The Firing Line Forums

Go Back   The Firing Line Forums > The Hide > The Art of the Rifle: Semi-automatics

Reply
 
Thread Tools Search this Thread
Old October 14, 2018, 03:48 PM   #101
Bartholomew Roberts
Senior Member
 
Join Date: June 12, 2000
Location: Texas and Oklahoma area
Posts: 7,605
Well, I think you nailed it rickyrick. SOCOM, Army, Marines, Navy... they’ve all looked at 6.8SPC and decided the juice wasn’t worth the squeeze. They’ve done about everything they can given the restraints of the AR15 action and magazine well.

There appears to be a strong desire to penetrate peer competitor body armor at 600m. I’m kind of skeptical that giving troops the equivalent of a .270 Magnum in a lightweight package with a short barrel is going to result in good things. Especially if you have a weapon and ammo that is too expensive to train with.

The Army stating this weapon is too expensive for them to arm everyone with it gives me pause.
Bartholomew Roberts is offline  
Old October 14, 2018, 05:27 PM   #102
davidsog
Senior Member
 
Join Date: January 13, 2018
Posts: 325
Just let em know they ask you!
davidsog is offline  
Old October 14, 2018, 09:50 PM   #103
marine6680
Senior Member
 
Join Date: July 24, 2012
Location: Parker, CO
Posts: 4,573
In the Recoil article linked above...

They show a 6.5 caliber using the new bimetal case... That interests me more than a 6.8 does.

It appears to be similar in length to 5.56, but it may be a bit longer. The case looks like it has a bit more internal volume as well. Looks like what I have been talking about.
marine6680 is offline  
Old October 14, 2018, 11:32 PM   #104
stagpanther
Senior Member
 
Join Date: March 2, 2014
Posts: 5,173
Quote:
It appears to be similar in length to 5.56, but it may be a bit longer. The case looks like it has a bit more internal volume as well. Looks like what I have been talking about.
Looks more like 2.8" xx308 to me--as do the weapons/magazine pics. The bimetal case design is what fascinates me--in the bigger scheme of things I can't see how a .0000x ounce per cartridge saving adding up to anything significant to the soldier lugging the ammo can around is going to notice. Case head is often what flows/fails when the pressures ramp up, so I'm thinking we might (?) be looking at a cartridge design intended to run at significantly higher pressures.
__________________
I screw things up--so you don't have to.
I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!
stagpanther is offline  
Old Yesterday, 03:04 AM   #105
marine6680
Senior Member
 
Join Date: July 24, 2012
Location: Parker, CO
Posts: 4,573
You think? It looks smaller than a 308 based case to me. I could just be seeing it wrong on my phone screen.

20% weight difference is not insignificant, if an ammo load weighed 5lb, it would be 4lb at 20% less weight.

Polymer hybrid designs are starting to be viable as well. I think they save a little more. My only concern would be the case holding up when loaded for a long time. Mag fed shotguns have the issue of deformed hulls when left loaded for a while. But shotgun hulls are fairly weak though.


When it comes to making good ordinance and weapon decisions... The US military has a spotty record at best.

The M14 was a flop of a rifle, that came about because the ones in charge didn't want to listen to the ones that did the studies and research, nor the Brits who had picked up on the idea of intermediate calibers very quickly after WWII.

The higher ups who hated the idea of the M16 deliberately worked to sabotage the rifle, including messing with the design, not training on proper care and cleaning, and knowingly sending out known bad ammo to the field... Things they knew would cause casualties.

You want a good rifle and ammo combination... Ask those outside the military. So long as they don't have any vested interest in the weapons and ammo the military may adopt... And they have a good grasp of ballistics and bullet design.


M855a1 works well from the reports coming in about it... But it is hard on the rifles. So a change in caliber does make sense. But you have to take a realistic look at the needs and realities. I still don't think a single caliber will cut it... You need the general issue to be very effective inside 300yds, but still useful out to 500yds give or take. For effective use past 500yds, you would need something else. And yet one more for use in an SBR, that is effective inside 100-150yds. I just don't think a signle round can do all those well. Maybe you could have a single caliber but different variations, and it would work.


But as was said... No matter what you choose, the military is limited on bullet design. So civilian ammo will still likely be better.
marine6680 is offline  
Old Yesterday, 06:11 AM   #106
stagpanther
Senior Member
 
Join Date: March 2, 2014
Posts: 5,173
Take a look at the article linking to Sig's submissions. I think it's easy to see that's not a 2.26 cartridge. Take a closer look at the weapons--it's also easy to see the magazine is also not a short 2.3 +/-.

What's also interesting to see is that the carbine weapons are buffer-less designs by virtue of the lack of buffer tubes and folding stocks. Pretty obvious it's a gas-piston system with some sort of carrier system for absorbing recoil all within the upper receiver--might even be a side-charger. I'm going to guess there's some kind of facility for quick and easy barrel swap-out as well.

Looks like they also are going with some kind of special coating on the projectile--I'm guessing they found a coating that reduces friction and increases velocity while reducing bore fouling. Or maybe it's just a coating to hide the new super-secret frickin-sharks-with-lasers projectile technology?
__________________
I screw things up--so you don't have to.
I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!

Last edited by stagpanther; Yesterday at 06:19 AM.
stagpanther is offline  
Old Yesterday, 06:32 AM   #107
stagpanther
Senior Member
 
Join Date: March 2, 2014
Posts: 5,173
There's not only how well the system works--but how well it fails. I see a potential high pressure multiple-part cartridge design and my first reaction is "rut-rooh." Tiny little headspace or jam issues have a nasty way of potentially rapidly increasing pressure. Having blown up a couple of rifles myself--I'd be interested in what happens in a failure mode. Having troops in the field testing portable IED's isn't very fair way to test that.
__________________
I screw things up--so you don't have to.
I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!

Last edited by stagpanther; Yesterday at 06:37 AM.
stagpanther is offline  
Old Yesterday, 11:39 AM   #108
Bartholomew Roberts
Senior Member
 
Join Date: June 12, 2000
Location: Texas and Oklahoma area
Posts: 7,605
Speaking of pressure, even if they are using a low-friction coating on the projectile, throat erosion on that has got to be tremendous. Some type of new surface treatment that is extremely resistant to heat checking?
Bartholomew Roberts is offline  
Old Yesterday, 04:43 PM   #109
Jim Watson
Senior Member
 
Join Date: October 25, 2001
Location: Alabama
Posts: 15,049
The USMC tried real Teflon coating on bullets.
Some promising early observations could not be reproduced, so they gave up on it.
Jim Watson is online now  
Old Yesterday, 04:57 PM   #110
marine6680
Senior Member
 
Join Date: July 24, 2012
Location: Parker, CO
Posts: 4,573
I was looking at the recoil article that Bart linked to.

It had a cartridge that was labeled using a lable maker, as 6.5 on it's side. I do not recall seeing that in the original links. With those being obviously larger than typical 5.56 dimensions.


Failure can be factored in... A case rupture is bad all around, exactly where it fails is less of a concern in the end.

Lots of testing will be required to know if the new type of case works long term.

Barrel wear can be controlled with good design of the caliber. The ratio between the case diameter and neck diameter plays a role, as well as other factors.
marine6680 is offline  
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 09:58 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
This site and contents, including all posts, Copyright © 1998-2018 S.W.A.T. Magazine
Copyright Complaints: Please direct DMCA Takedown Notices to the registered agent: thefiringline.com
Contact Us
Page generated in 0.10261 seconds with 9 queries