A better infantry round?
- Thread starter Scott Evans
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Badger Arms
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It's not just the bullet diameter, it's the design of the bullet, weight, and velocity.
In my opinion, we need the following characteristics:
6mm or .250 diameter bullet
Weight of 80-100 gr
Ballistic Coefficient of greater than .500
Velocity of at least 2700 fps.
Steel penetrator in front of lead core designed to separate in soft tissue. This requires a thin jacket and less-than-optimum rotational velocity.
Other cool things to have:
Blackened brass for stealth.
Low-friction coating on bullets (must not be sticky)
Closed bullet base to prevent vaporized lead hazard.
Tracer round with identical BC, Balance, and Weight.
In the long run, we will probably never see anything other than a 5.56x45mm improved round if even that. Too bad.
In my opinion, we need the following characteristics:
6mm or .250 diameter bullet
Weight of 80-100 gr
Ballistic Coefficient of greater than .500
Velocity of at least 2700 fps.
Steel penetrator in front of lead core designed to separate in soft tissue. This requires a thin jacket and less-than-optimum rotational velocity.
Other cool things to have:
Blackened brass for stealth.
Low-friction coating on bullets (must not be sticky)
Closed bullet base to prevent vaporized lead hazard.
Tracer round with identical BC, Balance, and Weight.
In the long run, we will probably never see anything other than a 5.56x45mm improved round if even that. Too bad.
benewton
Member
Last I knew, or read, the 7MM was the ballistics champ.
That said, I think smaller cases are better, and, with heavier/larger rounds, given standard combat conditions, it's not necessary to put 3KFPS.
I'm for the 6X45MM or 6MM/.223, as you prefer.
The weapon's ergonomics work, or so I was trained, and the ballistics match what's going on for most of the grunts.
So if I gotta take one for general issue...
Else, I take the M1A NM.
That said, I think smaller cases are better, and, with heavier/larger rounds, given standard combat conditions, it's not necessary to put 3KFPS.
I'm for the 6X45MM or 6MM/.223, as you prefer.
The weapon's ergonomics work, or so I was trained, and the ballistics match what's going on for most of the grunts.
So if I gotta take one for general issue...
Else, I take the M1A NM.
Chris Rhines
Member
The 6x45 has been tried (actually, it might have been a 6x44.) Called the 6mm Wheeler, and was designed from the outset as a more-powerful cartridge for the AR-15 package. If I remember right, it put out a 75grn 6mm slug at 3200fps. Nice, but the short overall length (required for AR mags) limited it's ME to 1700fpe. Not quite enough for a battle rifle, to my mind, but close.
I'd prefer to use an intermediate case diameter and stretch out the case length until you get the right power level (ideal, 2100fpe at the muzzle and 1000fpe 500 yards downrange.)
Badger - I like your requirement list, but is it even possible to make a 6mm bullet with a .500 BC?
- Chris
I'd prefer to use an intermediate case diameter and stretch out the case length until you get the right power level (ideal, 2100fpe at the muzzle and 1000fpe 500 yards downrange.)
Badger - I like your requirement list, but is it even possible to make a 6mm bullet with a .500 BC?
- Chris
Badger Arms
Member
Berger Bullets lists a 95gr bullet at .524 BC if I remember correctly. These are VLD bullets. VLD (Very Low Drag) is a bullet optimized for its BC rather than optimized for accuracy and manufacturing ease (Flat Based) or the compromise Boat Tailed bullet you see in the standard M855/SS109 round. VLD bullets can be made very easily and cost just a little more than regular bullets.
http://www.bergerbullets.com/catalog.htm
http://www.bergerbullets.com/catalog.htm
cratz2
Member
I don't know... not saying the 6x45 would be ideal but for ease of deployment (retaining all our M16/M4s and magazines with a barrel change and some tweaking) I think a 75 Gr BTHP 6mm bullet at 2700 or 2800 fps would be worlds more effective on soft targets than a 55 Gr FMJ 5.56 bullet at 3200 fps or a 62 Gr at 2900 fps.
Badger Arms
Member
Can you get a 75gr bullet going 2700 fps from a 14" Barreled M-4 carbine though?
One of the problems in keeping the M16 is that you can't increase the pressure or change the pressure curve. The new 6.8 MM for the M16 platform is heavily dependant on a specific propellant. If the pressure curve is too long or too short you will get malfunctions. Remember the Vietnam war problems with bad ammo. It is not a good idea to have a military cartridge which is dependant on a sole source of gunpowder. You also cannot change the size or shape of the cartridge if you use the same mags.
