.277 Fury/NGSW Round

[Some Guy]

Hello MDS Brain Trust,

I have a curiosity about the .277 Sig Fury round. I am not a re-loader or a bullet expert. According to some articles I've read, the Fury's casing is composed of a stainless steel base, an aluminum locking washer, and a brass case. The supposedly unique casing enables it to achieve extremely high pressures, and that is supposed to give the round a lot of energy.

My question is about a risk of galvonic corrosion from having different metals in contact during storage. I think in some conditions when aluminum is paired with brass it can result in galvonic corrosion. It's also possible with stainless steel and aluminum. Anyone have any thoughts about whether or not there might be a risk of this kind of corrosion in this particular casing?

This is just a curiosity about a new product that is going to in the field next year and possibly for decades after. I'm thinking about scenarios like storage conditions near marine or humid environments, especially for long periods. Or if a bunch of it is distributed and used by US military units in wet or humid conditions. I am wondering if the DOD buys a billion rounds of this stuff and stores a bunch of it for whatever use, will some of it be ineffective or dangerous if it's stored improperly?

Also, this round has a lot of energy, and would having a weakness at the aluminum washer & brass, or steel base & aluminum washer junction create safety issues? I'm wondering if improperly stored ammunition would result in some guns blowing up and personnel getting hurt. Is this ammunition going to require some white glove, no humidity storage for it to be reliably used in the field?

Any ideas on this one? Has anyone read anything about the .277 Fury testing or long term reliability testing data?

Maybe it would require specialized storage that would add to the cost of the program?

Some Guy

 

[Jimgoespewpew]

Just attach boat zincs to them

 

[jrumann59]

If you plan to push to those pressures you will need that case but from what I have seen the practice ammo and what is available is all brass with much lower pressures. No one besides the Army and Sig know what the barrel life would be in hot engagement where you are shooting 80K PSI rounds during year long military conflict. I have heard the barrel life to be around 12k rounds using the mil-spec cartridge.

 

[Park ranger]

I take my barrels off at:

223 , 3000 rounds
308, 5000
6.5 cm, 2500 rounds

With those. 277 pressures , I guess 700 round barrel life.

 

[Boats]

If you plan to push to those pressures you will need that case but from what I have seen the practice ammo and what is available is all brass with much lower pressures. No one besides the Army and Sig know what the barrel life would be in hot engagement where you are shooting 80K PSI rounds during year long military conflict. I have heard the barrel life to be around 12k rounds using the mil-spec cartridge.

12k seems optimistic, especially in automatic and belt fed.

 

[Some Guy]

If you plan to push to those pressures you will need that case but from what I have seen the practice ammo and what is available is all brass with much lower pressures. No one besides the Army and Sig know what the barrel life would be in hot engagement where you are shooting 80K PSI rounds during year long military conflict. I have heard the barrel life to be around 12k rounds using the mil-spec cartridge.

Thanks for the opinion on this. I would also guess that practice and some fielded ammunition will be all brass and sacrifice on some pressure. The round would still carry a lot of energy with an all-brass casing.

I also think that these weapons will require frequent barrel replacements.

I am starting to think the fielding of the XM7 may be similar to the M-16 fielding. They discovered issues with it that needed to be corrected. But these issues cost many lives.

I hope the DOD has learned from this experience and that the XM7 weapon and ammunition undergo a lot more testing before they are fielded; and that when they are fielded the users have access to a lot of training before they actually take the weapon and ammunition into combat. I don't want one US soldier, Marine, airman or sailor killed or wounded due to a weapon or round malfunction.

 

[jrumann59]

12k seems optimistic, especially in automatic and belt fed.

There is a "rumor" of something Sig did with the barrel lining that off-sets the wear but until it it actually gets into some units hands we are dealing with the "marketing" aspect of this gun.

Thanks for the opinion on this. I would also guess that practice and some fielded ammunition will be all brass and sacrifice on some pressure. The round would still carry a lot of energy with an all-brass casing.

I also think that these weapons will require frequent barrel replacements.

I am starting to think the fielding of the XM7 may be similar to the M-16 fielding. They discovered issues with it that needed to be corrected. But these issues cost many lives.

