A rifle round’s effectiveness depends on its crack & splash

Saturday, April 13th, 2019

A rifle round’s effectiveness depends on its crack & splash, Emeric Daniau explains:

In the first report, the acoustic and visual signature of several rounds are compared, including the XM645 “flechette” round fired from the XM19, the 5.56 mm M193 fired from the M16, the 7.62 x 39 mm fired from the AK, the 7.62 x 51 mm fired from the M60, the .45 ACP fired from the M1A1 SMG and the .50 BMG fired from the M2 HMG.

Those results will serve to identify physical parameters that could be used to build a relative scale for suppression, accounting for both acoustic and visual stimuli.

Results from the second report will be used to correlate this relative scale to real life “threatening” distance.


Live fire test performed at a distance of 150 m revealed that:

  • the mean dangerousness of both the XM19 and the M1A1 SMG were rated significantly lower than other weapons, the XM19 being rated significantly lower than the M1A1,
  • subjects failed to discriminate the AK from the M60, and the AK from the M16 (“From Table 5-14 it can be seen that only the comparisons of the AK47 with the M60 (+0.16) and the AK47 with the M16 (+0.23) fail to reach the ICI of 0.38 necessary for the demonstration of a significant difference in the mean perceived dangerousness for the two weapons”), but the difference between the M16 and the M60 could be considered significant (a ICI of 0.39 was achieved between those two weapons).
  • the .50 BMG scored the highest mean dangerousness value, but the result was not found “off scale” compared to other weapons,
  • mean dangerousness decreased linearly with the miss distance (minimum miss distance considered was 2 m).


Again, live fire tests performed at a distance of 150 m revealed that:

  • the M1A1 SMG in the visual signature mode received a higher mean suppression scale value than did the M16,
  • the visual effect of the .50 BMG M2 HMG was so much “off the scale” compared to other weapons that it was not possible to find a statistically significant difference between the M1A1 SMG, the M16 AR and the M60 MG (the XM19 was not rated).

It was anticipated that the visual signature of impacting bullets would be related to kinetic energy (because cavity volume in soft soils is directly a function of the kinetic energy), but the rating of the M1A1 SMG over the M16 suggests that other mechanisms could be involved.

This unexpected observation could be linked to the ricochet characteristics of those very different bullets, a low velocity.


For the 7.62 mm, a miss distance around 6 m will produce 50% of suppression, compared to around 3 m for the 5.56 mm and the .45 ACP, and 24 m for the .50 BMG (a class of its own, and ~4 times the miss distance of the 7.62 mm).

Presented differently, at a (presumed) distance of 150 m a single 7.62 mm NATO (24 g cartridge) could be expected to supress 50% of a group located in a 113 m² area, compared with 28 m² for the .223 Remington (12 g cartridge) and 1,800 m² for the .50 BMG round (115 g cartridge).

So, if we divide the suppression area by the cartridge weight, we found that at a distance of 150 m, 1 kg of .223 Remington ammunition will provide a 50% suppression effect in a 2,350 m² area, 1 kg of 7.62 mm NATO ammo will cover 4,710 m² (twice as much for the same ammo load) and 1 kg of .50 BMG will cover 15,700 m².

The miss distance for achieving suppression 90% of the time is much shorter, around 0.7 m for the 7.62 mm NATO, less than 0.5 m for the 5.56 mm and the .45 ACP, and 5 m for the .50 BMG (again, a class of its own in the realm of kinetic energy small-arms).


  1. Kirk says:

    Oh, there’s a whole dissertation to be written on this subject…

    First, though… What Daniau is discussing here is the effectiveness of the projectile in purely psychological terms. You may fear a round that really isn’t that effective in terms of “Will it kill someone…”, and do so because of the signature it generates. You don’t get a signature, there’s nothing to fear.

    I recall being on a range, once, doing repair work on part of the targetry setup. My guys and I are scattered about the jobsite, doing our thing, and I notice these little puffs of dust that are happening all around us. I’m occasionally not all that bright, and since I “knew” that Range Control knew we were out there, it never occurred to me that the idiots might have gone ahead and opened up the MG range that was in front of where we were working.

    They really were that dumb. So, even though we all “knew” that the rounds falling all around us were deadly, being .50 cal, nobody paid even the slightest attention to them. For about five minutes, and then it dawned on someone that, holy shit, we were being shot at!!

