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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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Useful Firearms Design Features   Small Arms <20mm

Started 12/10/17 by gatnerd; 12055 views.
In reply toRe: msg 67
gatnerd

From: gatnerd

31/10/17

AR/M4 Specific Design Features Part 1 - coming soon

Full Auto Enhancements: One of the chief design goals of the Sturmgewehr/ Assault Rifle concept was to have a weapon with the close quarters firepower and controllability of a submachine gun, with the accuracy and range of a rifle. This was later further emphasized with the development of SCHV ammunition - which was specifically intended to further improve the controllability of Assault Rifles in their fully automatic role.

Sadly, the Assault half of the Assault Rifle concept has been fading away nearly since the inception of the M16 - which was first issued with 20rd magazines, then further neutered with the introduction of the 3-round burst in the M16A2. Subsequent enhancements to the M16 and M4 have all focused on the Rifle side, through the use of superior sights and magnified optics. Doctrine has largely shifted to the almost exclusive use of Semi Auto - effectively relegating the promising SCHV Sturmgewehr into a low powered Battle Rifle.

However in the last few years, the utility of Full Auto has been rediscovered by the Marines - first with their IAR M27 - which is simply a SCHV assault rifle with a bipod, and then subsequent testing they conducted against moving targets, which showed that hit rates averaged 40% in semi auto, but rose to 60% when using bursts of full auto. 

In addition to the improved hit rate full auto can offer, it also offers a possible counter to the proliferation of body armor, especially in CQB/Urban combat. While nothing short of tungsten will defeat hard armor, a controllable full auto weapon offers a higher chance of hitting the soldiers unprotected extremities then single shots - especially against a moving, armored target. 

Therefore, the features in this section will be devoted to ways to improve the full auto controllability and effectiveness of the M4 carbine, and put the Assault back in Assault Rifle. 

Armwest + Surefire reduced rate of fire / "constant recoil" bolt carrier: The first step to improving the full auto effectiveness of the M4 is reducing its rate of fire - which is currently between 850-950rds per minute, and over 1000rpm when suppressed. A reduced rate of fire a) improves controllability b) reduces ammunition consumption and c) improves reliability - especially with drums and quad stack mags - as it gives more time for the magazine to present a fresh cartridge.

James Sullivan - designer of the AR15 and Ultimax, has partnered with Surefire to release his drop in, reduced ROF bolt assembly. The bolt carrier uses a floating weight and redesigned gas key to lengthen the cycle time from 28 Milliseconds to 38 Milliseconds. In Surefire's testing with a 14.5" Midlength FN, rate of fire was reduced from 850rpm to 588rpm, and from over 1000rpm suppressed down to 750rpm suppressed:

https://www.youtube.com/watch?v=L8JWUvt65eo

http://www.defensereview.com/surefire-optimized-bolt-carrier-long-stroke-obc-ls-drop-in-bcg-and-h7s-buffer-system-for-better-weapon-control-reliability-and-durability-best-tactical-ar-15m4m4a1-carbineshort-barreled-rifle/

Closed bolt SA/Open Bolt FA trigger group: The 2nd upgrade developed by Armwest, designed to go along with the reduced ROF bolt carrier, is a trigger group that is designed to fire from a closed bolt in semi auto, and then convert to open bolt mode when firing in full auto. This is primarily to prevent cookoff when the rifle is used in FA. It may? also help with his "constant recoil system." (if anyone can confirm or deny, that would be great.) 

--> Armwest's combination of the new Bolt Carrier and the Open bolt FA trigger creates a weapon with a "constant recoil system almost as good as the Ultimax 100" to the point where the rifle can be fired one handed off the shoulder. 

