Assume two identical 9mm JHP projectiles, both expand to .65", and both penetrate 14" in ballistic gelatin but one has a MV of 900FPS and the other has a MV of 1200FPS. Does the faster load offer any terminal ballistic advantage?
Basically, if a bullet has a very wide expansion window, is their any advantage to driving it faster?
This question only applies to handgun rounds not rifle rounds.
I guess that depends on what velocity the bullet was designed for. For example, we can take a solid performing 147gr bullet at standard pressure from a 4.5 barrel nd get great results. Now, we use a +P version of the same bullet and the petals fold back on themselves, causing a smaller diameter and deeper penetration, possibly exceeding the 12"-18" that is ideal.
Generally speaking, if they were the exact same bullets and it performs best at 900fps, adding 300fps will likely make the bullet less effective by folding the petals back on itself and over penetrating, as would a bullet designed for 1,200fps and slowing it to 900fps. In that case, it might not open enough and will likely under-penetrate.
The way you presented the question there is only one correct answer is: No, the is no advantage to driving it faster, from a terminal ballistics perspective, in bare ballistic gelatin.
However, there might be other differences in performance, expansion and penetration against auto glass, denim, soft body armor, other barriers, et al, that your instant case does not address.
Also there are a ton of marketing and profit opportunities for the ammo maker, to make and market and profit by producing two different velocity rounds, with “identical” terminal performance.
The question you are asking can be addressed by using a mathematical bullet penetration model.
Fortunately, there are two such models (the Schwartz bullet penetration model found at: www.quantitativeammunitionselection.com and the MacPherson bullet penetration model found at: http://www.amazon.com/Bullet-Penetration-Modeling-Incapacitation-Resulting/dp/0964357704 ) that can be used to explore the terminal ballistics question you’ve asked.
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No, even at 1200fps the velocity is still too low to create a significant temporary stretch cavity.
Also throwing that bullet at a higher velocity will increase the recoil and make follow up shots slower. So if they perform exactly the same at either velocity I would rather have the slower load.
To throw a bit more information out there here is the practical question I’m asking. Speer 124gr Gold Dots expand reliably down to roughly 750FPS according to the ATK ammo experts. The +P loading has a MV of roughly 1220FPS out of a G19 and 940FPS out of an MP5SD. The standard pressure version has a MV of roughly 1170FPS out of a G19 and and 830FPS out of the SD.
Since all of these loads/platforms show very, very close results in ballistic gelatin (expansion, penetration, etc) are they all as effective terminally since pure velocity seems not to add much or anything at handgun cartridge velocities?
Have some modern bullets, with wide expansion thresholds, finally allowed the SD to match the terminal ballistics of those same rounds fired out of handgun or regular MP5?
Additionally, other 124gr +P loads retained 1040FPS out of the SD. While the expansion threshold of this round isn’t yet known, if it is similar to the 750FPS threshold of the GD is there any benefit?
When does it start to expand with each round? How deep does it go before starting to open up?
Good question 
Advantages of higher velocity rounds is longer effective range, flatter trayectory, and better performance against most intermediate barries.
I would like to know about the short range differences, if any.
Even if the difference in temporary cavity is relatively small between 900 (or even 750) fps and 1200+ pfs, I would go with the higher velocity rounds in my handgun because I don’t find them difficult or slow to shoot or abusive to the gun. Many handguns actualli LIKE rounds with plenty of recoil impulse for reliable function. And a bit of extra temporary cavity does not hurt the shooter but may very well hurt the recipient a little more if the round impacts close to an organ with inelastic tissue.
Given that you’re not pushing the bullet too fast, and therefore screwing up its expansion, the obvious advantage of speed would be range. The faster bullet will go farther before falling below the expansion threshold.
There may be other advantages as far as barrier penetration, but I’m not an expert on those, so I’ll leave it to others who know more to say.
Although referencing the 45-70, the same effect may be present with other calibers?
