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Military Guns and Ammunition

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This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons.

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Neckless ammo   Ammunition <20mm

Started 20-Aug by EmericD; 13322 views.
gatnerd

From: gatnerd

22-Aug

EmericD said:

Bullet jump on this round should be similar to bullet jump with a CT ammo, that should be OK. Not match accuracy, but when I used AB Analytics and the methodology found in the "Hall report" (BRL-MR-593) to compute the hit probability at 600 m, I din't see a significant effect of the bullet dispersion (1, 2, 3 or 4 MoA gives roughly the same hit probability).

If it turns out they can be used in unmodified weapons, that will be a real game changer. At that point if would make sense to just go neckless as standard issue when converting to polymer cases, rather then even bothering with a polymer 5.56. 

The bullet jump being comparable to CT/LSAT ammo is interesting. I wonder if that means they are also comparably ~3moa? 

I'm surprised the differences between 1-4moa had such minimal effect on hit probability. I guess drop, wind drift, and shooters error are more of a factor at those ranges then mechanical accuracy? 

How does the hit probability of the 5.56 Neckless stack up to the regular 5.56 M855/SS109 at 300 and 600m? 

EmericD

From: EmericD

22-Aug

gatnerd said:

The bullet jump being comparable to CT/LSAT ammo is interesting. I wonder if that means they are also comparably ~3moa?  I'm surprised the differences between 1-4moa had such minimal effect on hit probability. I guess drop, wind drift, and shooters error are more of a factor at those ranges then mechanical accuracy?  How does the hit probability of the 5.56 Neckless stack up to the regular 5.56 M855/SS109 at 300 and 600m? 

As the CT round is using a movable chamber, you have also to take into account the possible lack of alignment between the chamber and the barrel (that's a critical part of revolver's accuracy).

So, here is the hit probability of an M4 firing the M855A1 at 300 m +/- 30 m, with a +/-3 mph wind, against an IPSC target.

1 MoA system (shooter + rifle) => 77.5% ***** 2 MoA => 75.8% ***** 3 MoA => 73.1% **** 4 MoA => 69.5%

Same system at 600 m +/-60 m.

1 MoA system => 6.2% ***** 2 MoA => 6.1% ***** 3 MoA => 6.1% **** 4 MoA => 5.9%

For a HK416 firing an hypothetical BO F6 "D" at 300 m +/- 30 m, with a +/-3 mph wind, against an IPSC target.

1 MoA system => 83.4% ***** 2 MoA => 81.7% ***** 3 MoA => 78.9% **** 4 MoA => 75.0%

Same system at 600 m +/-60 m.

1 MoA system => 12.6% ***** 2 MoA => 12.3% ***** 3 MoA => 11.8% **** 4 MoA => 11.2%

smg762

From: smg762

22-Aug

If one had a hot round could you keep the barrel cooler with 3 rotating cjambers. Or would it o ly keep the chamber cool.

And could this approach work with normal ammo or only CT. how does a rebolver cannon chamber a normal round if it has 6 chambers

gatnerd

From: gatnerd

22-Aug

EmericD said:

So, here is the hit probability of an M4 firing...

Those are quite promising - effectively a 2x increase in hit probability at 600m even if MOA accuracy is reduced. Also while delivering 9x19 energy levels out to 600m. 

How does hit probability of the Neckless compare to the 77gr SMK? Based on this test of 3x 77gr loads from a 14.5", lets say an avg velocity of 2596fps, using the G7 .190.

https://www.ar15.com/media/mediaFiles/23126/SD-Ammo-233016.JPG

I ask as adopting a FMJ version of the 77gr SMK would seem an "off the shelf" method of improving hit probability / energy retention over SS109 (albeit from my glance at a ballistics chart, delivering 100ft/lbs less energy then the 64gr Neckless at 600m.) 