    Cue the psychological effects, and about twenty guys trying to clamber under the one truck still on the jobsite (the rest were hauling materials for the project…) Also, cue frantic radio messages to the nice people at Range Control and/or whoever was on the range. This was when we discovered that our radio had gone out, and oh-by-the-way, the secondary phone line was also not working…

    Things like this are why I have my doubts about the advisability of widespread issue of suppressors. The noise we generate with weapons is at least as important as anything else, and I suspect that a big reason why the bow was supplanted by the primitive guns of the early days had as much to do with the salutary psychological effect of making a big noise back at the bad men attacking you… It’s magic, see? That arrow is more-or-less silent, comparatively. Fire the arquebus, and that’s a huge morale boost. Not to mention, who the hell wants to go charging a formation full of those damn things…?

    The psychology of it all is an important component to the whole thing, as well as the learned response to the effects of the weapons. You want effects, they better have identifiable signatures.

    It’s one reason I’m so damn dubious about the XM-25 after-action reports from Afghanistan. Those basically consisted of “We took fire from yon hillside; we returned fire with XM-25; fire ceased. XM-25 work good.”. Reality? You don’t know why fire ceased–Maybe there were five dead Taliban clustered around that PKM, maybe they ran out of ammo coincidental with the firing of the XM-25, or maybe, just maybe, they went “Huh… That’s weird… What the hell did they just fire at us…? Let’s get out of here before something weird happens…”.

    There’s way, way too much magical thinking around a lot of this crapfest we call the “art and science” of military small arms. Daniau is trying hard to try to come to terms with all the variables, but the utter lack of real data out there is where the effort fails. For one thing, you’ll note that Daniau does not differentiate between trained veteran professionals and their responses to fire, vs. the untrained masses who are coming under fire for the first time. Ya don’t know what you’re hearing or seeing, and you’re not expecting it? Yeah; precisely zero psychological effect gets generated.

  2. Lu An Li says:

    The Paris gun also had those rounds descending from what was nearly outer space, the origin of which could not be determined. The French thought the rounds were being dropped from a high-flying airplane. One American aviator got so high in the search for the mysterious German warplane the man lost control and crashed.

  3. Paul from Canada says:

    This is fascinating stuff.

    To be “suppressed”, you need to KNOW that you are under effective fire. I recall in training that missing low/short was actually desirable. The round might skip and hit anyway. If it did not, it would still kick up dirt in his field of view, distracting the enemy, and if the misses were close enough, scaring him (suppression).

    If rounds are missing high overhead, well off to the side, or if they are far enough away that the sound of rounds passing is lost in the sound of your own firing, you will ignore it. If it snaps just past your ear, or throws dirt in your face, you will not.

    Kirk’s statement about the psychological effect is
    spot on. That is almost exactly why the firearm supplanted the bow (that and cost and training time), and the psychological effect works both ways, i.e. making a big scary noisy display helps the shooter feel better, as much as it discomforts the enemy. Similarly the effectiveness of the bayonet or cavalry charge.

    Most combat is ultimately psychological. One side breaks and retreats, often long before they suffer catastrophic levels of casualties. If you look at a lot of engagements, the losers lose only around 10% or so, and retreat either because their position is untenable (due to the maneuvering of the enemy), or because, they (or most importantly, their leader) loses confidence.

  4. Kirk says:

    This was the essential brilliance of the German MG doctrine, which really meant “Most of German infantry minor tactics”.

    Based on the “strategy of surfaces and gaps”, the essence of the idea was to dislocate the enemy from his prepared defenses; get the psychological advantage on him, force him to behave as you desired him to. The rate of fire on the MG34/42 families were deliberately chosen at least partially because of that psychological effect–Imagine being set up in a defense, and waiting for the onslaught, and then taking that volume of fire from one of your rear flanks… Most troops are going to break-and-run, probably right into another prepared fire sack.

    It would have been interesting to see what would have happened with the Germans going up against another opponent who was at least fully cognizant of what the German infantry was trying to do. They never really did, but I can imagine that were you to attack into the German lines along similar “surfaces and gaps”, instead of withdrawing…? You might just have discombubulated them, rather effectively. Just like the way the solution to being ambushed is to turn into the ambush and attack, perhaps the way to overcome the German predilection for maneuvering their guns into your rear would have been to take the opportunity to “go deep” into his own depleted lines while his elements were in your rear.

    I don’t think anyone ever really tried that, though. They mostly just let the Germans do their thing, and reacted, mostly ineptly. Does make you wonder–What would have happened, had the German infantry ever faced a really competent enemy who understood the game they were playing…?

  5. Alistair says:

    +1 for psychological effects.

    I think early firearms win-out because they are a cheaper way to generate killing power. half-trained peasant + arquebus ~= trained bowman. However, one mustn’t discount the psych bonus as well. Not good for horses too.

    (It helps that the gun is better against armour, even if the bow is better against light armour and ranged targets. You can store the guns and raise the rabble easily. Trained bowman require constant expenditure.)

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