I hope the DOD has learned from this experience and that the XM7 weapon and ammunition undergo a lot more testing before they are fielded; and that when they are fielded the users have access to a lot of training before they actually take the weapon and ammunition into combat. I don't want one US soldier, Marine, airman or sailor killed or wounded due to a weapon or round malfunction.

The big thing will be what is the barrel. The system itself is not too different than off the shelf Sig systems available to the public. They made it so the operations of arms is similar to the M4 but with piston system and proprietary recoil system. Lower seems like pretty much AR15/M16 lower with a bunch of ambi stuff.

 

[Boats]

After reading more about the .277 Fury (6.8x51) I have some questions.

Specifically, I don't see the point. It is the same length and casing diameter as 7.62x51 (so mag capacity will be 20-25)

the bullets are lighter by 12grains (135 vs 147) so a 200 round load out will save a whopping 0.3lbs

The velocity is 3000fps. Which a light 7.62 can do without having to do huge pressures and steel backed casings. (Winchester 7.62x51 135gr sierra varminter @3000fps, for example)

So I fail to see the magic here. Or how this is a significant advantage over 7.62 black tip. This all seems like it could have been done with a bullet change (like a high BC monolithic or a steel penetrator) to 7.62 instead of an entirely new weapon system.

All that said, it isn't the barrel burner that initial reports made it out to be. There was talk for a while of velocities of 3200-3500fps.

 

[smdub]

I think the 80ksi is a long term game changer. You can either load any cartridge that much faster (the approach they are taking now), or make the whole cartridge smaller (imagine 7.62NATO equivalent loads in a 5.56 action/case length.) In essence with the hybrid case technology you could make any round faster. 50BMG, 338 lapua, 308win mag, etc. There is probably a practical lower limit as case head diameter goes down due to the volume you lose due to the internal locking ring.

Remember they are pushing a 135gr load to 3000fps in a 16" barrel. That last part is really key. 308 isn't doing that. The aforementioned Winchester Varmiter spec is likely using a 24" barrel.

 

[lazarus]

12k seems optimistic, especially in automatic and belt fed.

I can't speak to machine guns. In a regular rifle barrel, I'd think barrel life span would be low single digit thousands before throat erosion was a serious problem. chrome lined AR-15 barrels typically see somewhere around 10k rounds before accuracy starts dropping off. SS would be less. Melonited would probably be somewhat more. Fully automatic fire can easily cut that in half or third it. Now accuracy reducing and accuracy reduced enough to fall below mil spec and need replacing are different things.

MG barrels are much heavier and harder. But I'd still think on a belt fed, you might be talking also still just a few thousand rounds.

 

[USAF05]

Hello MDS Brain Trust,

I have a curiosity about the .277 Sig Fury round. I am not a re-loader or a bullet expert. According to some articles I've read, the Fury's casing is composed of a stainless steel base, an aluminum locking washer, and a brass case. The supposedly unique casing enables it to achieve extremely high pressures, and that is supposed to give the round a lot of energy.

View attachment 404577

My question is about a risk of galvonic corrosion from having different metals in contact during storage. I think in some conditions when aluminum is paired with brass it can result in galvonic corrosion. It's also possible with stainless steel and aluminum. Anyone have any thoughts about whether or not there might be a risk of this kind of corrosion in this particular casing?

This is just a curiosity about a new product that is going to in the field next year and possibly for decades after. I'm thinking about scenarios like storage conditions near marine or humid environments, especially for long periods. Or if a bunch of it is distributed and used by US military units in wet or humid conditions. I am wondering if the DOD buys a billion rounds of this stuff and stores a bunch of it for whatever use, will some of it be ineffective or dangerous if it's stored improperly?

Also, this round has a lot of energy, and would having a weakness at the aluminum washer & brass, or steel base & aluminum washer junction create safety issues? I'm wondering if improperly stored ammunition would result in some guns blowing up and personnel getting hurt. Is this ammunition going to require some white glove, no humidity storage for it to be reliably used in the field?

Any ideas on this one? Has anyone read anything about the .277 Fury testing or long term reliability testing data?

Maybe it would require specialized storage that would add to the cost of the program?

