Someone from the past stole my idea! The 6mm SAW cartridge.

[Podmonkey]

6×45mm SAW - Wikipedia

Modern Historical Intermediate Calibers 010: The 6mm SAW -

General Purpose Combat Cartridge Revisited - Abe's Gun Cave

@Robin this is the cartridge we should adopt,
Should have adopted way back then!

@meketrefe, some bastard traveled from the past and stole my brainchild! And they adopted the awful M885 cartridge instead. How sad.

Anyway, what we have here is a heavy 105gr 6mm projectile launched at around 2,500 fps.
This gives us an 800m effective cartridge that can be effectively used in lightweight infantry carbines at close range as well as in a variety of machineguns at medium to long range.
Yes I would consider 800m long range.
I could see this round efficiently replacing the 5.56 and the 7.62. I could see this round being used in a coax machine gun in an M1 Abrams even. And as I have been saying these ballistics are pretty close to the way ahead of it's time 6mm Lee Navy cartridge.
Personally I'd say get rid of the metal case for brass, or even work on a telescoped polymer case, and use a projectile with the same construction as the M855A1/M80A1 projectiles as the have been shown to be highly effective.
That would give us just about the perfect cartridge.

 

[Podmonkey]

For ultra compact arms for Special Forces and for soldiers that don't need a primary rifle/carbine I would adopt some kind of 'ittle PDW type thing in a cartridge similar to (or adopt outright) the 7.5 FK
For really long range use we are already using the .300 Win Mag while other Nations use .338 Lapua. I would suggest we follow SOCOM's lead, split the difference and adopt the .300 Norma Magnum cartridge.

 

[meketrefe]

It was an idea in the right direction. In reality the neck doesn't have to be that long and
it could be a smaller more compact cartrige for a a 85-100gr bullet.
If one takes the section of a 6.8 or even a .450 bolt face one could make a strong case with
enough capacity to provide a huge leap in the SMB and also give the proper shoulder angle
for military use.
That is why the LBC/grendel in 6mm does better ballistics than the 6.5mm version and
why something like a 6mm wasp with a 25degree shoulder and 42mm case provides a very
easy path based on the 6.8 case.
Even a new case based on the 223 with slightly rebated rim and 44mm would be a great
choice that will yield about a 25 to 30% improvement w/o doing much. That is what the
6x45L and 6TCU do. Simple as cake.

6mm is the way.

 

[Podmonkey]

It was an idea in the right direction. In reality the neck doesn't have to be that long and
it could be a smaller more compact cartrige for a a 85-100gr bullet.
If one takes the section of a 6.8 or even a .450 bolt face one could make a strong case with
enough capacity to provide a huge leap in the SMB and also give the proper shoulder angle
for military use.
That is why the LBC/grendel in 6mm does better ballistics than the 6.5mm version and
why something like a 6mm wasp with a 25degree shoulder and 42mm case provides a very
easy path based on the 6.8 case.
Even a new case based on the 223 with slightly rebated rim and 44mm would be a great
choice that will yield about a 25 to 30% improvement w/o doing much. That is what the
6x45L and 6TCU do. Simple as cake.

6mm is the way.

I guess the dimensional minutiae of what you talk about here goes right over my head. Mostly I am just focusing on the bullet diameter, weight and velocity. You are saying we can accomplish the 6mm SAW's ballistics more efficiently? That's great. Keep in mind we need to keep it effective at long range, we need something that can completely replace the 7.62x51 in all its roles, like that coax machinegun role. M1 Abrams gunners will engage infantry with the .30 cal coax out to 1,000 meters.
In that role the round doesn't have to be especially efficient at that range, just be able to get itself reliably out there, poke some holes, suppress the enemy.

 

[meketrefe]

It will not replace the 7.62x51. It cant. There is a need for both a compact round and a medium round with more
anti-material capabilities. Let me explain...

If one wants to do something in the middle it needs to be a 270 or ideally a 7mm.

The 7mm-08 outperforms the 7.62x51 at everything including long range work.
But then anything like that is going to be too large for the MBR. It will be better than the 308 but not
really the ideal. If we shorten the case to lets say 45mm it will be more compact, very capable but still
too much and anything smaller starts to compromise the performance for middle weight / anti material use.

The problem with 6.5mm and 6mm is not the ballistics or trajectories that are great but the grain
and momentum on the target that is key for military use. If we look at the direction things are going with
lead free ammo and arrowhead perpetrators and what not, the 6mm and 6.5mm will not cut it to cover the 308.

