Intentional Range Reducing Design Features In Ammunition

General Ammunition Discussion
#1

As a collector of INERT, tank fired discarding sabot ammunition I have always been amazed and the different types of engineering concepts and science that goes into some of the 105MM and 120MM target practice ammunition to intentionally reduce the projectiles range. Since most tank practice ranges are too short to safely fire tactical ammunition, the majority of target practice tank ammunition is designed to become unstable around 2000 meters and to fall to earth at a safe distance.

This range reduction is the result of some ingenious engineering concepts, the ones I am aware of I will list below. I am curious, are there any other “Range Reducing” design features used in other types of ammunition?

Jason

The most common range reduction design feature used on tank fired ammunition is the “Cone Stabilization Assembly”. Instead of using fins to stabilize the sub-projectile in flight, this type of ammunition used cone stabilizers with precisely drilled holes, ports or fluted grooves manufactured in them to reduce overall distance. This aerodynamic principle is called the LKL Principle or “LochKegelLeitwerk” effect. The holes, ports and grooves in the cone assembly are aerodynamically “open” at extreme speeds. Over distance when the sub-projectile slows, these holes, ports or fluted grooves are aerodynamically “closed” and an engineered distance. This increases drag and the sub-projectile becomes unstable and falls to the ground.

Some Typical 105MM & 120MM Cone Assemblies Utilizing The LKL Principle FOr Range Reduction

FLUTED GROOVES

This is the US XM797105MM TPFSDS-T (Target Practice FIN Stabilized Discarding Sabot Tracer) projectile. It does not relay on the LKL Principle to reduce its range. Instead super genius engineers came up with this amazing design. They created a “SPLIT APART” sub-projectile. The XM797 has a sub-projectile dart that is split longways down the middle on its longitudinal axis. The two halves of the projectile are sandwiched together and an aluminum fin assembly is attached for stabilization. At the very tip a specialized zinc alloy windscreen is added creating a seemingly solid, well-held together sub-projectile. The way this results in range reduction is amazing. After being fired and the sabot discards, the sub-projectile screams down range at blistering speeds. Over a known distance, the zing alloy nose cap fails due to aerodynamic heating and centrifugal forces which cause the sub-projectile dart to split apart and tumble to the ground with-in a known distance.

Photo of the XM795 showing its specialized zinc alloy windscreen/nose cap. If you look carefully, you can see the line showing the split.

XM797 with windscreen removed

XM797 in flight

XM797 broken down

This is one of my favorite range reducing designs. The Israeli IMI and German Diehl companies combined efforts produced the CL-274 or DM-148 105MM TPFSDS round. This round uses 4 pyrotechnic time delay charges placed inside the sub-projectile dart. t a known distance, these charges blow causing the sub-projectile to break in half an engraved separation point.

Anyhow, are there any other types of ammunition, larger or smaller then tank rounds that purposely utilize a “Range Reduction” design feature?

#2

I’ve seen 50cal bullets that had a “finned” section where the boat tail would normally be, this was intended to destabilize the projectile by slowing/stopping it’s rotation.

#3

Here is some 5.56 and 7.62 NATO rounds from NAMMO and General Dynamics (IVI). They also make some .50 BMG ammo… but I cant find the doc’s at the moment.




#4

There’s the Belgian “Airflap” 9mm loads with the plastic or metal fins meant to limit their range so as to reduce collateral damage. They were one of the most complex projectile designs for a 9mm (from Lew’s introduction to 9mm collecting file):

#5

Fantastic! These are all examples that I was hoping to learn about. That 9MM with built in flaps is amazing. The Namo ammunition with fluted projectiles is great. Looks like it may utilize the LKL principle also? Hopping there are more examples of range reduction methods in other ammunition. So cool!

Jason

#6

Interesting thread, thanks for starting it APFSDS! Hereby some contributions.


gd-ots.com/2011%20Brochures/ … 20LRTA.pdf

.50 BMG Limited Range Training Ammunition, made by General Dynamics Ordnance Tactical Systems.


Small collection of Plastic Traning cartridges. FLTR: .32 ACP, 9x19, .30 M1, 7,62x51 (ball & tracer), .50 BMG (ball & tracer)

#7

That .50Cal projectile is so cool. I love the science that goes into ammunition and all of these different ways to intentionally reduce range is amazing. I wonder how many examples and methods are used in other types of ammunition.

Jason

#8

There are other oddball pistol projectiles which had range control in mind just by the material the bullet was constructed of. The Equalloy bullets were made of aluminum and meant to have very high velocity at close range, and then drop off rapidly after short distance. Geco and American Ballistics also tried some aluminum bullets with the same thing in mind, and you can trace most of this type of bullet to things deemed “anti-skyjack” which was sort of a fad in the 80’s, and then again after 9/11, but mostly as a frangible endeavor. A modern version would be the Liberty Ammunition “Halo Point” that is made of tin / aluminum and has a very high velocity at realistic engagement distances, but which drops off rapidly after 100 feet or so.

#9

I think there is a treatment of the GD M973 7.62mm short-range round scheduled for inclusion in an upcoming IAA Journal issue. The wooden-core jacketed bullet for the Danish Schouboe Model 1907 pistol cartridge was very lightweight, and therefore was limited in its effective range. However, the intent was more so that the pistol could be of blowback design, and not so much for range limitation.

#10

I remember when I used to live in an apartment where are the units were seperrated only by drywall. Due to this, I bought some type of 9MM ammunition that had a super light projectile and a hot charge. The projectiles were hollow points filled a few balls then covered with a see-through resin. I was told that they were very effect at close range and because the projectile was so light that the range was reduced, especially after hitting something. Not sure if a hot charge combined with a light projectile counts as intentional range reduction? Nothing like those 9MM’s DK posted which are amazing.

Jason

#11

You’re describing Magsafe ammo with the pellets & resin, and those were advertised as being somewhat frangible and safe for not over-penetrating walls in the way that normal projectiles would. They are still sold today in multiple calibers in the “Swat” version, and the classic “Defender” version. There used to be something like 12 other versions when inventor Joe Zambone was still alive.

#12

The .38sp Thunderzap (plastic HP bullet) is another pistol-cal round with reduced range touted as a design feature. Unfortunately, a vast majority of light-for-caliber defensive loads in pistol and rifle cartridges (MagSafe included) do not exhibit adequate terminal penetration (12"+). No free lunch.

The plastic practice rounds for my agency’s 40mm less-lethal launcher (both from Deftec) exhibit the same holes as the LKL tank projos pictured; no rear cone or moving parts however.

#13

DK, that’s was totally it, the were definitely called Magsafe rounds. Thank you, that would have drove me nuts trying to remember.

Mwinter, that is so cool that your 40MM LTL rounds incorporate the LKL method of range reduction. This is something I have never heard of before. If you ever get a chance, I would love to see a photo (If Possible).

Jason