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The Case Against A General-Purpose Cartridge


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#141 Sebastian Balos

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Posted 04 December 2013 - 0622 AM

Where did you get that the fragmentation velocity is 2300 fps? M193 fragments at much higher velocities.

 

Simulations are nice, but real world field experience is much better.



#142 seahawk

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Posted 04 December 2013 - 1104 AM

 

 

 


 

2. Say soft body armour. Would that not influence the tendency of a bullet to jaw?

 

 

I don't know - I can't recall seeing any tests of that.

 

 

Should that not be taken into consideration for a future rifle round? For me performance against body armour is of equal importance to performance against todays enemies.



#143 rmgill

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Posted 04 December 2013 - 1148 AM

I've said as much, if you use a ballistic calculator on some velocity averages I've shown. M855 does not tend to fragment beyond 200-250m. Neither does M193. Neither does Mk. 262. Neither does 6.8 SPC (I am actually uncertain that 6.8 SPC FMJs fragment at any range, as the muzzle velocity is very close to the fragmentation velocity for M855, and I think the jacket is thicker). A lead-free GPC would most likely not fragment at any range.


Which means we're back to relying upon velocity retention and primary wound channel size based on caliber for the terminal effects upon the presumptive man sized target. 

5.56 is great at shorter ranges. It gets problematic at longer ranges. That you're able to hit doesn't help if the hits aren't effective. 
 
 

The problem here is not the perception that 5.56's terminal effectiveness leaves something to be desired, it's that you can't get a drastic improvement by doing fundamentally the same thing. Rifle wounds are severe because of their velocity and energy, and they lose both of these things at range. All rifles do. Criticizing 5.56 for not tumbling quickly enough, or not fragmenting past a certain range, or for going through a target without upsetting is off-base when what you're proposing is replacing it with a cartridge that will have all of these same problems, while pinning your hopes on forty thousandths of an inch.


But, larger projectiles retain velocity and thus energy due to conservation of momentum. They're not as fast to begin with so they have less drag per unit distance to deal with. So, at range it would seem that they're more effective.


7.62x39 often causes through and through wounds that can be easily treated. 7.62 NATO is also known to do this. All these cartridges are, on a fundamental level, similar. A 'roided up Grendel will not give magical results, even if it gives good performance.


Do we have any clear indications of what terminal effects are, say gelatin tests of 5.56 and 7.62 as well as the examples of notional GPC at 500 and 800 meter ranges would be?

Gelatin tests at point blank range give you a good idea of what the effects are at point blank range. What they are at range is what we're talking about here.


...But it may not have to. What's most important is penetration, and 5.56 does seem capable of doing that job, most of the time. Remember, at the turn of the last century, it was considered perfectly acceptable to be striking targets at the maximum ballistic range of a rifle, with less energy than many handguns of the time. The bullets penetrated, and that was enough. Likewise, even individual artillery fragments are relied upon to cause injury to enemy soldiers, when they have pitiful amounts of energy even at fairly close range.


Forgive me, but I seem to recall E5M complaining about 5.56 and barrier penetration in combat. Add that to the range issue and it has me wondering about the true effectiveness of fights at long range.

Given that riflemen do not cause most of the casualties in warfare,


Bzzt. This isn't the case in COIN is it? When they can reliably use what's available in the platoon or company, relying upon and advocating that the real weapon is the FO is missing a very important current point.

The infantry are not solely close in defense for the Field Artillery and Forward Air Observers.

#144 rmgill

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Posted 04 December 2013 - 1155 AM

Really, I am unimpressed. The line on Tony's experience was not an attack. When he corrected me, I thanked him for it. How many of my actual arguments have you addressed?


Child soldiers wasn't an attack but it was a very poor argumentative rebuttal.

The calculations on how much weight the GPC would add to the already considerable burden of the platoon? The problems of designing lead-free and tracer projectiles with the necessary sectional density and caliber?


Something to be noodled with. But I DID address the point about nominal weight in the platoon. If it takes 3 hits to put down a Taliban Fighter, are you saving weight over a cartridge that takes one hit to do so? I think not.