Some Guy

We already have a bunch of munitions that are sensitive to humidity factors. Generally, when small arms are packed in ammo cans from the manufacturer they are full to the brim and sealed. It is only when issuing ammo to units that we pop the seal (minus some periodic inspections), and then a bag or two of desiccant is added in the void of the can. There are measures in place such as humidity indicators on certain munitions containers that have a water sensitive paper that turns pink in the presence of moisture, giving you an overall quick look of the conditions inside the can without opening it. The tech experts will field it with proper tech data and receive feedback from the field on what is happening with the round and update guidance on how to store them in response to environmental factors.

 

[lazarus]

After reading more about the .277 Fury (6.8x51) I have some questions.

Specifically, I don't see the point. It is the same length and casing diameter as 7.62x51 (so mag capacity will be 20-25)

the bullets are lighter by 12grains (135 vs 147) so a 200 round load out will save a whopping 0.3lbs

The velocity is 3000fps. Which a light 7.62 can do without having to do huge pressures and steel backed casings. (Winchester 7.62x51 135gr sierra varminter @3000fps, for example)

So I fail to see the magic here. Or how this is a significant advantage over 7.62 black tip. This all seems like it could have been done with a bullet change (like a high BC monolithic or a steel penetrator) to 7.62 instead of an entirely new weapon system.

All that said, it isn't the barrel burner that initial reports made it out to be. There was talk for a while of velocities of 3200-3500fps.

You are missing what is so special about it. Not being dickish.

The BC is significantly higher. A 130gr 7.62x51 has run out of ass by 500yds. This sucker is a 1000yd round. It significantly extends possible engagement ranges. Additionally, that 3000fps is out of a 13.5" barrel. To get a 130gr 7.62x51 up to similar 3000fps velocity, you need about an 16-18" barrel. So you can have about the same OAL with a suppressor on as a typical M16 or AR-10 DMR. OR you can use it unsuppressed and the whole thing fits in the same box length an M-4 would. As GWOT, to a degree, and Ukraine-Russia is certainly showing us, suppressors are important. It also makes the whole carbine lighter, being able to be several inches shorter.

Next, you are forgetting that I think the case itself is also a bit lighter. Between the smaller neck and the SS base, rather than brass base. Okay, it is very little difference, but you are probably talking half a pound total, not .3lbs.

That higher BC also translates into much higher sectional density. About 15% higher for a 6.8 135gr than a 7.62 147gr. Higher sectional density, for a similar hardness bullet, leads to greater penetration of light armor, like body armor. And the much higher BC, leads to vastly superior light armor penetration at range. For the same armor that a 7.62x51mm black tip can penetrate at 50yds, 6.8x51 black tip likely could penetrate at 200yds. What that 7.62 black tip can penetrate at 200yds, a 6.8 black tip could likely penetrate at around 350-400yds. Anything you'd do for 7.62x51, you can do for 6.8x51 and better. Want a 175gr SMK to really reach out there with your .308/7.62x51 DMR? You could run 170gr 6.8s and extend the engagement range a solid 300-400yds further than your 175gr 7.62 SMK could. Want better penetration and use tungsten carbide penetrators? That 6.8 can do the same, and still have better penetration at all distances.

What is also missing on the barrel burning, is the throat. Sure, the velocity isn't that extreme. So the lands and crown aren't going to get worn out too bad, but the throat is being subject to the pressure and heat from 85k. So, I assume that the erosion there is going to be worse than pretty much anything else on the market.

I don't personally think this is such a miracle round and the Sig Spear isn't some miracle carbine. I get what Mil is going for. But I think even as limited issue, at best this is a HOT AF DMR, and maybe it might make a decent general purpose machine gun round. Maybe. You are dealing with lower capacity, so things like incendiary rounds will have slightly less impact, but it might not really matter. But issuing to entire units? Even just select units sounds like a bad idea. The recoil is still pretty much 7.62x51. Which is too much for your average infantryman to shoot as accurately at 5.56. And you are also still carrying either a lot more weight, or significantly reduced combat load, ~33% less. Sure Russia doesn't have as much body armor as one used to think they might, but I am not hearing a lot of reports out of Ukraine that service rifles are having an extremely difficult time against infantry. As is usual, artillery and grenades/RPGs and machine guns are accounting for a lot more injuries and deaths than rifles. Just like every war since the late 1800s. People can't be armored everywhere, and most people are going to have a moment of reflection if they get hit in the chest with a 5.56, even with level IV/ESAPI plates.

