5.45 vs 5.56 vs 6.5 vs 6.8 vs 300 B:O vs ???

You cant beat 7.62x39 for under 300m. Good penetration, hits hard enough, good out of shorter barrel and designed to be super reliable.
The 6.8 intrigues me since it's pretty much a necked down 7.62x39 so it has better velocity and and range because of better bc.
 
Wasn't this discussion at the heart of the scar program's requirement for multi calibre ability. The goal being to have a single platform to adapt to different environments, thus different tactics.
 
saskcop said:
7.62x39. Decent power. Cartridge tapered design promotes reliability. Very efficient - even from short barrels. Inexpensive. Readily available. .30 caliber! Out penetrates most others in this category.
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As I understand it, the problem with switching to 7.62x39 is that it necessitates switching out all the magazines, and I think I heard that you run into excessive bolt wear with the AR platform as well.

Due to that, 300Blk(7.62x31) has the primary draw of having a very similar cartridge profile to 5.56x45, which lets it feed reliably from the same magazines with no loss of capacity or need to replace components.


My armchair opinion is 300Blk for close range, and 7.62x51 for intermediate and .50 or .338 for long range. However 5.56x45, with appropriate projectile choice, can perform adequately at most ranges it is needed at.
 
Blissified said:
Whats the best intermediate cartridge?
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The best for what? This is like asking what is the best vehicle? Depends on what you want to do with it and what kind of performance you expect.


saskcop said:
7.62x39. Decent power. Cartridge tapered design promotes reliability. Very efficient - even from short barrels. Inexpensive. Readily available. .30 caliber! Out penetrates most others in this category.
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Not if you are planning to run it through an AR its not. 762x39 breaks AR bolts with abandon. It also takes a less common bullet size so there is much less bullet availability in the marketplace.

In an AR, 300 BLK is a better choice with similar ballistics.
 
5.45 vs 5.56 vs 6.5 vs 6.8 vs 300 B:O


I'm inclined to support the 6.5 Grendel. Not that it matters though since the cost of switching to a new calibre would be so large. Even if you stick with the M16 FOW you still need (at the very least) new barrels, new bolts, new mags. What about all those ACOGs that are calibrated for 5.56?

If we look strictly at ballistic performance I think that the 6.5G is the best all-around general purpose cartridge out of the bunch. Why? In general it offers more energy than the 5.45 and 5.56, it offers better long range performance than the 6.8SPC while providing similar levels of energy on target. As for the .300 Blackout, personally, and this is arguable of course, but I think it's a niche cartridge that isn't really well suited to being a general purpose military cartridge. Why? Assuming a ~120-130gr loading it will have more drop and lose energy faster than most of these cartridges making it less suitable as a cartridge that can handle situations out to 500 or 600 metres.

I think the chart at the link below provides a good summary of the situation.

http://ingunowners.com/forums/long-guns/323595-anyone-own-ar-chambered-6-8-spc-opinions.html
ballistics.jpg


Here is a link to some gel testing of the 6.5 Grendel along with some other calibres
http://www.youtube.com/watch?v=BROdbEm5wqA

Some may say that the 6.5G with its steep shoulder would make it unreliable, unsuitable for belt-feed, etc. but I believe that thinking may be flawed. If you look at the 7.5x55 Swiss cartridge, for example, and its shoulder angle to that of the 6.5G the are fairly similar. The Swiss feed 7.5x55 through their MG51 so I would argue that it is possible to make the 6.5G work in the LMG role.

http://upload.wikimedia.org/wikipedia/commons/5/59/7.5_x_55_Swiss.jpg [7.5x55mm dimensions]
http://www.saami.org/PubResources/CC_Drawings/Rifle/6_5 Grendel.pdf [6.5G dimensions]

If trying to use the M16 FOW I can forsee one issue and that is case rim diameter. The 5.56 has a case rim diameter of 9.60mm whereas the 6.5G has a rim diameter of 11.20mm. From what I understand, and I could be wrong, is that opening up the bolt face to accept the larger cartridge can weaken the locking lugs to the point where breakage becomes more of a problem in military weapons that will see much higher round counts than civilian sporting or precision rifles. I do believe the 6.8SPC has a smaller case rim diameter so that is a point in favour of the 6.8 when adapting it to the M16FOW. I'm not sure if it's possible to address the issue of breakage with a bolt redesign so maybe someone could speak to that. In order to move to a cartridge with a large case rim diameter I imagine that the best solution is to use it in a system that has been designed around said cartridge (with lugs big enough to resist breakage!) which opens up another entirely different can of worms in replacing the M16FOW - which is beyond the scope of this discussion IMO.

The 6.5G isn't going to be the best cartridge for every situation but I think it offers the most flexibility in MOST situations compared to all the others.

Edit:
http://www.quarry.nildram.co.uk/The Next Generation.htm [/thread]
 
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In my humble opinion spending mental energy debating calibre choices for small arms is a waste, as far as the big picture goes.
All the calibres mentioned have their pro's and con's, but none of them mean anything when wars are being fought with both hands tied behind our backs (absurdly restrictive ROEs) against an enemy that has no such constraints, and with an irrationally sensitive public that demands soldiers lives be sacrificed so that even one "civilian" life not be put in harm's way.

# of Americans killed by Japanese insurgents since they dropped 2 nukes: 0
# of Americans killed by Afghanis insurgents since NATO appeased, negotiated and co-operated with scumbags: 2,000+

NATO can adopt the most state of the art Plasma Rifles in the 40 Watt range (Google for reference) and it wouldn't make a lick of a difference if they are using them to proper effect.
 
