gatnerd

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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NGSW Phase 2 Consolidation and info   Small Arms <20mm

Started 30/8/19 by gatnerd; 520447 views.
Red7272

From: Red7272

6/9/19

gatnerd said...

Emeric, do you need to sue?

This looks very similar to something he showed us years ago. Polymer case with a thickened shoulder that was glued to the projectile. It would make long ogive version of existing round possible.

In reply toRe: msg 59
gatnerd

From: gatnerd

7/9/19

It also appears similar to this 25x145mm exerimetal polymer/neckless case:

http://www.quarryhs.co.uk/tankammo5.html

In reply toRe: msg 60
Wessels3

From: Wessels3

7/9/19

Just for interest sake, the recoil energy of a few relevant rounds:

The MARS/Cobalt 6.8 cartridge: 14.0 kg.m/s. 140 grains at 3200 ft/sec., using an estimated 56 grains of propellant: 15 kg.m/s. 

30-06:             12.3 kg.m/s.  (150gr at 2800 ft/sec + 50gr of propellant)

7.62 NATO:      11.6 kg.m/s. (150gr @ 2700 ft/sec + 45gr propellant)

The 6.8 cartridge has about 14% more recoil than the 30-06. We know that the second model FG42 was "reasonably" controllable on full-auto, with a cartridge similar in power to the 30-06. It did have an efficient muzzle brake though, and a well designed stock.

gatnerd

From: gatnerd

7/9/19

"Just for interest sake, the recoil energy of a few relevant rounds:

The MARS/Cobalt 6.8 cartridge: 14.0 kg.m/s. 140 grains at 3200 ft/sec., using an estimated 56 grains of propellant: 15 kg.m/s. 

30-06:             12.3 kg.m/s.  (150gr at 2800 ft/sec + 50gr of propellant)

7.62 NATO:      11.6 kg.m/s. (150gr @ 2700 ft/sec + 45gr propellant)

The 6.8 cartridge has about 14% more recoil than the 30-06. We know that the second model FG42 was "reasonably" controllable on full-auto, with a cartridge similar in power to the 30-06. It did have an efficient muzzle brake though, and a well designed stock."

Good info.

In terms of recoil, its worth noting that suppressors reduce recoil by ~25-45% depending on suppressor and cartridge.

One .308 test:

With a 25% recoil reduction, it would be 10.5kg/ms

33% = 9.38 m/s

Then there's also the effect of hanging a 1lb metal tube on the muzzle, which should certainly help to reduce muzzle climb. 

  • Edited 07 September 2019 8:58  by  gatnerd
poliorcetes

From: poliorcetes

7/9/19

How a suppressor can reduce recoil by 45%?

 

I mean, blowed gas are responsible of a minor part of recoil. A suppressor eliminates reaction forces caused by gas, but it is not used as a counter-recoil force against recoil direction like a muzzle brake does diverting gas at high speed

gatnerd

From: gatnerd

7/9/19

"I mean, blowed gas are responsible of a minor part of recoil. A suppressor eliminates reaction forces caused by gas, but it is not used as a counter-recoil force against recoil direction like a muzzle brake does diverting gas at high speed."

Gas is responsible for like 50% of the recoil of a rifle.

https://www.thetruthaboutguns.com/ar-15-muzzle-brake-shootout-3/

Muzzle devices can have a profound effect on recoil. In 5.56, the dead air sandman suppressor reduces recoil by 46%. The best muzzle break reduces it by 78%, but with intollerable levels of blast. 

The Surefire Warcomp, the ideal military compensator/flash hider, cuts recoil by 35%.

 

EmericD

From: EmericD

7/9/19

poliorcetes said...

I mean, blowed gas are responsible of a minor part of recoil. A suppressor eliminates reaction forces caused by gas, but it is not used as a counter-recoil force against recoil direction like a muzzle brake does diverting gas at high speed

For handguns, yes, but for rifles powder load is a substantial part of the recoil.

For example, let's take the 7.62 mm NATO M80 (9.5 g bullet at 850 m/s, and a 2.9 g powder load).

The impulse produced by the bullet alone is 9.5*.85 = 8.1 N.s, when the total impulse as measured on a ballistic pendulum is 11.6 N.s, so the gases are producing ~30% of the total recoil, that is 2.9 g of powder with an speed of ~1200 m/s.

The conical muzzle brake on the Lee-Enfield "jungle carbine", while very effective to dissipate the muzzle flash, acted like a rocket-engine nozzle and increased the recoil impulse by 10%.

Wessels3

From: Wessels3

7/9/19

What it basically comes down to is that the recoil of a hot 6.8mm round will not be a problem. The weapon system will not be very light, with lights, sights and lasers stuck on it, as well as a suppressor. The weight helps to reduce recoil and then there is the suppressor, as you showed, which also reduces recoil. And, of course, the suppressor reduces the other issue with hot rounds, i.e. muzzle blast and flash.

EmericD

From: EmericD

7/9/19

Red7272 said...

Emeric, do you need to sue?

This looks very similar to something he showed us years ago. Polymer case with a thickened shoulder that was glued to the projectile. It would make long ogive version of existing round possible.

Yes, it' very similar to (but probably better than) the 7,62x43 "neckless" I made years ago with a shortened aluminium/plastic case of blank ammo.

The involvement of Beretta is interesting, a few month ago their head of product development told me they were working on a different rifle than the ARX series, so maybe there's a link to investigate.

In reply toRe: msg 67
gatnerd

From: gatnerd

8/9/19

A little bit more on SIG:

https://www.recoilweb.com/sig-sauers-secret-sauce-to-winning-146832.html

Best photos so far of their cartridge and case design:

"SIG opted for a bi-metallic, multi-piece case instead of a telescoping polymer case. During testing, SIG learned that it’s difficult for polymer rounds to keep high pressures. As of December 2018, SIG has demonstrated at two separate locations for the U.S. Army the 6.8mm Hybrid ammo shot from a 16-inch barrel at 3,000 feet per second.

One of the many benefits of SIG’s Hybrid ammo is that it can be used in legacy firearms. For the regular consumer, this translates to access to high-pressure, high-velocity rounds in the future that we can use in the guns we already own. For competitors, Lindsay Bunch, of the Strategic Weapons Group, likens the increased performance of the hybrid ammo to getting 24-inch bolt gun velocity in a 16-inch gas gun."

 

Most interesting is a look into their .338 LWMMG, of which their NGSW LMG is based upon. This gives some hint as to how it works:

"The SIG SAUER Lightweight 338 Machine Gun is their answer to a USSOCOM Request for Information solicitation for a Lightweight Medium Machinegun (LWMMG), which should replace the M240. SIG says this 338 is the big brother to the machine gun that will be submitted for the NGSW-AR solicitation to replace the M249. The machine gun has been developed by an engineer with more than 30 years of experience building machine guns — it’s his specialty. Weighing under 20 pounds, the 338 Norma Magnum machine gun fires a bullet at 2,650 feet per second out of its 24-inch barrel and that projectile is still supersonic at 1,500 yards. And it has a cyclic rate of 500 to 600 shots per minute. We’d expect a magnum caliber to have quite a bit of kick, but the SIG team says the unique recoil design produces less felt-recoil than a 308 Winchester. To put it into perspective, the SIG MCX, chambered in 5.56, puts 2 foot-pounds of energy into your shoulder, while the SIG .338 machine gun delivers 3 to 4 foot-pounds of energy to the shooter’s shoulder, according to SIG engineers."

 

 

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