I can absolutely see the gain in a DMR role, extending effective engagement ranges. A 135gr 6.8x51 has about the same effective range as a 175gr SMK 7.62x51 AFAIK. A 150 or 160gr would have longer effective range. And the 135gr 6.8 would have a MUCH longer point-blank range than the 175 SMK 7.62x51 would have and generally far superior performance out to medium ranges like 500-600yds. Plus that better light armor penetration. So a GP machine gun would have more impact on armored infantry, as well as light armored vehicles.

 

[4g64loser]

Urinal gossip has sig using something akin to the stellite that was used in rear portion of M2 barrels (some, not all). But that's definitely unconfirmed report.

That said, pushing pressure up and using the round in high rate of fire will cause measurable erosion rapidly. The question becomes what is a tolerable standard of accuracy before replacement is indicated.

 

[lazarus]

We already have a bunch of munitions that are sensitive to humidity factors. Generally, when small arms are packed in ammo cans from the manufacturer they are full to the brim and sealed. It is only when issuing ammo to units that we pop the seal (minus some periodic inspections), and then a bag or two of desiccant is added in the void of the can. There are measures in place such as humidity indicators on certain munitions containers that have a water sensitive paper that turns pink in the presence of moisture, giving you an overall quick look of the conditions inside the can without opening it. The tech experts will field it with proper tech data and receive feedback from the field on what is happening with the round and update guidance on how to store them in response to environmental factors.

So long as we don't go all Russia with our munitions storage, we should be fine. You really need a condensing environment for galvanic corrosion to occur. So you'd need to dip below the dew point. Oxidation could occur. But even high relative humidity won't cause galvanic corrosion until condensation can actually form on the surface as there has to be an electrolyte present with water acting as the medium for the ions to exchange across. Keeping the humidity in check in the ammo containers would take care of that.

 

[USAF05]

So long as we don't go all Russia with our munitions storage, we should be fine. You really need a condensing environment for galvanic corrosion to occur. So you'd need to dip below the dew point. Oxidation could occur. But even high relative humidity won't cause galvanic corrosion until condensation can actually form on the surface as there has to be an electrolyte present with water acting as the medium for the ions to exchange across. Keeping the humidity in check in the ammo containers would take care of that.

Yea. Good point. we usually don't bring more than we operate with into an area anyway. Survive to Operate. But I'll leave it to the guys in lab coats to do the strategic science. I'm more day to day inspection and maintenance.

 

[lazarus]

Yea. Good point. we usually don't bring more than we operate with into an area anyway. Survive to Operate. But I'll leave it to the guys in lab coats to do the strategic science. I'm more day to day inspection and maintenance.

I did forget to add, yeah if you dropped the rounds in salt water, galvanic corrosion between the SS, aluminum, and brass will occur. But you are likely still talking the time span of weeks to cause serious issues. Just a regular freshwater environment like your pack/rig got rained on (several times) would likely take months for it to be a serious concern.

 

[Boats]

You are missing what is so special about it. Not being dickish.

The BC is significantly higher. A 130gr 7.62x51 has run out of ass by 500yds. This sucker is a 1000yd round. It significantly extends possible engagement ranges. Additionally, that 3000fps is out of a 13.5" barrel. To get a 130gr 7.62x51 up to similar 3000fps velocity, you need about an 16-18" barrel. So you can have about the same OAL with a suppressor on as a typical M16 or AR-10 DMR. OR you can use it unsuppressed and the whole thing fits in the same box length an M-4 would. As GWOT, to a degree, and Ukraine-Russia is certainly showing us, suppressors are important. It also makes the whole carbine lighter, being able to be several inches shorter.

Next, you are forgetting that I think the case itself is also a bit lighter. Between the smaller neck and the SS base, rather than brass base. Okay, it is very little difference, but you are probably talking half a pound total, not .3lbs.