Benito said:
In my humble opinion spending mental energy debating calibre choices for small arms is a waste, as far as the big picture goes.
All the calibres mentioned have their pro's and con's, but none of them mean anything when wars are being fought with both hands tied behind our backs (absurdly restrictive ROEs) against an enemy that has no such constraints, and with an irrationally sensitive public that demands soldiers lives be sacrificed so that even one "civilian" life not be put in harm's way.

# of Americans killed by Japanese insurgents since they dropped 2 nukes: 0
# of Americans killed by Afghanis insurgents since NATO appeased, negotiated and co-operated with scumbags: 2,000+

NATO can adopt the most state of the art Plasma Rifles in the 40 Watt range (Google for reference) and it wouldn't make a lick of a difference if they are using them to proper effect.
Click to expand...

perhaps just avoid dirty wars all together?
 
Benito said:
In my humble opinion spending mental energy debating calibre choices for small arms is a waste, as far as the big picture goes.
All the calibres mentioned have their pro's and con's, but none of them mean anything when wars are being fought with both hands tied behind our backs (absurdly restrictive ROEs) against an enemy that has no such constraints, and with an irrationally sensitive public that demands soldiers lives be sacrificed so that even one "civilian" life not be put in harm's way.

# of Americans killed by Japanese insurgents since they dropped 2 nukes: 0
# of Americans killed by Afghanis insurgents since NATO appeased, negotiated and co-operated with scumbags: 2,000+

NATO can adopt the most state of the art Plasma Rifles in the 40 Watt range (Google for reference) and it wouldn't make a lick of a difference if they are using them to proper effect.
Click to expand...

Fighting a uniformed army and fighting an insurgency are two very different things. To compare them is just absurd.
 
Benito said:
In my humble opinion spending mental energy debating calibre choices for small arms is a waste, as far as the big picture goes.
All the calibres mentioned have their pro's and con's, but none of them mean anything when wars are being fought with both hands tied behind our backs (absurdly restrictive ROEs) against an enemy that has no such constraints, and with an irrationally sensitive public that demands soldiers lives be sacrificed so that even one "civilian" life not be put in harm's way.

# of Americans killed by Japanese insurgents since they dropped 2 nukes: 0
# of Americans killed by Afghanis insurgents since NATO appeased, negotiated and co-operated with scumbags: 2,000+

NATO can adopt the most state of the art Plasma Rifles in the 40 Watt range (Google for reference) and it wouldn't make a lick of a difference if they are using them to proper effect.
Click to expand...

Until you figure out the difference between fighting a War and an Insurgency you will be wrong. Kind of like when trying to fight an insurgency by fighting a war you will always lose.
 
Benito said:
In my humble opinion spending mental energy debating calibre choices for small arms is a waste, as far as the big picture goes.
All the calibres mentioned have their pro's and con's, but none of them mean anything when wars are being fought with both hands tied behind our backs (absurdly restrictive ROEs)

NATO can adopt the most state of the art Plasma Rifles in the 40 Watt range (Google for reference) and it wouldn't make a lick of a difference if they are using them to proper effect.
Click to expand...

No need to google a reference, I never forget a Classic Schwarzenegger line. Arnie always know's his weapons like the gun-store owner states in this Terminator scene.
 
Given the OP's original parameters,
I would be pushing for the development of caseless ammunition and compatible platform. The only issue would be development and testing time.
If they needed it done sooner with a conventional cartridge, I would choose the Murray 7x46mm uiac.
 
Gunnerlove said:
The current first world crop of 5.56x45 rifles shoot way better than 95% of users.

The other 5% could use improved optics and match ammo to reach out beyond 500m.
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This is true. I used to make solid hits on static X-rays at 500m with a 10.3"bbl L119 and good hits out to 300m on a dynamic X-ray with same. There are guys on here who have witnessed my making those types of shots on 20"×20" gongs at those distances. Not just one round, but dozens in a row.

-S.

P.S. I was not as accurate as my service weapon was to boot. The rifle was capable of 1.5-2 MOA. In my hands it was 2.5 MOA/MOT when pucker factor was considered.
 
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cheeseburgereatin said:
perhaps just avoid dirty wars all together?
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War, in general, is dirty. Do you mean we should avoid all war, period?
Are you of the opinion that we should have not fought in WWII because it was "dirty"? After all, we did fire bomb many a German city, and killed far more civilians in a typical day than we have killed cumulatively in every war since then.

Stephen1546 said:
Fighting a uniformed army and fighting an insurgency are two very different things. To compare them is just absurd.
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You claim that it's absurd to compare Islamic terrorists with German Nazi's or Japanese Fascists, yet overlook all the similarities that these groups share.
Totalitarian and supremacist ideology: Check.
Desire to destroy us: Check.
Disregard outdated conventions that we continue to adhere to: Check.
Use every weapon and tactic available to them: Check.
Fight to the death: Check.

This obsession with whether an opponent wears matching uniforms and has a formal rank structure is what's absurd.
The principles of combat, human psychology, tactics and strategy do not change depending on whether your uniforms all look alike.
Crushing, demoralizing and humiliating the enemy works, no matter which way you slice it.

Gunnerlove said:
Until you figure out the difference between fighting a War and an Insurgency you will be wrong. Kind of like when trying to fight an insurgency by fighting a war you will always lose.
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Until you figure out that you are drawing a false distinction, we will continue to lose soldiers' lives in a futile attempt at fighting a war a "perfect" war.
The reason we have been losing the war for the past 12 years is that we have been trying to approach it like it's some special case.

"Winning" hearts and minds, rebuilding infrastructure (that the enemy will use against us), bending over backwards to avoid "civilian" casualties (the quotation marks are there because many of those supposed civilians are actually combatants), imposing suicidal ROEs on our troops and appeasing the enemy are exactly what has been the problem.

An insurgency is still a subset of war. It may not be state vs. state, but the underlying principles are still the same.
 
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