I know when we get into hard cast/solids, etc with rifles or even high energy pistol, a through shot at x speed is the same as a through shot at a higher velocity. That point was made for people wanting as an example 1500 fps with a certain bullet when the same fully penetrated at 1100 fps within specified hunting range-what’s the gain?(other than recoil)
At least until the recent past, Randy Garrett prime testing material was good 'ol water saturated newspapers…
In my admittedly unique situation with the MP5SD the only advantage to greater velocity is greater range. The 124gr Gold Dot +P retains 830FPS at 110 yards and estimated minimum expansion threashold velocity of approximately 750FPS at 200 yards. Comparatively, the 124gr Dold Dot standard velocity has a muzzle velocity of 830FPS and reaches the approximate expansion threashold of 750FPS at about 100 yards. Since the SD actively “robs” about 200FPS the +P round seems justified in this instance. Since the maximum effective range of the SD, because of trajectory issues, is about 100 yards it’s nice to have that extra 100FPS “buffer” at 100 yards with the +P vs being right at the bottom of the threashold at 100 yards.
That all said, considering the systems maximum effective range of 100 yards, would a muzzle velocity of 1040FPS buy me anything extra? I can’t seem where it would.
This is specific to the 124gr Gold Dot projectile. The Winchester Ranger 124gr Bonded +P retained 1040FPS muzzle velocity in the SD but yielded almost imperceptible expansion at the the very tip of the projectile with no gain in diameter. Clearly some bullets do well at moderate velocity while some have to be driven pretty fast to work.
I spoke with DocGKR yesterday and he agreed that modern projectiles, properly selected, make the MP5SD just as effective as the standard MP5 shooting 200FPS faster.
In pistols, I wouldn’t hesitate to use a slower, non +P load with proper bullet selection. I use the 124gr Gold Dot +P only because it perfectly mimics the POI of the NATO ball that I use as a practice round. M882 chronographs almost identically to the 124gr Gold Dot +P out of pistols, SMGs, and the SD.
David, if you shoot through car doors (or other barriers) perhaps the 200 fps would make a difference.
I think in normal pistols and SMGs fitted with add-on supressors the ideal load would be a subsonic 147 gr JHP.
Is there any advantage in using an integral suppressor that bleeds pressure and velocity from the barrel?
How does extra velocity help penetrate barriers? Several people have said this in this thread.
Not challenging, just asking. (I know text doesn’t convey tone.)
Thanks!
As noted above, in the situation described, I’d definitely use the 124 gr +P Gold Dot; also nice that M882 works as a good training round.
For stuff such as metal sheet/thin plates, penetration is a function of energy delivered per impact area. Given a tough bullet design that does not disintegrate easily at normal handgun impact velocities (such as the ones we are discussing now), more velocity = more impact energy = more penetration. Anyone can test this.
For stuff such as bricks, cinder blocks, etc. it is more iffy, because with these material even tough bullet break up a lot. Perhaps a higher velocity bullet may blow a bigger chunk of material but do not penetrate more.
Regarding wood/timber, a higher velocity bullet also penetrates more. But it is more iffy with JHPs compared to FMJ.
Now glass is a tough barrier, specially windshields, and even premium JHP may have problems with it at high velocity. I don’t have enough experience with this material, or drywall, or laminated wood, perhasp someone else can chime in.
I would think momentum would be more important than energy in this case. Momentum is a product of inertia (an object’s resistance to change in motion, in this case its resistance to deceleration) and velocity. Since momentum increases with velocity, so should penetration if everything else is kept constant (such as expansion and fragmentation).
In any kind of a junkyard test, all hard barrier type materials require a higher impact energy to punch through them. This is referred to as a “piercing” effect. Sheet steel is one such material where higher velocity is essential for piercing. Smaller calibers can pierce hard barriers better because their impact energy is concentrated on a smaller impact area. In fact, armor penetrator loads have a pointed bullet nose which aids in piercing due to a very small impact area.
As a general combat load, in my opinion there is no disadvantage in using the middle weight bullet at higher velocity(9mm 124gr+P, .40S&W 165gr, .45acp 200gr+P) if you want your bullets to have the best all around barrier defeating ability, while still maintaining ideal terminal effects.
ENERGY!