The ballooned weight and size of the cartridge? The significant recoil and necessity of using muzzle brakes to control such a rifle in fully automatic fire (which I, at least, consider to be a disqualification, since automatic fire and flash hiders are two enormous tactical advantages)? Not a one.

 
Which forces are firing basic infantry rifles in combat at 500+ meter ranges in automatic mode? Seems like, if you're shooting at Taliban in the hills, you're all going to be taking single aimed shots and the only automatic fire will be from the Section or Platoon Automatic weapons, which will be heavier, firing from Bipods and be firing at targets of key importance.

Your regard for the terminal effectiveness of rifles against persons of smaller stature borders on the obsessive. Rifles do very little of the killing in war, and one might think it very strange indeed that someone would so adamantly insist that a rifle's caliber be changed to one hypothetically more effective against scrappy third world armies, given the enormous number of other advantages Coalition armed forces possess in that scenario.


When most of those advantages are not able to be used due to ROE, which multiple posters here have discussed in detail, then you're ignoring key facts about the environment.

If one were seriously concerned, perhaps a more reasonable solution than disrupting critical war supplies could be proposed, such as issuing ammunition loaded with projectiles intended for theaters where the enemy hasn't signed the first Hague Convention. The USMC is definitely not doing just that.


That like the ROE are political and not easily solved with engineering and application of money.

#145 BabyOlifant

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Posted 04 December 2013 - 1911 PM

Where did you get that the fragmentation velocity is 2300 fps? M193 fragments at much higher velocities.

 

Simulations are nice, but real world field experience is much better.

 

Minimum fragmentation velocity. Bullets do not suddenly start to fragment once they hit a certain velocity, they fragment more as the velocity goes up. The velocity at which M193's jacket begins to significantly deform and shed lead chunks is just below 2,300 ft/s, according to one PDF which seems to have been taken off the 'net. I have it somewhere in my archives, but I am not at home right now, so it will have to wait. However, here is an image that is from a similar test:

4cb181ba.jpg

 

M855 is much the same, which makes sense, considering they have basically the same center of gravity and jacket construction.

 

 

 

I've said as much, if you use a ballistic calculator on some velocity averages I've shown. M855 does not tend to fragment beyond 200-250m. Neither does M193. Neither does Mk. 262. Neither does 6.8 SPC (I am actually uncertain that 6.8 SPC FMJs fragment at any range, as the muzzle velocity is very close to the fragmentation velocity for M855, and I think the jacket is thicker). A lead-free GPC would most likely not fragment at any range.


Which means we're back to relying upon velocity retention and primary wound channel size based on caliber for the terminal effects upon the presumptive man sized target. 

5.56 is great at shorter ranges. It gets problematic at longer ranges. That you're able to hit doesn't help if the hits aren't effective. 
 
 

The problem here is not the perception that 5.56's terminal effectiveness leaves something to be desired, it's that you can't get a drastic improvement by doing fundamentally the same thing. Rifle wounds are severe because of their velocity and energy, and they lose both of these things at range. All rifles do. Criticizing 5.56 for not tumbling quickly enough, or not fragmenting past a certain range, or for going through a target without upsetting is off-base when what you're proposing is replacing it with a cartridge that will have all of these same problems, while pinning your hopes on forty thousandths of an inch.


But, larger projectiles retain velocity and thus energy due to conservation of momentum. They're not as fast to begin with so they have less drag per unit distance to deal with. So, at range it would seem that they're more effective.


7.62x39 often causes through and through wounds that can be easily treated. 7.62 NATO is also known to do this. All these cartridges are, on a fundamental level, similar. A 'roided up Grendel will not give magical results, even if it gives good performance.


Do we have any clear indications of what terminal effects are, say gelatin tests of 5.56 and 7.62 as well as the examples of notional GPC at 500 and 800 meter ranges would be?

Gelatin tests at point blank range give you a good idea of what the effects are at point blank range. What they are at range is what we're talking about here.


...But it may not have to. What's most important is penetration, and 5.56 does seem capable of doing that job, most of the time. Remember, at the turn of the last century, it was considered perfectly acceptable to be striking targets at the maximum ballistic range of a rifle, with less energy than many handguns of the time. The bullets penetrated, and that was enough. Likewise, even individual artillery fragments are relied upon to cause injury to enemy soldiers, when they have pitiful amounts of energy even at fairly close range.