I do not want to leave the impression that the ONLY M16 problem was the ammo. It is true that the military contractor for the rifle faked the QC, defrauded the US govt and got many troops killed. It is also true that we (grunts) were prohibited from writing to our congressman to complain. The Army ran a coverup for the defense contractor.
I do not want to leave the impression that the ONLY M16 problem was the ammo. It is true that the military contractor for the rifle faked the QC, defrauded the US govt and got many troops killed. It is also true that we (grunts) were prohibited from writing to our congressman to complain. The Army ran a coverup for the defense contractor.
Chris Rhines
Member
A self-regulating gas system for the M16 would be really nice. A self-regulating gas system for any rifle would be really nice.
Badger - Kewl!
A 95grn. bullet should be able to make 2700fps from a much smaller case than the 7.62x51. Hmmm. Punch this into the ol' ballistics program and...
We get an ME of 1538fpe. Seems a little bit on the low side, although it retains over 700fpe at 500 yards - wow! It seems like you could get that kind of energy out of a blown-out 5.56x45 case.
- Chris
Badger - Kewl!
A 95grn. bullet should be able to make 2700fps from a much smaller case than the 7.62x51. Hmmm. Punch this into the ol' ballistics program and...
We get an ME of 1538fpe. Seems a little bit on the low side, although it retains over 700fpe at 500 yards - wow! It seems like you could get that kind of energy out of a blown-out 5.56x45 case.
- Chris
Steve,
I am NOT speaking of the .243 Winchester, but of the new cartridge described as the ".243 Winchester Super Short Magnum". This has the same case as the .223 WSSM, which is considerably shorter and fatter than the 5.56x45mm case.
While I'm at it, I think everyone in my army would have an 18" bl rifle with sliding stock, except for the SDM's (2 per squad), who would each have optically sighted 24" bls.
John
I am NOT speaking of the .243 Winchester, but of the new cartridge described as the ".243 Winchester Super Short Magnum". This has the same case as the .223 WSSM, which is considerably shorter and fatter than the 5.56x45mm case.
While I'm at it, I think everyone in my army would have an 18" bl rifle with sliding stock, except for the SDM's (2 per squad), who would each have optically sighted 24" bls.
John
Badger Arms
Member
Reading up on it, "Cartridges of the World" lists some pretty interesting data. Two cartridges stand out. One is the 6mm International. This is a shortened and necked down 250 Savage. The problem with this is that it has too much case taper to feed reliably from the straight/curved M-16 magazine. If you blow out the case taper a bit and then replace the bolt/barrel you are in. Problem is that you can't get as many rounds into the magazine. Solve the problem by redesigning the magazine. Use stainless steel and blacken or teflon coat it. The M16 Magazine has a ton of extra space in it and can easilly accomodate a greater diameter round.
Second round is the old 6mm SAW from the 70's. Problem with this round is that it was too long and not quite as powerful. You could blow the case taper out to match that of the 5.56. The would probably edge it over the 2700 fps velocity that I like.
Why 2700 fps? Well, any slower and you have trajectory problems. Any faster and you start getting some serious controlability problems. You also get a greater sacrafice in terms of velocity when you use a shorter barrel. Just my opinion.
Second round is the old 6mm SAW from the 70's. Problem with this round is that it was too long and not quite as powerful. You could blow the case taper out to match that of the 5.56. The would probably edge it over the 2700 fps velocity that I like.
Why 2700 fps? Well, any slower and you have trajectory problems. Any faster and you start getting some serious controlability problems. You also get a greater sacrafice in terms of velocity when you use a shorter barrel. Just my opinion.
Nightcrawler
Member
Opinion? That's an honest-to-God fact.
But I agree, and so do the US Marines, apparently. They chose the 20" barreled M16A4 as their new weapon of choice. I can almost hear the Gun Shop Commandos wailing now, "but that weapon is too long and unweildy for urban use!"
Hey, I like carbines too, but if it comes down to a tradeoff between optimum ballistics and having a slightly handier weapon, ballistics wins my vote.
Badger Arms
Member
You're right, that's a fact, not an opinioin. What is also interesting is that all of these gun shop commandos have never really been in combat and/or have deep-seated prejudices one way or the other. I find no difficulty weilding an 18" barreled shotgun as I have both on duty and off. I can understand that if you are clearing a house, you might want a 14" barrel. I'd also want to put at least a 3rd burst into the Bad Guy if I were in a house with him to make sure he's dead.
