The specs for your .61 sound excellent. Do you think it would be backwards compatible with current .50 bmg weapons?

In terms of down range performance, do you see the value of the .61 primarily in increasing penetration, or increasing incendiary payload?

If the projectile is of comparable length to a .50/ .50 neckess, would the increased penetrator mass of the .61 still increase penetration even if the cores are the same length?

I cannot help but repeat my view that a cartridge according to requirements should be chosen first.

After that, an "optimal"  (compromise of conflicting design goals) weapon should be designed around it.

In my view, it is usually overlooked that, in the long run, ammunition is the expensive item, not the weapon. The backwards compatibilty issue looks at a single weapon, more or less from the perspective similar to the private owner. He does not shoot enough to wear out the gun. He enjoys an unlimited life-cycle.  

But in military use, guns have to be reconditioned and even replaced on a routine basis. Life-cycle is really limited. We live in an environment with an industrial base which is most economical at mass production, not mimicking gunmaker style.    

Using backwards compatibility as the goal is by no means as cheap as it looks on first sight. At the same time it severely limits possibilities of achieving up to date ballistics.         

JPeelen said:

But in military use, guns have to be reconditioned and even replaced on a routine basis. Life-cycle is really limited. We live in an environment with an industrial base which is most economical at mass production, not mimicking gunmaker style.    

I agree for most of the weapons, but the M2HB is a special piece of hardware.

The French army is still using ~10,000 M2HB manufactured before 1944, and we used then heavily since the war in Indochina.

JPeelen said:

I cannot help but repeat my view that a cartridge according to requirements should be chosen first. After that, an "optimal"  (compromise of conflicting design goals) weapon should be designed around it.

I disagree.  In my view, the weapon and cartridge must be designed together as a system.

To design one without regard to the other, seems unlikely to produce the optimal results.

JPeelen said:

Using backwards compatibility as the goal is by no means as cheap as it looks on first sight. At the same time it severely limits possibilities of achieving up to date ballistics.

Normally I would agree, because for the last 100-plus years, backwards compatibility with existing weapons has rarely -- if ever -- been a real concern, let alone a military requirement.

In the mid-19th century some armies adopted new metallic cartridges to upgrade old muzzleloaders, but since then the practice has been to acquire new weapons for any new cartridge.

However, Emeric presents a good argument that the M2 Browning may be a special case, a unique exception to the rule.

"The French army is still using ~10,000 M2HB manufactured before 1944, and we used then heavily since the war in Indochina."

Thats awesome.

The US has had similar results - there was a discovery of one made in 1933 that was still in service and operating perfectly:

https://www.firearmsnews.com/editorial/oldest-m2-browning-50-caliber-mg-still-in-service/383060

I recall reading numerous anecdotal reports of guys in Iraq whose M2's receivers were marked 'General Motors' and 'Frigidaire' indicating WW2 manufacture.

The design seems to be so successful that it has essentially killed off any competition. As far as I can tell the only alternative .50 bmg machine gun is the STK50 from singapore?

https://www.stengg.com/media/30308/50mg-brochure.pdf

JPeelen said:

I cannot help but repeat my view that a cartridge according to requirements should be chosen first. After that, an "optimal"  (compromise of conflicting design goals) weapon should be designed around it.

Thats certainly the ideal...

The question is whether we will actually see that occur. Theres been talk of a desire for a 'GPC' type intermediary cartridge for 15+ years, yet theres yet to be any manufacturer step up to the plate and create an intermediary sized weapon. Perhaps the LWRC SIX8 as an exception. 

Meanwhile the cartridge we're seeing genuinely take off a bit militarily as a 5.56/7.62 alternative is 6.5 Creedmoor (and .260 Remington per Emeric for French SF.) The reason is that it offers enhanced ballistics with a simple barrel change. 

A superior round, but requiring a brand new series of assault rifles and LMG's to be developed to fire it, would likely still be a topic of debate on internet forums...

For a .50 replacement, the prospects of a 'perfect' cartridge are even grimmer. A rifle is complex, but at the end of the day, it's a rifle, which most small arms manufacturers are capable of designing and manufacturing. Whereas a Machine Gun is both much more complex and requires far more in terms of testing and long terms durability, and far fewer small arms companies are capable/familiar with producing them. Much less producing a HMG that could compete with the prolific, legendary, and beloved M2... that would be a risky R&D venture to undertake without a gov't contract behind it. And until the new weapon was developed, the new cartridge design could not be tested. 