Forgive me, but I seem to recall E5M complaining about 5.56 and barrier penetration in combat. Add that to the range issue and it has me wondering about the true effectiveness of fights at long range.

Given that riflemen do not cause most of the casualties in warfare,


Bzzt. This isn't the case in COIN is it? When they can reliably use what's available in the platoon or company, relying upon and advocating that the real weapon is the FO is missing a very important current point.

The infantry are not solely close in defense for the Field Artillery and Forward Air Observers.

 

 

1. This is true of all calibers. No one has yet, to my satisfaction, proven that a forty thousandths inch increase in caliber will greatly improve effectiveness. My suspicion is that it will not.

2. So? That doesn't change the mechanics of wounding. The GPC can retain all the energy it wants; if it icepicks through the target at 800m and deposits 50 J, it will do much the same to the target as 5.56mm, but cost 70% more in terms of weight.

3. This is a good point you bring up. The study I mentioned above in response to Sebastian's post does concern 7.62 NATO as well. I will endeavor to post it here for the thread.

4. Barrier penetration is a complex topic. 5.56 performs basically as well as 7.62x39 against some targets, like cinderblocks or trees, but much less well against others, like bricks. I suspect this has more to do with fragmentation than anything else. M855 has much the same sectional density as M43, but M43 has a steel jacket and operates at much lower velocity. You can improve 5.56 in this regard, but you're sacrificing terminal effectiveness. The same is true for a GPC. TANSTAAFL.

 

5. I sincerely doubt that, even in COIN, the majority of casualties are caused by rifles. Many other much more effective weapons are in play. Besides, this borders dangerously on an argument about whether the current method is a good way to fight asymmetric wars or not, and I'd rather not have that discussion.


Edited by BabyOlifant, 04 December 2013 - 2349 PM.


#146 BabyOlifant

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Posted 04 December 2013 - 1912 PM

 

Really, I am unimpressed. The line on Tony's experience was not an attack. When he corrected me, I thanked him for it. How many of my actual arguments have you addressed?


Child soldiers wasn't an attack but it was a very poor argumentative rebuttal.

The calculations on how much weight the GPC would add to the already considerable burden of the platoon? The problems of designing lead-free and tracer projectiles with the necessary sectional density and caliber?


Something to be noodled with. But I DID address the point about nominal weight in the platoon. If it takes 3 hits to put down a Taliban Fighter, are you saving weight over a cartridge that takes one hit to do so? I think not.

The ballooned weight and size of the cartridge? The significant recoil and necessity of using muzzle brakes to control such a rifle in fully automatic fire (which I, at least, consider to be a disqualification, since automatic fire and flash hiders are two enormous tactical advantages)? Not a one.

 
Which forces are firing basic infantry rifles in combat at 500+ meter ranges in automatic mode? Seems like, if you're shooting at Taliban in the hills, you're all going to be taking single aimed shots and the only automatic fire will be from the Section or Platoon Automatic weapons, which will be heavier, firing from Bipods and be firing at targets of key importance.

Your regard for the terminal effectiveness of rifles against persons of smaller stature borders on the obsessive. Rifles do very little of the killing in war, and one might think it very strange indeed that someone would so adamantly insist that a rifle's caliber be changed to one hypothetically more effective against scrappy third world armies, given the enormous number of other advantages Coalition armed forces possess in that scenario.


When most of those advantages are not able to be used due to ROE, which multiple posters here have discussed in detail, then you're ignoring key facts about the environment.

If one were seriously concerned, perhaps a more reasonable solution than disrupting critical war supplies could be proposed, such as issuing ammunition loaded with projectiles intended for theaters where the enemy hasn't signed the first Hague Convention. The USMC is definitely not doing just that.


That like the ROE are political and not easily solved with engineering and application of money.

 

 

1. Fine.

 

2. This is the sort of CoD-kiddie logic that makes these arguments so exasperating. I was hoping to have a better discussion than this.

