7.62x51 Cutaways


#1

7.62x51 Cutaways

IVI/90 Tracer Short Range Training Ammo (SRTA) M974? red tip
IVI/90 SRTA M973 (AA39 in 4-1 link), 600m range, lead free copper powder in nylon matrix
T/13 Thun Switz., Tracer
FN/ 63 Duplex
FN/ * Belgian gallery, black tip (originally had no powder)
FN/ * Belgian gallery, green tip, written on side of case "400m"
What is the deal with the little “fingers” on these two projectiles? Before cutting there was 4 on each.
wolfganggross


#2

Nice sections especially the Belgium duplex - are the jackets GM or GMCS?

The CNCS bullets with the 4 plastics tails are for short range use. They splay out in flight to slow the bullet down and reduce range. I haven’t been sure of the significance of the tip color - cartridges with plain bullets also exist (I have one sectioned and will post a picture once I have time to scan the cartridge). It does look as though there are differences in bullet size and construction between the two examples you show and the one I have. This suggests that the tip color was used to identify bullet types.

NATO Dave


#3

Dave, the material is way too hard to splay out or change it’s shape in any way during flight. Also would this contradict a use with flash hiders or muzzle brakes.
The sections between the flaps are shaped with one rounded side which is influencing aerodynamics in a way where it is acting against the projectile spin and sowith is reducing the spin rate. This leads to a loss of stabilization and subsequently will make the projectile tumble and loose speed/range.


#4

The design was promoted by General Dynamics Canada called “Short Stop” and the shape “forward fins”. The fins destroy smooth aerodynamic flow around the projectile, resulting in a drag coefficient that is more than 10 times higher compared to an ordinary bullet and in the end making it loose stability, resulting in tumbling, as EOD wrote.
General Dynamics Canada advertised training usability to about 100 m and a maximum range of only 600 m.


#5

Here is the plain tipped version - bullet weight is 31.7gr. Design is different to the two bullets in the original post.

When I was told of the splaying action, I assumed that the heat and force generated in firing the cartridge would be sufficient to affect the tails. You do raise a good question about use in rifles with flash suppressors or muzzle brakes. If the tails remain in the unfired form, what is their purpose? Improved bullet stability but if so why? It’s worth noting that Belgium short range bullets (CNCS, similar bullet profile and weight) without tails exist.

NATO Dave


#6

Sorry, my error. I thought you were referring to the two leftmost bullets.


#7

Well, me too! Sorry!

But as Dave is saying now, how would that work in muzzle attachments? Damaging them or getting stripped off then. And if stripped off the fragments may leave to the side and endanger anybody around.
So this is raising the question if these tails are really splaying out. Certainly depending on the strength of the material.
Looking at other designs with plastic cores it should be sufficient to work as a short range without these tails.
Has anybody ever fired one of these and examined the fired projectile?


#8

Those are GM jacketed bullets in the duplex.
Wasn’t sure if those two Belgians were different, or if it was just me. Tails on the green were real close together, but the black tipped was much further apart.
Thanks for clarifying.
kevin


#9

Is that Belgian duplex loaded with 7.62x39 projectiles or is that my affected fantasy?


#10

[quote][quote]The CNCS bullets with the 4 plastics tails are for short range use. They splay out in flight to slow the bullet down and reduce range. I haven’t been sure of the significance of the tip color - cartridges with plain bullets also exist (I have one sectioned and will post a picture once I have time to scan the cartridge). It does look as though there are differences in bullet size and construction between the two examples you show and the one I have. This suggests that the tip color was used to identify bullet types.

NATO Dave[/quote]

[quote]Dave, the material is way too hard to splay out or change it’s shape in any way during flight. Also would this contradict a use with flash hiders or muzzle brakes.
The sections between the flaps are shaped with one rounded side which is influencing aerodynamics in a way where it is acting against the projectile spin and sowith is reducing the spin rate. This leads to a loss of stabilization and subsequently will make the projectile tumble and loose speed/range.[/quote]

When I was told of the splaying action, I assumed that the heat and force generated in firing the cartridge would be sufficient to affect the tails. You do raise a good question about use in rifles with flash suppressors or muzzle brakes. If the tails remain in the unfired form, what is their purpose? Improved bullet stability but if so why? It’s worth noting that Belgium short range bullets (CNCS, similar bullet profile and weight) without tails exist.

NATO Dave[/quote]

Dave and Alex, the original design from 1965 was supposed to have flexible flat tongues that splay out under the action of centrifugal force and thus increase the resistance of the projectile in the air. I don’t know if a projectile of this type was made.

Regarding the different colour tips and projectiles types found in these short range cartridges, I can confirm the identification of at least two variations taken from original boxes (sorry, I don’t have these at hand to take pictures):

  • Plain tip, NATO symbol FN-72 headstamp: muzzle velocity, 1300 m/s, maximum range 1000 m.
  • Light green tip, NATO symbol FN-72 headstamp: muzzle velocity 1100 m/s, maximum range 400 m.

Those two seems to be the only standardized models, as both are mentioned in a c. 1978 catalog.

Regards,

Fede


#11

Fede
Thanks for the additional information.

NATO Dave


#12

This is the cartridge that Fede had mentioned


Saludos

Sergio