much lower density than human soft tissues, water, and shear-validated 10%-concentration ordnance gelatin. Unfortunately, the density of the synthetic gel product also varies from 790 to 824 kg/m³ due to the manufacturer's constant and unpredictable reformulation of their product. The synthetic gel product's much lower density produces less dynamic pressure than a bullet would encounter while traversing human soft tissues (which has densities ranging from 950 to 1,070 kg/m³), water, and 10% ordnance gelatin. In terminal ballistic tests conducted using the synthetic gel product, bullet expansion is under-represented and maximum terminal penetration depth is over-represented as it would occur in human soft tissues and the other soft tissue analogs. Several independent researchers have confirmed this issue and the fact that the synthetic gel product does not properly shear-validate like 10% ordnance gelatin.

That matter aside, Rob, I think that your observations are right on target—pun very much intended.


*This has nothing to do with my friend @Mas.

[RevolverRob]

Okay, thanks. I do understand the basic concept of reducing weight to increase velocity and the role of velocity in expansion. I had just never heard the .5" / 20 grains thing. My position has generally been that below about 4", .45 ACP is not the best choice of caliber.. I have never heard positive things about the performance of bullets lighter than 230, with the exception of some of the all-copper bullets, but things change and I am sometimes behind the curve. The .5" /20 grains thing was new to me and there may be more recent ammo selections that change that, so I was curious.

It has been years since I carried a .45 for work or defensive purposes although I have a few around and enjoy shooting them.

I think your general observation that .45 was sub-optimal in <4" guns in the past is absolutely correct. And I suspect it is because there was a dearth of reliable guns in that size range. For a long time you had your choice of an Officer's 1911 or nothing and a poorly built Officer's gun is sort of like nothing... Only with the Glocks, the USP Compact and HK45C do we have really reliable guns in that size range. And then the bullet performance seemed to follow once people took that size range seriously.

If someone wants to shoot and carry a G30, I'm all for it. If I were carrying one, I'd probably choose the 185-grain Barnes loading and drive on. But I wouldn't lose any sleep if I had it loaded with the same 230-grain HSTs that I have in my 5" 1911 right now.

[jd950]

—we can see that the lower boundary, 850 feet per second (about 259 meters per second), of your recommended velocity range of 900 ± 50 feet per second guarantees that there will be plenty of dynamic pressure—and then some—to drive expansion.

I doubt that a particular velocity "guarantees" expansion due to a mathematical formula or law of physics. The theories and formulas are fine as far as they go but there are just too many variables in the real world, including bullet design and construction, based on my experience and training. I am quite sure one could easily design a hollowpoint bullet with unreliable expansion even when driven to a velocity at which, in theory, expansion is guaranteed. In fact, I am pretty sure that has been done several times And, as a bullet gets lighter and faster to increase the liklihood of expanison, adequate penetration may become compromised. I like to rely on a combination of testing in proper gel coupled with real world feedback on performance. In any event, I would tend to follow this:

DocGKR: "In .45 Auto barrels under 4" or so, I'd also likely choose a Barnes all copper 185 gr +P loading. Barrels 4" and longer, I'll stick with a good 230 gr loading."

Barnes XPB 185 gr JHP (copper bullet)
Hornady Critical Duty 220 gr +P JHP
Federal HST 230 gr JHP (P45HST2)
Federal HST 230 gr +P JHP (P45HST1)
Federal Tactical 230 gr JHP (LE45T1)
Speer Gold Dot 230 gr JHP
Winchester Ranger-T 230 gr JHP (RA45T)
Winchester Ranger-T 230 gr +P JHP (RA45TP)

[jd950]

I think your general observation that .45 was sub-optimal in <4" guns in the past is absolutely correct. And I suspect it is because there was a dearth of reliable guns in that size range. For a long time you had your choice of an Officer's 1911 or nothing and a poorly built Officer's gun is sort of like nothing... Only with the Glocks, the USP Compact and HK45C do we have really reliable guns in that size range. And then the bullet performance seemed to follow once people took that size range seriously.

If someone wants to shoot and carry a G30, I'm all for it. If I were carrying one, I'd probably choose the 185-grain Barnes loading and drive on. But I wouldn't lose any sleep if I had it loaded with the same 230-grain HSTs that I have in my 5" 1911 right now.

No, I feel a .45 in a short barrel is sub-optimal even in a reliable gun. In a short barrel with factory ammo, and for defensive/L.E. purposes, the performance .45 ACP round suffers too much, IMO. I assume anyone carrying a 3-3.5" barrel gun is doing so for defensive or LE purposes. Most factory ammo from such barrel lengths just does not reliably perform at an acceptable level for me. To the extent one can counter this with hotter ammo, new issues arise with recoil, muzzle blast, etc. With homebrew ammo, that may not be true, or as true, but relatively few people reload, and in LE circles, it just isn't done.

If I were carrying a .45 in a 3"-3.5" barrel, and had the choice, yes I would carry the all-copper Barnes, and I even have some around here somewhere. But before doing that I would carry a 9mm. Don't get me wrong...if someone handed me a 3" barrel .45 with factory ammo and said it was to be my defensive gun, I would not break down in tears or refuse to carry it, and most likely, if used, it would do what is needed. But if I want a .45, I carry a bigger gun better suited to the caliber. I have at times in the past carried the P220 Carry and a S&W 4516, but that is about as small as I would go, and I would prefer a 9mm in that size range. I realize saying anything negative about the .45 ACP is heresy to many and my comments above may invite "then you stand downrange and let me shoot you with my 3" .45 and we'll see how weak it is" comments, but PF is one place where I can probably get away with saying this stuff. Hopefully.