 

3. Yeah, because that's totally what I said.

 

4. Really, this is getting old. Just because your ROE is bad does not mean you go back to massed Springfields engaging in 3000m indirect fire shots. If your ROE is broken, fix your ROE. If you can't do that, find another way around it (Carl Gustafs, or IDF tables for M240s, for instance). Trying to shoehorn basic infantry rifles into doing the job of the mortar is absurd, and I cannot take these arguments seriously. Should we equip them with volley sights, as well?

 

5. The USMC seems to think it is. Besides, how do you reckon it'll be easier to get all of NATO/ICAF to adopt an entirely new cartridge? Gimme a break.


Edited by BabyOlifant, 04 December 2013 - 2049 PM.


#147 BabyOlifant

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Posted 04 December 2013 - 1914 PM

Found this while archive-diving: BRL believes that energy deposition is the primary factor in incapacitation.


Edited by BabyOlifant, 04 December 2013 - 2314 PM.


#148 Sebastian Balos

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Posted 05 December 2013 - 0304 AM

@BabyOlifant

 

Fragmentation at 2139 fps, at 2555 and at 3192 fps is not the same. At 2139 fps, only a couple of mm fragment is detached from the core, which may have, IMHO, an insignificant effect on stopping poser. The bullet main body fracture which occurs at 2523 fps may be effective, though. What's the velocity drop of M855

or M193?

 

Note the difference between 7.62 and 5.56 mm round cavities at pg.62. I suspect this beast was used in the assassination of the Serbian PM Djindjic in 2003., fired from, IIRC some 100 m.



#149 BansheeOne

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Posted 05 December 2013 - 0409 AM

7.62x39 often causes through and through wounds that can be easily treated. 7.62 NATO is also known to do this. All these cartridges are, on a fundamental level, similar. A 'roided up Grendel will not give magical results, even if it gives good performance.

 

German DM 11 Ball 7.62 mm NATO fragments much like 5.56 mm, so I don't really know why this particularly wounding mechanism should be caliber-dependent.

 

Military rifle bullet wound patterns

 

- by Martin L. Fackler

 

In addition to the full-metal-jacketed construction which makes them "military" bullets, the pointed ogival "spitzer" tip shape is shared by all modern military bullets. The obvious advantage of this streamlined shape is decreased air drag, allowing the bullet to retain velocity better for improved long-range performance. A modern military 7.62 mm bullet (with all-lead core) will lose only about one-third of its muzzle velocity over 467 m; the same weight bullet with a round-nose shape loses more than one-half of its velocity over the same distance.

 

[...]

 

Bullet mass and bullet striking velocity establish a bullet's potential; they set the limit on the tissue disruption it can produce. Bullet shape and construction determine how much of this potential is actually used to disrupt tissue; they are the major determinants of bullet effect. Far and away the most disruptive bullet of those described is the West German 7.62 NATO round. Its fragmenting behaviour maximises utilisation of its much higher potential (bullet mass well over twice that of any of the 5.56mm bullets and velocity only about ten percent less than theirs) for tissue disruption.

 

This author has not tested other European 7.62 NATO rounds, but the "NATO standards" apparently allow bullet designers great latitude in the choice of bullet jacket material and thickness. In 1979 a published high-speed x-ray photograph showed the Swedish 7.62 equivalent to the 7.62 NATO bullet breaking in a soap block shot at a range of 100m. Although bullet fragments were not recovered and photographed (the importance of bullet fragmentation in tissue disruption was not well recognised at the time), one must suspect the same very disruptive behaviour from this bullet as from the West German round. This is particularly ironic since the Swedish wound ballistics program was using every means possible to discredit the M16 as "inhumane" while, at the same time, Sweden was producing a 7.62 mm military bullet that caused far more extensive wounds than the M16.

 

[...]

