Image result for cartoons give me a break

Hope you all had a great week. Friday is upon us and we all look forward to a well deserved weekend.

Who’s tired of all the partisan B.S. coming at you from the Democratic Congress and a main stream media functioning as a public relations firm for the Democrats? If I hear one more thing about V.P. Joe Biden’s unauthorized kissing and shoulder rubbing, Jussie Smollett and D.A. Foxx, Alexandria Ocasio-Cortez and the Inquisition of Donald J. Trump, POTUS, by a Congress that insists there was collusion with Russia and don’t confuse them with facts, I’m going to puke! However, instead of regurgitating or seeking the services of some jackass who studied psychology so that he or she could understand themselves, I’ll get a shoot the shit going.

So here we go…

Have you guys been keeping up with the U.S. Army’s initiative to develop / acquire the Next Generation Squad Automatic Rifle (NGSAR)? As I understand it, the Army is looking to replace the M249 SAW and M4/M4A1 carbines with new weapons chambered in the Army’s newly developed 6.8mm round. The first thing that came to mind was Remington’s 6.8 SPC (special purpose cartridge) but that was the wrong answer. The Army has actually developed its own 6.8 mm bullet. Why?

Behind the U.S. Army’s desire to embrace the new 6.8 mm round are two performance parameters, superior terminal ballistics and lethality. Let’s take a more granular look at lethality.

The 5.56 x 45 NATO round was developed around the M16 which has a 20” barrel. It relies on a 3,000+ fps muzzle velocity to produce the bullet fragmentation needed for effective lethality. For good reason, the U.S. Army transitioned from the M16 rifle to the M4/M4A1 carbine, so barrel length went from 20” to the 14.5” of the M4/M4A1. There’s a fairly reliable rule of thumb that says for every inch of barrel length reduction, you give up approximately 50 fps of muzzle velocity. So, we went from approximately 3,150 fps 62 grain projectile to approximately 2,875 fps. or well bellow the velocity needed to ensure proper bullet fragmentation. The solution was to design a bullet with adequate penetration and constructed of a material and geometry that allows proper fragmentation at the lower muzzle velocities of the M4/M4A1. It resulted in the introduction of the Enhanced M855 designated as the M855A1.

Testing The Army’s M855A1 Standard Ball CartridgeImage result for 6.8SPC

M855A1                                                   6.8 SPC

Apparently, the M855A1, which has now been in use long enough to develop extensive performance data, is inadequate. The Army is concerned about the M855A1 rounds’ ability to defeat the new Chinese and Russian body armor. An interesting point because as it stands today, properly manufactured Level IV plates are capable of defeating 5.56 x 45, 7.62 x 39, 7.62 x 51 and several other rifle or carbine cartridges; armor piercing projectiles excluded. So, what does the Army’s 6.8mm got going that makes it effective against the Chinese and Russian armor?

The Army has not made public its 6.8 specifications but it’s safe to assume that you’ll see a 115 grain – 125 grain projectile at a muzzle velocity of 2,400 fps – 2,600 fps. I can’t imagine something like that defeating a Level IV plate. So, is it an APC projectile or does it have a specific bullet geometry or some form of a compound that melts through the plate a la antitank ordnance.

So what’s the benefit given what we know today. The 6.8mm round has a .4 or slightly greater ballistic coefficient at 2,400+ fps. As such, it has a flatter trajectory and better performance at longer ranges including kinetic energy ( the formula for kinetic energy is KE= 1/2 m.v2 so increasing the bullet weight increase the kinetic energy given a constant velocity). So, other than sniper or designated marksman roles are we expecting our soldiers to engage point targets out to 600 meters with their carbines? Not likely, what you’ll generally see at ranges beyond 300 meters is area fire for suppression.

Assuming that lethality and accuracy are improved with the 6.8 cartridge, what’s the cost? What immediately comes to mind is its weight, the 6.8 bullet weighs approximately 120 grains whereas the 5.56 x 45, M855A1, is 62 grains, so it’s twice as heavy and that’s just the bullet. The cartridge weight for M855A1 is about 12 grams and the 6.8 SPC is slightly heavier coming in at approximately 17.4 grams or 5+ grams heavier per round. The only way to mitigate the negative effects of weight is to use a polymer case. And that, in my opinion, is fraught with danger.

Polymers at the molecular level are single chain materials, which means that a break in the chain leads to the deterioration of the polymer. Bacteria, for example, will metabolize just about anything you can think of or they can be engineered to metabolize specific compounds.

One strain of bacteria that is particularly problematic for polymers is the 201-F6 strain. When it acts on plastics, it uses two enzymes to break down and eat plastics, think of it as feeding on plastic. The two enzymes are PETase and MHETase . Now, this is just one bacterial strain. 201-F6 can also be cultivated and engineered. Here’s what that means, if released on weapon caches or storehouses it could, over time, the estimate is about 6 to 8 weeks at 30°C, break down the cartridge polymer case, creating some potentially serious problems. Polymers are great but you need to be cautious and understand the risks and I’m not sure I like polymer cases on my ammunition.

If you have a handle on the Army’s 6.8 initiative please chime in.

Remember, as with all shoot the shits, participants don’t need to know anything about the subject being discussed, you can make any unsupported statement, you can use uncensored profanity, insult anyone you wish or change the subject. Have a great weekend, be safe and spend some quality time with your buds and family.

This entry was posted in Shoot-the-shit and tagged , . Bookmark the permalink.