b & t ammo labs test #7:
Multiple round, high velocity 5.56 61.7 grain Tracer (M856) performance in bare gel.
   

introduction:


B&T Ammo Labs Fragmentation Experiment #7:

"Multiple round, high velocity 5.56 61.7 grain Tracer (M856) performance in bare gel."

Tatjana von E. and Derek W. F.

This experiment was designed as an excuse to shoot more M856 tracer under the guise of scientific experimentation for terminal performance of the round in 10% calibrated ballistic gelatin.

Note that some discrepancies in weight of tracer rounds exists. While FM 23-14 lists 63.7 grains as the weight of the bullet IMI, the manufacturer of the L-110 tracer bullet, lists it as 61.7 grains. We believe the latter figure to be more accurate.

It is probably redundant to say that the outstanding support of the AR15.com community makes this experiment possible. Nevertheless, the outstanding support of the AR15.com community makes this experiment possible. Special thanks to Eric the Ammoman who's quick delivery and excellent service meant that we have had far too many tracers for far too long. (Please slow down delivery in future to help alleviate this problem).

Also, as always, thanks to AR15.com member "Hi-Vel" for the gel molds.

If we forgot you please let us know.

   

specifics and conditions:


Ammo: 5.56, 61.7 grain Copper Alloy Jacketed tracer (L-110) rounds with cannelure. (M856).

Rifle: Pre-ban 16" Colt M4 1:7 upper on a Bushmaster lower.

Temp: 85 F
Humidity: 60%
Altitude: 215 ASL

The target was a FBI spec block (20x20x50cm) of 10% ballistic gel (9 parts water, 1 part gelatin by weight). Vyse ballistic gel was prepared according to FBI ballistic gel testing protocols. Additionally, gel temperature was not permitted to exceed 37 degrees C at any time during preparation.

Following preparation, gel was stored at ~4 degrees C and permitted to cure for 72 hours before testing. Gel was tested within 15 minutes after removal of blocks from refrigeration. Gel blocks were calibrated with a .177 caliber BB immediately before testing. (Optimum = 8.5cm @ 590 fps). Our results were within accepted calibration standards for ballistic testing without penetration measurement adjustment.
   
procedure:


10 velocity tests on the rounds were conducted using an Oehler Research 35P chronograph 15 feet from the muzzle.

After some alignment shots, targets (bare gel blocks) were placed 16 feet from the muzzle and each subjected to a single round. Velocity of the projectile was again measured at 15 feet, 1 foot before the gelatin block.

Multiple blocks were shot. We are now out of gel and have to buy a bunch more. This bothers Dr. Tatjana because gel is made from Horsies.

The blocks were examined, photographed and then dissected into slices. Slices were photographed to measure and record wound profile size. Fragments were then extracted and their penetration depth measured and recorded. Fragments were organized according to penetration depth and photographed to record fragment distribution throughout the wound cavity.

The ammunition was quite consistent in gel- but not the way you might think. Probably as a result of the length of the round, all shots exhibited a significant course deviation mid-gel and just after yaw, before exiting the side of the gel block at around 12-13"

Results notes/Observations:

Velocity of the displayed gel shot was 2954 fps.

Fragmentation of the rounds was nearly absent.

Total penetration (before exit from the block) averaged 12.5" and would probably exceed 13.5" if not for bullet exit.

Neck length (as defined by distance before a significant degree rotation of the round) was generally around 5.75-6".

The largest recovered fragments typically appear to be the bullet's base and rear jacket structures and core.

Recovered materials included 0.2gr of ash and 50.6gr of jacket/core. Given the lack of fragments it seems clear that upwards of 10gr of bullet weight is tracer element.

Wound cavity size at its extreme was a dramatic 6.3" at inch 7. This is probably the result of the unusual length of the round.

Recovered Weight:
50.8gr

Fragmentation:
N/A

Neck:
5.75”
   
conclusions:


Surprisingly the M856 does not fragment well at all. Minimal fragmentation was observed even at 16" muzzle velocity. Despite this the round does leave a rather impressive wound cavity, though it is not until deep in tissue (6-7") that the cavity opens up significantly. Accordingly, the round is not recommended for self defense applications.

Other notes and observations:

Total lack of fragmentation was extensive enough to cause Dr. Brouhaha (hee!) to dance for joy before the extraction process. Immediately after the shot he was heard to exclaim: "Ah HA!" This is generally an indicator of poor levels of terminal performance.

The orange paint used to distinguish the M856 tracer was left smeared inside the first 1-1.5" of the wound cavity. Dr. Tatjana will consult with S.P.E.C.T.E.R. about developing toxic paint coatings for future deployment.

Tracer elements appear to light IMMEDIATELY (10-20 meters) after exiting the barrel. Much past discussion about a 50-100 meter delay (including field manual notes) seems to be inaccurate.

We did not observe any scorching of the gel block, though the tracer element exited the block before coming to a rest and burning on some of the backstop material. Dr. Brouhaha will be reupping his fire insurance immediately.

Damage (temporary/permanent cavity) to the blocks were often so severe in the 5-7" range that sectional slices were hard to hold together.

Note: Neither Dr. Tatjana nor Dr. Brouhaha are Doctors of anything, they have, however, stayed at Holiday Inn Expresses.
   

figures:



Left to right: M193, M196, M855, M856, Nosler 77gr OTM


M856 High Velocity Encounter with Ballistic Gel


Recovered Fragments by Gel Depth


Fragments and Ash Close-up


Recovered Fragments (Detail)


Sectional View of Inch 5-6 of Gel
Dime Shown for Scale. Blocks 20cm in Width


Sectional View of Inch 6-7 of Gel
Dime Shown for Scale. Blocks 20cm in Width