QuintusO

From: QuintusO

22-Aug

EmericD said:

I still don't think that the "counter performance" of the 70 gr VKO was linked to the bullet stability, because after dealing with the launch AoA, the bullets flew well up to 2500 m. But maybe you want to point out that it could be linked with bullet angle of repose not being ~0°, and shorter twist could (sometimes) mitigate this problem (or not).

Correct, it would have been more accurate for me to say a "stabilization" issue, i.e. twist rate not tight enough. I agree that the bullet was gyroscopically stable after it settled down.

Farmplinker

From: Farmplinker

22-Aug

A lot less accuracy is expected of autocannon; minute of vehicle instead of minute of man.

Also, gas escapes from the cylinder gap make firing revolver weapons from the shoulder either unpleasant, with reduced accuracy, or both.

stancrist

From: stancrist

22-Aug

gatnerd said:

How does hit probability of the Neckless compare to the 77gr SMK?

I ask as adopting a FMJ version of the 77gr SMK would seem an "off the shelf" method of improving hit probability / energy retention over SS109...

1.  Since a FMJ version of the 77gr SMK does not exist, it would have to be developed.  By definition, it is not an "off the shelf" option.

2.  Since the 77gr SMK has a  lead core, and a military FMJ would need to be a lead free bullet, weight would be much less than 77gr.

gatnerd

From: gatnerd

22-Aug

stancrist said:

1.  Since a FMJ version of the 77gr SMK does not exist, it would have to be developed.  By definition, it is not an "off the shelf" option. 2.  Since the 77gr SMK has a  lead core, and a military FMJ would need to be a lead free bullet, weight would be much less than 77gr.

Yes, technically not 'off the shelf' but certainly a 'simple to shelf' development - basically just ask Sierra to close the tip off the SMK. Or a pretty simple project for any of the EU ammo makers that currently make 5.56 bullets to produce a 77gr FMJ in the shape of the SMK. Basically 'off the shelf' in that it requires far less R&D/change then going to a neckless polymer case using cold formed copper VLD's. 

In terms of needing to be lead free, that doesn't seem to be the case for Europe? M855/SS109 is their standard ball (only the swedes as far as I know use the lead free steel core) and all of the various armies that I'm aware of are using lead core 7.62 M80 ball or its equivalent. 

stancrist

From: stancrist

22-Aug

gatnerd said:

Yes, technically not 'off the shelf' but certainly a 'simple to shelf' development - basically just ask Sierra to close the tip off the SMK.

No.  It is not that simple.  The SMK is made with a "reverse drawn" jacket.

FMJ bullets are not made with the "reverse draw" method of construction.

gatnerd said:

In terms of needing to be lead free, that doesn't seem to be the case for Europe? M855/SS109 is their standard ball (only the swedes as far as I know use the lead free steel core)...

A few years ago the UK adopted steel-core L31A1 Enhanced Performance Ball.  New Ammo for British Troops: UK Develops More Effective 5.56mm and 7.62mm Ammunition -The Firearm Blog

As for European countries that choose to stick with lead core, they would probably want to adjust jacket thickness to prevent fragmentation.

In every case, we are talking about a completely new bullet that would have to go through the full design, development, and testing process.

nincomp

From: nincomp

22-Aug

Sierra Bullets now makes at least one "closed tip" HPBT match bullet, the 169grain 308.  I don't know if this would truly be considered sufficiently "closed" by the powers-that-be, though.  Sierra seems to make the distinction between this "closed" bullet tip and its previous "pointed meplat" offerings, but I don't know the details.   According the Sierra:

"This bullet was designed with one thing in mind, and that was to shoot 1000 yards in a 308 Winchester. To accomplish that, Sierra added length to the boattail and engineered a forgiving tangent ogive with a closed nose. Doing this gave it a .527 BC which keeps it supersonic past 1000 yards in a 308 chamber. This bullet is basically a redesign of the legendary 168MK which Sierra will continue to manufacture."

 

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