Video here / comparison between the M4 and Enhanced M4, testing begins at 10:06:

https://www.youtube.com/watch?v=gOUKXIrDE0I

And a video of the Ultimax 2000 - giving an idea of just how effective a constant recoiling weapon can be:

https://www.youtube.com/watch?v=R1zQuWpsYZY

Geissele High Speed Selector / "Gas Pedal.": While the Armwest/Surefire M4 upgrades creates a controllable full auto weapon, the High Speed Selector by Geissele enhances performance by allowing soldiers to have instant access to full auto, without the risk of getting stuck in full auto should a sudden, precision shot be required. This is huge, as one of the chief detriments to previous full auto selectors is that full auto can be extremely limiting - especially in an urban insurgency where precise shots to avoid civilians may be essential. 

It also makes full auto much more effective, because it reduces the throw from 180 degrees to 90, allowing a much faster response time against sudden, rapidly moving targets:

"About a year ago, the United States Marine Corps (USMC) gunner community approached Bill Geissele about a selector switch issue they were having on their guns (M4 Carbines). Basically, they’ve been getting a 40% hit rate in the semi-auto-fire mode on moving targets exposed for 2.2 seconds while moving at 10 mph at a distance of 50-150 yards, and it was taking too long to flip the happy switch over to full-auto, where they can get 60% hits, which is a whopping 50% improvement."

"So, Geissele developed a spring-loaded 45-degree-throw selector switch (between the semi-auto and full-auto positions) that the shooter can instantly push into full-auto with their thumb, and then right back into semi-auto by releasing the pressure. It comes RIGHT back to sem-auto."

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  • Edited 01 November 2017 1:08  by  gatnerd
In reply toRe: msg 68
gatnerd

From: gatnerd

31/10/17

AR/M4 Specific Design Features - Part 2 (coming soon)

CWRPHILLIPS

From: CWRPHILLIPS

1/11/17

Historically the big production crises have not been changing small arms that were not good enough, it has been making enough small arms when a war starts. Modularity sounds great but it adds complexity and hence weight and cost. Also it is limited, so if the required change is large enough you will need a new small arm anyway. So modularity means spending more money in peace time, handicapping your expansion in war time and giving the troops a heavier weapon all for a capability that may be inadequate anyway.

Even if the modularity can be used, how much does it actually save? One of your examples has the introduction of a completely new type of ammunition, requiring massive changes to ammunition production, new barrels, magazines, mag-wells and sights. Would making a completely new rifle, particularly a simple non-modular one, have added that much to the cost? Also how much sooner will your adapted weapon wear out because of all the part worn components?

All the changes that were made to the M16 were made without the design being modular, and most were made by making new weapons, not rebuilding old ones.

The SA80 series upgrades are largely due to Britain's inability to make any new small arms, with training and politics also playing roles. Again it has been done without the weapon being modular.

Also note that we are seeing Germany reject the upgraded G36 option.

gatnerd

From: gatnerd

1/11/17

"Historically the big production crises have not been changing small arms that were not good enough, it has been making enough small arms when a war starts. Modularity sounds great but it adds complexity and hence weight and cost. Also it is limited, so if the required change is large enough you will need a new small arm anyway. So modularity means spending more money in peace time, handicapping your expansion in war time and giving the troops a heavier weapon all for a capability that may be inadequate anyway.

Even if the modularity can be used, how much does it actually save? One of your examples has the introduction of a completely new type of ammunition, requiring massive changes to ammunition production, new barrels, magazines, mag-wells and sights. Would making a completely new rifle, particularly a simple non-modular one, have added that much to the cost? Also how much sooner will your adapted weapon wear out because of all the part worn components?"

Well the first obstacle to overcome is showing that modularity does not really add to weight or cost.

In terms of quick change barrel, it's either a weight neutral, or minimal weight increasing feature. I'm trying to find the weight for the LMT CQB-16 MARS (adopted by NZ), which is the ideal quick change barrel system, but LMT hasn't published any weight specs. I picked it up at SHOT last year and it felt identical to any other AR with a quad rail. 