[the Schwartz]

I doubt that a particular velocity "guarantees" expansion due to a mathematical formula or law of physics.

You've mischaracterized what I actually stated.

I never stated that a particular velocity guarantees expansion due to a mathematical formula or physical law.

This is what I stated:

Since the yield strength (which has units of pressure) of antimonial lead alloys commonly used in JHP bullet cores is typically no more than 4,000 ppsi (about 27,600,000 N/m²), using the Bernoulli equation—

P= ½ρV²

P = ½ x 1,040kg/m³ x (259m/s)² = 34,900,000 N/m² or about 5,060 ppsi

—we can see that the lower boundary, 850 feet per second (about 259 meters per second), of your recommended velocity range of 900 ± 50 feet per second guarantees that there will be plenty of dynamic pressure—and then some—to drive expansion.

I stated that Bernoulli's law ''guarantees that there will be plenty of dynamic pressure to drive expansion" and never made any claim that the resultant (and plentiful) pressure would guarantee expansion. Whether or not a JHP expands in the presence of adequate pressure is another matter altogether that I didn't address. The fact remains that, at the quoted velocity, according to Bernoulli's law, there is sufficient pressure to drive expansion if it exceeds the yield strength of the bullet's lead alloy.



If, on the other hand, you are claiming that Bernoulli's law is somehow unsound, please explain why and how you came to that conclusion.

[jd950]

You've mischaracterized what I actually stated.

I never stated that a particular velocity guarantees expansion due to a mathematical formula or physical law.

This is what I stated:

I stated that Bernoulli's law ''guarantees that there will be plenty of dynamic pressure to drive expansion" and never made any claim that the resultant (and plentiful) pressure would guarantee expansion. Whether or not a JHP expands in the presence of adequate pressure is another matter altogether that I didn't address. The fact remains that, at the quoted velocity, according to Bernoulli's law, there is sufficient pressure to drive expansion if it exceeds the yield strength of the bullet's lead alloy.

If, on the other hand, you are claiming that Bernoulli's law is somehow unsound, please explain why and how you came to that conclusion.

My apologies if I misunderstood what you were saying. That is why I bolded the part I was talking about. It appeared to me that by stating "guarantees that there will be plenty of dynamic pressure—and then some—to drive expansion" you were suggesting that expansion was assured by velocity alone and were failing to consider bullet design and material, the nature of what the bullet strikes, intermediate barriers, etc. It still looks that way to me, but I am probably still misunderstanding you.

I do not claim that Bernoulli's law is unsound. I don't actually know or care enough about Bernoulii's law to have an opinion. My understanding is that "Bernoulli's law describes the behavior of a fluid under varying conditions of flow and height." So that gives me pause. But more to the point, I don't think Bernoulli's law or other theoretical physics or math concepts are particularly useful to the issue of terminal ballistics and selecting defensive guns and ammunition.

But, if you and Bernoulli are happy carrying a .45 with 200 grain JHPs, then that is okay with me and I wish you both well. Well, you anyway; Bernoulli is a bit past his sell-by date.

Meanwhile, I am off to perform some fluid dynamics experiments with a nice glass of whisky since I am not on-call tonight.

[MGW]

Is it weird that I read this entire thread and my only take away was “I need another HK in 45 in my life.”?

[the Schwartz]

My apologies if I misunderstood what you were saying. That is why I bolded the part I was talking about. It appeared to me that by stating "guarantees that there will be plenty of dynamic pressure—and then some—to drive expansion" you were suggesting that expansion was assured by velocity alone and were failing to consider bullet design and material, the nature of what the bullet strikes, intermediate barriers, etc. It still looks that way to me, but I am probably still misunderstanding you.

I do not claim that Bernoulli's law is unsound. I don't actually know or care enough about Bernoulii's law to have an opinion. My understanding is that "Bernoulli's law describes the behavior of a fluid under varying conditions of flow and height." So that gives me pause. But more to the point, I don't think Bernoulli's law or other theoretical physics or math concepts are particularly useful to the issue of terminal ballistics and selecting defensive guns and ammunition.

But, if you and Bernoulli are happy carrying a .45 with 200 grain JHPs, then that is okay with me and I wish you both well. Well, you anyway; Bernoulli is a bit past his sell-by date.

Meanwhile, I am off to perform some fluid dynamics experiments with a nice glass of whisky since I am not on-call tonight.

No problem. This sort of stuff (the math, applied science, etc.) isn't everyone's cup of tea. Or whiskey.

There is a lot more to Bernoulli's law than flow and fluid column height as Bernoulli's law can be modified to predict/model armor penetration much like Alekseevskii and Tate did in the mid-1960s when they modified it to model the projectile-target pressure interface gaining quite a bit of acclaim in the field of study. That'd probably bore the dickens out of you, too, given your disinterest/lack of regard for such things so I'll leave it at that.

[the Schwartz]

Is it weird that I read this entire thread and my only take away was “I need another HK in 45 in my life.”?

No.

Doesn't everyone need another HK in .45 in their lives?

[Glock17JHP]

If you have either firearm--the Glock 21 or 30--and a few JHPs that you're willing to sacrifice for the cause, you can always fire a few into water (an inexpensive, yet perfectly valid soft tissue simulant) to see if they will expand when fired from either pistol. Water is an "optimal conditions" simulant so if the JHPs won't expand in water, they probably won't expand in soft tissue either. If the only performance attribute you are seeking is to see if expansion will occur after impact, there is no need to collect any additional data to model terminal penetration depth and permanent wound mass/volume.

Great advice... that's exactly what I did soon after joining the IWBA. The data I generated was good enough to be accepted in the IWBA journal. You can always do your own testing. Suggest 4 feet deep minimum on the water, and a plastic sheet over the top to control splashing.