 

The design standards for ammunition that can be called "NATO" ammunition do not specify bullet jacket material or jacket thickness. The construction of the West German 7.62 mm NATO bullet differs from the US 7.62 mm NATO round in that, the jacket material is copper plated steel, whereas the US version is copper (or the so called gilding metal alloy, which is predominantly copper). The West German steel jacket is about 0.6mm thick near the cannelure and the US copper jacket is about 0.8mm thick at the same point. This design difference is responsible for a vast difference in performance in tissue. The German bullet, after travelling point-forward for only about 8 cm, yaws and breaks at the cannelure. The flattened point section retains only about 66 % of the bullet's weight, the remaining 45 % mass becomes fragments (Fig. 8). The wound profile can be described as an enlarged M16 profile (Fig. 3), with dimensions of the tissue disruption increased by 60 % (temporary stress cavity about 22 cm diameter; permanent crush cavity about 11 cm diameter, penetration depth of the bullet point about 58 cm). The uncomplicated thigh wound from this bullet is likely to have a large exit with the loss of substantial tissue near the exit; still, this might not be a very serious wound since the bullet fragmentation does not occur until beyond 10 cm penetration depth and, in most shots, the bullet will have passed well beyond the major vessels before this occurs. The abdomen shot, however, because of the much enlarged permanent cavity from bullet fragmentation, is likely to prove fatal in a majority of cases.

 

[...]

 

wund092aj.jpg

 

http://www.uthr.org/...nd_patterns.htm

 

http://www.men-defen...iew/?tx_men_pi1[detail]=130&cHash=8d1f8c6b926a98db6cb94a88d3808157


Edited by BansheeOne, 05 December 2013 - 0411 AM.


#150 rmgill

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Posted 05 December 2013 - 1428 PM

You can also do the Wood Tip thing like in .303. 

37-7.jpg



#151 BabyOlifant

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Posted 05 December 2013 - 1928 PM

@BabyOlifant

 

Fragmentation at 2139 fps, at 2555 and at 3192 fps is not the same. At 2139 fps, only a couple of mm fragment is detached from the core, which may have, IMHO, an insignificant effect on stopping poser. The bullet main body fracture which occurs at 2523 fps may be effective, though. What's the velocity drop of M855

or M193?

 

Note the difference between 7.62 and 5.56 mm round cavities at pg.62. I suspect this beast was used in the assassination of the Serbian PM Djindjic in 2003., fired from, IIRC some 100 m.

 

Re: non-constant fragmentation

I said as much, didn't I?

Re: velocity drop of M855 vs. M193

This is a difficult question to answer, because several values exist for the ballistic coefficient of M193. M855's BC is generally accepted to be .151 G7, and I have not found any samples that deviate significantly from this. However, some examples of M193 have a BC as low as .126 G7, while others, such as PMC's XP193 have a BC as high as .148 G7. If we use the lower value, M193 reaches 2,300 ft/s at 242 meters, and 2,500 ft/s at 189 meters. With the higher value, M193 reaches 2,300 ft/s at 284 meters, and 2,500 ft/s at 221 meters. This is from a 20" barrel, mind you.



#152 BabyOlifant

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Posted 05 December 2013 - 1929 PM

 

7.62x39 often causes through and through wounds that can be easily treated. 7.62 NATO is also known to do this. All these cartridges are, on a fundamental level, similar. A 'roided up Grendel will not give magical results, even if it gives good performance.

 

German DM 11 Ball 7.62 mm NATO fragments much like 5.56 mm, so I don't really know why this particularly wounding mechanism should be caliber-dependent.

 

I did not say it was.



#153 BabyOlifant

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Posted 05 December 2013 - 1930 PM

You can also do the Wood Tip thing like in .303. 

37-7.jpg

 

Of course. Keep in mind, though, that doing this tends to greatly increase the length of your bullet. With the GPC, perhaps not necessarily far enough to run into problems, but definitely something to remember.



#154 rathi

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Posted 07 December 2013 - 0859 AM

Any discussion about a GPC should consider the full spectrum of various small arms platform in use. Most current systems have the following concepts.

 

1) A magazine fed service rifle

2) A tripod mounted belt fed sustained fire machine gun

3) A squad weapon that is somewhere in between 1 and 2.

 

From a logistic perspective, belt and magazine ammunition are distinct even if they use the same cartridge. In my mind, that suggests two calibers, as they pay no logistical penalty provided each caliber is kept striclty magazine or belt fed only. The real question is whether the squad weapon should be magainze fed and share ammunition with the rifle or belt fed and share ammunition with the MMG.