That higher BC also translates into much higher sectional density. About 15% higher for a 6.8 135gr than a 7.62 147gr. Higher sectional density, for a similar hardness bullet, leads to greater penetration of light armor, like body armor. And the much higher BC, leads to vastly superior light armor penetration at range. For the same armor that a 7.62x51mm black tip can penetrate at 50yds, 6.8x51 black tip likely could penetrate at 200yds. What that 7.62 black tip can penetrate at 200yds, a 6.8 black tip could likely penetrate at around 350-400yds. Anything you'd do for 7.62x51, you can do for 6.8x51 and better. Want a 175gr SMK to really reach out there with your .308/7.62x51 DMR? You could run 170gr 6.8s and extend the engagement range a solid 300-400yds further than your 175gr 7.62 SMK could. Want better penetration and use tungsten carbide penetrators? That 6.8 can do the same, and still have better penetration at all distances.

What is also missing on the barrel burning, is the throat. Sure, the velocity isn't that extreme. So the lands and crown aren't going to get worn out too bad, but the throat is being subject to the pressure and heat from 85k. So, I assume that the erosion there is going to be worse than pretty much anything else on the market.

I don't personally think this is such a miracle round and the Sig Spear isn't some miracle carbine. I get what Mil is going for. But I think even as limited issue, at best this is a HOT AF DMR, and maybe it might make a decent general purpose machine gun round. Maybe. You are dealing with lower capacity, so things like incendiary rounds will have slightly less impact, but it might not really matter. But issuing to entire units? Even just select units sounds like a bad idea. The recoil is still pretty much 7.62x51. Which is too much for your average infantryman to shoot as accurately at 5.56. And you are also still carrying either a lot more weight, or significantly reduced combat load, ~33% less. Sure Russia doesn't have as much body armor as one used to think they might, but I am not hearing a lot of reports out of Ukraine that service rifles are having an extremely difficult time against infantry. As is usual, artillery and grenades/RPGs and machine guns are accounting for a lot more injuries and deaths than rifles. Just like every war since the late 1800s. People can't be armored everywhere, and most people are going to have a moment of reflection if they get hit in the chest with a 5.56, even with level IV/ESAPI plates.

I can absolutely see the gain in a DMR role, extending effective engagement ranges. A 135gr 6.8x51 has about the same effective range as a 175gr SMK 7.62x51 AFAIK. A 150 or 160gr would have longer effective range. And the 135gr 6.8 would have a MUCH longer point-blank range than the 175 SMK 7.62x51 would have and generally far superior performance out to medium ranges like 500-600yds. Plus that better light armor penetration. So a GP machine gun would have more impact on armored infantry, as well as light armored vehicles.

I can understand that. Thanks for the insight.

I can't say I'm a huge fan, but I can see some advantage and disadvantage better now. Thanks.

 

[Some Guy]

We already have a bunch of munitions that are sensitive to humidity factors. Generally, when small arms are packed in ammo cans from the manufacturer they are full to the brim and sealed. It is only when issuing ammo to units that we pop the seal (minus some periodic inspections), and then a bag or two of desiccant is added in the void of the can. There are measures in place such as humidity indicators on certain munitions containers that have a water sensitive paper that turns pink in the presence of moisture, giving you an overall quick look of the conditions inside the can without opening it. The tech experts will field it with proper tech data and receive feedback from the field on what is happening with the round and update guidance on how to store them in response to environmental factors.

Thanks. This is good information.

 

[Some Guy]

We already have a bunch of munitions that are sensitive to humidity factors. Generally, when small arms are packed in ammo cans from the manufacturer they are full to the brim and sealed. It is only when issuing ammo to units that we pop the seal (minus some periodic inspections), and then a bag or two of desiccant is added in the void of the can. There are measures in place such as humidity indicators on certain munitions containers that have a water sensitive paper that turns pink in the presence of moisture, giving you an overall quick look of the conditions inside the can without opening it. The tech experts will field it with proper tech data and receive feedback from the field on what is happening with the round and update guidance on how to store them in response to environmental factors.

Also, if this round is adopted in the civilian market its users may need to follow this kind of storage practice. Again, good information. Thanks a lot.

 

[Some Guy]

So long as we don't go all Russia with our munitions storage, we should be fine. You really need a condensing environment for galvanic corrosion to occur. So you'd need to dip below the dew point. Oxidation could occur. But even high relative humidity won't cause galvanic corrosion until condensation can actually form on the surface as there has to be an electrolyte present with water acting as the medium for the ions to exchange across. Keeping the humidity in check in the ammo containers would take care of that.

Thanks. More good information.