In fact, with CNC solid bullets and modern powders the case for the 308 becomes stronger as it can produce
very similar trajectories to the 6.5mm and deliver more momentum on the target. At the same time can
be made more efficient in shorter barrels and barrels will last longer.

Perhaps the 7mm-08 would be the perfect upgrade from the 308 and the 6mm from the 5.56 but in reality
both will not happen and we need two calibers for the reasons above.

I have done lots of study, calculations, development and test with both my design cats and commercial reloads
with all sort of bullets and came to this conclusion.

SBR: compact 6mm - 85-85gr for infantry use. increases effective range from 500 yards to 800yards and delivers more
punch w/o a huge penalty in size and weight that is key for this role. Firepower is more important than having more
terminal performance.

Mid-weight with more anti-material capabilities. 7mm-08 with a 120-140gr arrowhead penetrator shoots flatter and hits
harder than the 308 moving effective range from 800yards to 1000 yards. Alternatively a 165-170gr bullet will
give snipers a substantial edge over the 308 but still delivering very good momentum on the target.

If the 308 didn't exist it would make sense to do it in 7mm but with that said, the 308 with a modernized cartridge
and solid bullets will also give a huge improvement w/o doing anything else.
So this would make a more reasonable plan to address the improvements of the mid weight by
introducing new bullets (including CNC) and powders that work with the current chambers and weapons systems.

The 6mm SBR will need a new casing thought. a 6mm-6.8spc would be both very simple and a substantial improvement.

Keep in mind that other similar recipes could be produced with .25 and .270 formulas but with the already existing offering
of bullets and baseline components for 6mm and 7mm it is hard to justify introducing more in any other bores
specially odd/exclusive ones like the 25.

Similar results can be archived by a number of bores, casings, designs and bullets that in the end they all yield very similar results
but with those 6mm and 7mm and 30 caliber bores being so plentiful and already researched there is no need.

 

[Podmonkey]

It will not replace the 7.62x51. It cant. There is a need for both a compact round and a medium round with more
anti-material capabilities. Let me explain...

If one wants to do something in the middle it needs to be a 270 or ideally a 7mm.

The 7mm-08 outperforms the 7.62x51 at everything including long range work.
But then anything like that is going to be too large for the MBR. It will be better than the 308 but not
really the ideal. If we shorten the case to lets say 45mm it will be more compact, very capable but still
too much and anything smaller starts to compromise the performance for middle weight / anti material use.

The problem with 6.5mm and 6mm is not the ballistics or trajectories that are great but the grain
and momentum on the target that is key for military use. If we look at the direction things are going with
lead free ammo and arrowhead perpetrators and what not, the 6mm and 6.5mm will not cut it to cover the 308.

In fact, with CNC solid bullets and modern powders the case for the 308 becomes stronger as it can produce
very similar trajectories to the 6.5mm and deliver more momentum on the target. At the same time can
be made more efficient in shorter barrels and barrels will last longer.

Perhaps the 7mm-08 would be the perfect upgrade from the 308 and the 6mm from the 5.56 but in reality
both will not happen and we need two calibers for the reasons above.

I have done lots of study, calculations, development and test with both my design cats and commercial reloads
with all sort of bullets and came to this conclusion.

SBR: compact 6mm - 85-85gr for infantry use. increases effective range from 500 yards to 800yards and delivers more
punch w/o a huge penalty in size and weight that is key for this role. Firepower is more important than having more
terminal performance.

Mid-weight with more anti-material capabilities. 7mm-08 with a 120-140gr arrowhead penetrator shoots flatter and hits
harder than the 308 moving effective range from 800yards to 1000 yards. Alternatively a 165-170gr bullet will
give snipers a substantial edge over the 308 but still delivering very good momentum on the target.

If the 308 didn't exist it would make sense to do it in 7mm but with that said, the 308 with a modernized cartridge
and cnc bullets will also give a huge improvement w/o doing anything else.
So this would make a more reasonable plan to address the improvements of the mid weight by
introducing new bullets and powders that work with the current cambers and weapons systems.

The 6mm SBR will need a new casing thought. a 6mm-6.8spc would be both very simple and a substantial improvement.

Keep in mind that other similar recipes could be produced with .25 and .270 formulas but with the already existing offering
of bullets and baseline components for 6mm and 7mm it is hard to justify introducing more in any other bores
specially odd/exclusive ones like the 25.