 

The current needs for Afghanistan suggest long range firepower at the squad level. A bipod equipped MMG chambered in Tony's 6.5 GPC would be a solid option. It offers the range of a 7.62mm weapon but with much lower weight. It would be possible to reasonalby replacing both the Minimi and Mag with a single weapon, as well as eliminating 5.56 belt from the supply chain entirely.
 


Edited by rathi, 07 December 2013 - 0902 AM.


#155 BabyOlifant

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Posted 07 December 2013 - 1811 PM

Any discussion about a GPC should consider the full spectrum of various small arms platform in use. Most current systems have the following concepts.

 

1) A magazine fed service rifle

2) A tripod mounted belt fed sustained fire machine gun

3) A squad weapon that is somewhere in between 1 and 2.

 

From a logistic perspective, belt and magazine ammunition are distinct even if they use the same cartridge. In my mind, that suggests two calibers, as they pay no logistical penalty provided each caliber is kept striclty magazine or belt fed only. The real question is whether the squad weapon should be magainze fed and share ammunition with the rifle or belt fed and share ammunition with the MMG.

 

The current needs for Afghanistan suggest long range firepower at the squad level. A bipod equipped MMG chambered in Tony's 6.5 GPC would be a solid option. It offers the range of a 7.62mm weapon but with much lower weight. It would be possible to reasonalby replacing both the Minimi and Mag with a single weapon, as well as eliminating 5.56 belt from the supply chain entirely.
 

 

This is a reasonable concept to me, as long as one remembers two things:

1. In environments dissimilar to Afghanistan, 5.56mm SAWs tend to be generally superior to their larger caliber brethren. Both magazine-fed 5.56mm SAWs and belt-fed 7.62mm SAWs have been tried, and 5.56mm belt-fed SAWs found superior to both, except in environments like Afghanistan.

 

2.  The GPC offers relatively little over 7.62 weapons in the big scheme of things. Virtually any weapon chambered for the GPC can also be made in 7.62, and 7.62 isn't that much heavier or less efficient. Special consideration should be paid to the burden placed on ammunition factories in the United States and Britain. In both cases, one factory is expected to supply, by itself, a large army. Lake City and Radway Green are both barely keeping up. Forcing them to switch calibers in the middle of a war may be unfeasible.
 

If the concept is refined, it basically becomes "issue M240s instead of M249s when going into mountainous environments", which I suggest in my article.



#156 BabyOlifant

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Posted 08 December 2013 - 0157 AM

Question for Tony: If a cartridge was proposed that met or approached all of the requirements for the GPC, and had a muzzle velocity of 3,000 ft/s or higher, would you consider throwing your support behind it? If so, why? If not, why not?


Edited by BabyOlifant, 08 December 2013 - 0157 AM.


#157 Argus

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Posted 08 December 2013 - 0213 AM

The wooden core in .303 along with the aluminumn, bakerlite and papermache tips also used was about getting the logenst 

 

 

You can also do the Wood Tip thing like in .303. 

37-7.jpg

 

Of course. Keep in mind, though, that doing this tends to greatly increase the length of your bullet. With the GPC, perhaps not necessarily far enough to run into problems, but definitely something to remember.

 

 

That was the idea of the wood/aluminumn/bakerlite/paper tips in .303. A longer bullet for the same mass to improve the BC, while also shifting the CG back to facilitate yaw post impact. 

 

A difference of 40 thou in caliber might not be that great, but its the difference in frontal area and circumference which come in train that are of significance.

 

Since thou seem acceptable, just going on the nominal diameters 223+40 implies

Area: 39057.065 to 54325.21 

Cric : 700.58 to  826.24

 

shane



#158 TTK Ciar

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Posted 08 December 2013 - 0325 AM

Also, it should be noted that if the bullet does yaw while passing through organs, the permanent cavity volume would be much larger with GPC than .223 due to its greater length.  Comparing differences in caliber is only valid if no yawing is assumed.

 

Unfortunately that might be a valid assumption, since compositions which facilitate barrier penetration also inhibit yawing in flesh.