But we do have the Skeli X11 which is coming out, that features a very similar QCB setup. It weighs 6.8lbs - one of the lightest piston rifles in the world -with a MSRP of $1400. The HK 433 has a QCB, weighs 7.7lbs with 16" barrel - which is less than or equal to the weight of either the G36 or 416. It is also reportedly cheaper then the 416 - despite the QCB feature. 

If we look at the AUG vs F90, at first glance, the deletion of the QCB seems like a big weight savings - the F90 16" weighs 7.15lbs vs 7.8lbs for the 16" AUG flattop - a 10oz weight savings. However on closer examination, the F90's 10oz weight savings comes from 1. replacing the beefy AUG aluminum receiver with polymer receiver+ extensive skeletonization 2. a fluted barrel with a different profile 3. shortening the stock by 5/8" 4. removing the VFG 5. removal of the QCB. So the actual weight savings of just the QCB was likely around 2oz's weight savings or less (it's just a spring loaded latch in the receiver that mates with the gas block.) In terms of cost savings, a) the AUG is a pretty low cost rifle on the open market b) I haven't seen any indication that the F90 will sell for less.

Meanwhile, a modular magwell is just a chunk of polymer, held in with a few pins. It's neither a costly or heavy feature to add - its simply a function of mold tooling, and upfront R&D. The CZ 805 has this feature, and it's a good deal cheaper then the SCAR 16 or ACR. 

In terms of the cost of swapping parts vs buying a new weapon, it is much cheaper to swap the parts. For example, lets take the LMT 308 DMR - currently in service with the UK and NZ - and features a QCB. To convert them to .260 Remington, a new barrel can be purchased for $566 - vs $3,750 for a new rifle. 

Lastly, it seems there is some broader military interest in modular weapons:

 

  • Edited 02 November 2017 0:21  by  gatnerd
Taurevanime

From: Taurevanime

2/11/17

That makes more sense. We have upgraded the AR-15 design as requirements changed, rather than built new weapons. For a future design we should take that into consideration. The main way to do that of course is in construction. Having the gas block more in the middle rather than at the muzzle opens up the possibility for shorter barrels and different devices to be put on the muzzle. This now seems something standard in rifle designs, while the original AR-15 didn't for example.

Sometimes happy accidents occur, like the Minimi was originally intended for 7.62 NATO, but eventually made in 5.56, but the dimensions of the weapon weren't changed for that. So conversion to the larger caliber was easy to perform.

The big problem though is weight and cost. Modularity costs more to build in because it takes time to design and test, but it also adds weight. And as we see with certain procurement, the need for weight to remain low can trump many other requirements.

Dasypus

From: Dasypus

16/11/17

Replace the 7.62x51 with the 7-08 Remington. Only thing that would need changing is the barrel. Magazines, MG belt/links, etc. could stay  the same.

Red7272

From: Red7272

17/11/17

Dasypus said...

Replace the 7.62x51 with the 7-08 Remington. Only thing that would need changing is the barrel. Magazines, MG belt/links, etc. could stay  the same.

And the bodies pile up when someone tries to fire the wrong belt though the wrong barrel. No point to changing the 7.62x51 anyway, it does the job after a fashion and the complexity of the change would be prohibitive. The 5.56x45 is where all the issues are. That is what needs to change, ideally without being limited by existing gun architecture.

Dasypus

From: Dasypus

17/11/17

Why would the bodies 'pile up' Red?

Red7272

From: Red7272

17/11/17

Dasypus said...

Why would the bodies 'pile up' Red?

Well maybe not, but there will be a lot of missing eyes and hands. It's not exactly an idiot proof idea. And as I said, the need is for a better IW not a better LMG round. 

Dasypus

From: Dasypus

17/11/17

There would not be any physical damage at all from firing a 7-08 in a 7.62x51 chamber. I can not chamber a 7.62x51 in a 7-08 chamber as the neck diameter is too large.

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