Similar results can be archived by a number of bores, casings, designs and bullets that in the end they all yield very similar results
but with those 6mm and 7mm and 30 caliber bores being so plentiful and already researched there is no need.

Eh, I don't really agree. This round was specifically designed for penetration, it exceeds the 7.62x51 in that regard. A more modern projectile might be able to keep most of the penn while giving back some terminal effect. 7mm-08 is still too heavy recoiling for full auto fire in a light carbine and in terms of weight and size isn't any better than the 308. Anti Material? 7.62x51 doesn't do much there either, for that you have .50BMG.

 

[meketrefe]

Eh, I don't really agree. This round was specifically designed for penetration, it exceeds the 7.62x51 in that regard. A more modern projectile might be able to keep most of the penn while giving back some terminal effect. 7mm-08 is still too heavy recoiling for full auto fire in a light carbine and in terms of weight and size isn't any better than the 308. Anti Material? 7.62x51 doesn't do much there either, for that you have .50BMG.

Momentum, not penetration or energy. Penetration will not happen at long range anyway (speed at impact).

That is why even the previous phased out 5.56 punches through a thick hot rolled steel at 100 yards whereas the 7.62x39, Blackout and
a few others will fail. that is why slow moving 30 caliber rounds got phased out from service several decades ago.

Still, momentum is the key for a mid-weight and obviously heavy weight round.

The 308 is a decent car stopper. Of course if you have a 50 BMG even better but lets keep talking about small arms / infantry rifles and
light machine guns.

 

[meketrefe]

Certain alloys and auto glass are pretty tricky hard barriers.

When shit gets real there is no fucking around with 5.56 or AKs.

 

[Marine Cpl]

Everything is a compromise. There can never be one all purpose round to do everything. At 500 yards from mountain top to mountain top, the 5.56 will get there but it’ll be too slow to do the job it was designed for.

So let’s just keep it at .308 for everything then. Then you have issues at close ranges with recoil and weight for CQB. Dammit.

So let’s neuter the .308 for close ranges and develop the 7.62x39. Now we solved the close range issue. Great. But now our long range suffers.

Hey. Our enemy just developed a .22 calibered high speed round that’s way better than our 7.62x39 for short range Fuck. We have to do the same. There round is making it through our armor.

I got an idea. Let’s develop a 6 or 7mm. That way we can use it for everything. Cool. Hey wait a minute. Our enemy is still using a .308 at distance. The extra projectile weight is making it through barriers that our 6 or 7mm isn’t making it through.

Back to the drawing board.

It’s fine the way it is. Keep the 5.56 for close to medium grunt work and the .308 or bigger for long range designated marksman roles and crew served weapons. Within normal combat engagements at 200 yards or less, the 5.56 does the job. If you upgrade the 5.56 for the normal combat engagements of 200 yards or less, you’ll only get marginal improvement within those 200 yards. That marginal improvement comes at a cost. Less ammo and slightly more recoil. It’s not worth it if you are going to keep a higher calibered round for designated marksman, snipers, and crew served weapons for distance at over 300 yards anyway.

 

[meketrefe]

I got an idea. Let’s develop a 6 or 7mm. That way we can use it for everything. Cool. Hey wait a minute. Our enemy is still using a .308 at distance. The extra projectile weight is making it through barriers that our 6 or 7mm isn’t making it through.

Back to the drawing board.

Like I said, w/o going any further, the very same 7mm-08 does everything the 308 does but better, everything. So there would not be need to go to the drawing board.

The only exception would be 180gr-200gr bonded heavy loads for largest dangerous animals or moose at close range but those are very few exceptions
because most likely people will lean on the 30-06 or a magnum even a light one. Those bullets are too much for service use so in the average bullet weight
range the 7mm wins in any situation. One still has 175gr 7mm bullets that outperform the 175-185gr from a 308.

The thing is with the 308 modern solid bullets (including CNC) and modern powders there is less reason to justify the swap and even a lot less reason
to step into 6.5mm or 6mm. The 6mm should be dedicated to the light, compact rounds like the BR and little more.
Then at the same time in compact casings a 6mm 85-95gr in a compact casing would make a great infantry round.

There is a much stronger reason to up the 5.56 to 6mm than to down the 308.
The new 308 130gr service round is pretty effective and it has less recoil.