Whereas if '.61 Emeric' is backwards compatible with .50 bmg weapons, that bad boy could be tested within a year and with a fraction of the R&D budget. Get a firearms company or even machine shop to turn a new .61 M2 barrel, neck up some .50 BMG brass, and lathe turn some brass .61 solids, and you're in testing mode. Thats of course a bit flipant in terms of the work involved, but its certainly a much easier prospect than creating a new cartridge brass, new bullet, and new automatic weapon all at once. 

The last issue is one of requirements. Since the .50 BMG/M2 is a sort of ballistic 'Swiss army knife' (never the perfect tool for the job, but a tool that works for many jobs in the field) it's hard to pin down what the requirement would be to optimize the cartridge for. Is the goal a lighter cartridge/weapon with comparable penetration to .50 API? Is the goal better supersonic range than .50 API? Better incindiary effect? More penetration? More power then .50 BMG but with smaller weapon than 20mm cannon? etc. 

In that light, ".61E" is potentially promising. Get a more powerful / more API round than current .50bmg, while keeping polymer cartridge weight comparable to current .50 bmg brass, and the ability to be used in legacy weapons / future .50 sized weapons and mounts. 

gatnerd said:

Thats certainly the ideal...

Perhaps I am missing something.  How is it "ideal" to design a cartridge in complete disregard for weapon characteristics like barrel length, feeding reliability, magazine capacity, etc?

gatnerd said:

The question is whether we will actually see that occur.

I would submit that we sorta have seen it happen with the 6.8 TVCM, which was designed without regard for what seems likely to be the acceptable barrel lengths of NGSW-R and AR.

gatnerd said:

Theres been talk of a desire for a 'GPC' type intermediary cartridge for 15+ years, yet theres yet to be any manufacturer step up to the plate and create an intermediary sized weapon.

Nearly all of the talk about an intermediate-length GPC has been in internet forums like this one. 

There's been little military interest in such a cartridge, and no real demand in the civilian market.

gatnerd said:

Perhaps the LWRC SIX8 as an exception. 

No.  The SIX8 receiver length is the same as that of 5.56 receivers.

That's because cartridge OAL of 6.8 SPC is the same as 5.56 NATO.

gatnerd said:

Do you think it would be backwards compatible with current .50 bmg weapons?

That will depends on the weapon manufacturing year, probably.

For example, ours M2HB from WWII are in perfect shape and could fire a regular diet of M33/M8 ammo (working at 280-290 MPa) all day long, but if you feed them with some Short-Range Training Ammo (SRTA) running at 350-380 MPa, you will break the bolt locking lug after around 4,000 rounds, even if the STANAG allows for a MAP + 3 SD < 445 MPa.

Current production M2HB are OK with those SRTA ammo.

gatnerd said:

In terms of down range performance, do you see the value of the .61 primarily in increasing penetration, or increasing incendiary payload?

Payload ! Just like the 20 mm MG151 versus the 15 mm version, or the 20x102 vs. the 14.5x114.

If you want to increase the penetration while keeping the .50 "Form Factor", then the .460 Steyr or the .416 Barrett are the way to go (similar core length, but higher MV and better BC, so much more impact velocity).

EmericD said:

Payload ! Just like the 20 mm MG151 versus the 15 mm version, or the 20x102 vs. the 14.5x114. If you want to increase the penetration while keeping the .50 "Form Factor", then the .460 Steyr or the .416 Barrett are the way to go (similar core length, but higher MV and better BC, so much more impact velocity).

In terms of ground use, what would be the primary goal/effect of increasing the payload? Would it be for improving the ability to set cars/technicals on fire over current .50? And is the current .50 lacking in that regard? Or would the payload offer some other benefit, such as improving the ability to shatter/smash through walls and concrete? 

In terms of concrete penetration, is the rule similar to steel and ceramic,  where core length is paramount? 

Great info on SRTA/pressure on bolt life.

One bureaucratic snafu on the .61. Being over .60, that would make it a light cannon, rather than a machine gun by US military definition.

Other than that, it would be awesome!