If others reading this didn't understand what I meant with the velocity and barrel length, here goes:
The faster the initial velocity, the greater effect barrel length will have on velocity. When you have a 20" barrel firing a 5.56x45 round at 3250fps you can expect a more severe penalty when you take 6" off that barrel than if you start with a 30 caliber projectile going 2400fps. That's why the AK-47 can have a 16" barrel and the 5.56 required a 20" barrel. That's why there are complaints about the M-4 carbine.
If others reading this didn't understand what I meant with the velocity and barrel length, here goes:
The faster the initial velocity, the greater effect barrel length will have on velocity. When you have a 20" barrel firing a 5.56x45 round at 3250fps you can expect a more severe penalty when you take 6" off that barrel than if you start with a 30 caliber projectile going 2400fps. That's why the AK-47 can have a 16" barrel and the 5.56 required a 20" barrel. That's why there are complaints about the M-4 carbine.
cratz2
Member
I doubt it. Of course, accurate information is hard to come by and they (6x45 and 6x47) aren't even very popular wildcats anymore. But I'd imagine most of the load data is from a 20" or longer barrel and the velocity usually listed for a 75 Gr bullet is 2900 fps for the 6x45 and 3000fps for the 6x47. The 6x47 with the right powder might get 2700 fps out of a 14" barrel but then you have a nearly .1" longer OAL.
One problem I see with the 223 and 243 WSSMs is they are really fat cases. Discounting the changes that would be probably required to make it work in an AR platform, you could probably only fit about 8 cartridges in a standard 30 round-length magazine. These things are noticably larger in diameter than a 308! I do think I read that someone as making an upper in or 300 WSM. I just don't think it (the 243 WSSM) is the right cartridge for military purposes.
CMcDermott
Member
Another possibility is the old 25 Remington, shorten the case to fit the M16 and raise the pressure to modern levels to provide performance. It's a rimless case, with a .422" case head and length of 2.04". Shorten it to 1.75" or so and it will fit the M16. Raise it's working pressure to 62,000 from it's old level of 45,000 and I think it will provide all of the performance needed to launch .257", 95 grain bullets to 2700 fps.
Reason for 5.56mm effectiveness
The old 55gr standard will still fragment just fine in a 1-7"twist barrel.
The rotational velocity makes them stable in AIR. It does not keep them stable in flesh, which is a denser medium. The reason for the fragmentation is that the bullet yaws, in tissue, and then breaks at the cannelure.
The 147gr 7.62mm NATO bullets yaw too, as do the .30-06 rounds, the distinction is that they fail to break, because the jacket is too thick. Some other NATO countries developed 7.62mm NATO rounds that DID break at the cannelure and performed like an enlarged 55gr 5.56mm round.
References:
http://www.firearmstactical.com/briefs13.htm
http://www.ammo-oracle.com/#m193orm855
-Morgan
Neither the 55gr, or 62gr 5.56mm bullets derive their effectiveness from the rotational velocity of the bullet. This is a myth, propgated by the early belief that the 5.56mm's tumbled IN flight.
The old 55gr standard will still fragment just fine in a 1-7"twist barrel.
The rotational velocity makes them stable in AIR. It does not keep them stable in flesh, which is a denser medium. The reason for the fragmentation is that the bullet yaws, in tissue, and then breaks at the cannelure.
The 147gr 7.62mm NATO bullets yaw too, as do the .30-06 rounds, the distinction is that they fail to break, because the jacket is too thick. Some other NATO countries developed 7.62mm NATO rounds that DID break at the cannelure and performed like an enlarged 55gr 5.56mm round.
References:
http://www.firearmstactical.com/briefs13.htm
http://www.ammo-oracle.com/#m193orm855
-Morgan
benewton
Member
From what I've read, the 7.62 also yaws a good deal later, and is normally outside the (target) body when it does.
Also, fragmentation and breakup, the reason for the effectiveness of the smaller rounds, requires velocity on target. Hence, the M4 problems.
Getting old, I guess, but I like the idea of a big hole all of the way through. 'course, I like more big holes better, so I guess I stay with the 6mm upgrade.
Think that the 6x47 might work best, but, since I've got one of the black ones, the 6x45 seems the best immediate upgrade, at least to me.
Also, fragmentation and breakup, the reason for the effectiveness of the smaller rounds, requires velocity on target. Hence, the M4 problems.
Getting old, I guess, but I like the idea of a big hole all of the way through. 'course, I like more big holes better, so I guess I stay with the 6mm upgrade.
Think that the 6x47 might work best, but, since I've got one of the black ones, the 6x45 seems the best immediate upgrade, at least to me.
atek3
Member
anyone know when the new 6.8x43 mm is going to be available?
atek3
atek3
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