#159 BabyOlifant

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Posted 08 December 2013 - 0718 AM

The wooden core in .303 along with the aluminumn, bakerlite and papermache tips also used was about getting the logenst 

 

 

You can also do the Wood Tip thing like in .303. 

37-7.jpg

 

Of course. Keep in mind, though, that doing this tends to greatly increase the length of your bullet. With the GPC, perhaps not necessarily far enough to run into problems, but definitely something to remember.

 

 

That was the idea of the wood/aluminumn/bakerlite/paper tips in .303. A longer bullet for the same mass to improve the BC, while also shifting the CG back to facilitate yaw post impact. 

 

A difference of 40 thou in caliber might not be that great, but its the difference in frontal area and circumference which come in train that are of significance.

 

Since thou seem acceptable, just going on the nominal diameters 223+40 implies

Area: 39057.065 to 54325.21 

Cric : 700.58 to  826.24

 

shane

 

For the GPC, though, it presents a few problems, potentially. I'm not saying they're insurmountable, but if you intend to include projectiles like this, you must figure that into your calculations.

 

Also, it should be noted that if the bullet does yaw while passing through organs, the permanent cavity volume would be much larger with GPC than .223 due to its greater length.  Comparing differences in caliber is only valid if no yawing is assumed.

 

Unfortunately that might be a valid assumption, since compositions which facilitate barrier penetration also inhibit yawing in flesh.

 

I will address the second half of Argus's post along with TTK's:

As BRL says, it is the temporary cavity that is considered to have the greatest effect on the target in the moment of striking. I have noted before that this has yet to be proven without a doubt; but it is the assumption many if not most work under. The permanent cavity is significant, of course. However, does it affect the target beyond its immediate path? There is little evidence. Does even a forty percent increase in frontal area greatly increase your chance of striking something vital? That seems unlikely to me.

I will reiterate: It is not that I think these things cannot be possible. I think they are unproven, and to advocate the adoption of a totally new cartridge which would disrupt the necessary supply to forces engaged in war, based upon unfounded supposition is folly. The GPC advocacy likes to assume that it is 5.56 and SCHV that must prove itself, when in fact the concept has been in service for half a century. It is the GPC that must prove it is providing a benefit worth the cost. So far this has not been achieved.



#160 rathi

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Posted 08 December 2013 - 0813 AM

 

This is a reasonable concept to me, as long as one remembers two things:

1. In environments dissimilar to Afghanistan, 5.56mm SAWs tend to be generally superior to their larger caliber brethren. Both magazine-fed 5.56mm SAWs and belt-fed 7.62mm SAWs have been tried, and 5.56mm belt-fed SAWs found superior to both, except in environments like Afghanistan.

 

 

That seems to be the case. The point of the intermediate cartirdge is to try and mitigate the weight issue that comes with the 7.62

 

 

2.  The GPC offers relatively little over 7.62 weapons in the big scheme of things. Virtually any weapon chambered for the GPC can also be made in 7.62, and 7.62 isn't that much heavier or less efficient.

 

 A 6.5 GPC would weigh roughly 17 grams, putting it at 2/3 the weight of the m80. Furthermore, current MMGs like the MAG are very heavy at 12.5 kg. A reasonable estimate for a new MMG in the less powerful 6.5 would be around 8 kg. Assuming 1000 rounds carried, that is total weight savings of about 14 kilos per weapon. Compared a Minimi+1k rounds of m855, it weights 6kg more.

 

Special consideration should be paid to the burden placed on ammunition factories in the United States and Britain. In both cases, one factory is expected to supply, by itself, a large army. Lake City and Radway Green are both barely keeping up. Forcing them to switch calibers in the middle of a war may be unfeasible.

 

 

I would like to note that such an issue could be overcome if our procurement system were even halfway competent, but unfortunately you are correct.

 

If the concept is refined, it basically becomes "issue M240s instead of M249s when going into mountainous environments", which I suggest in my article.

 

 

The M240 is effective but comes at a serious weight penalty. The Poles are also in Afghanistan, equipped with significantly lighter PKM derrived MMGs chambered in 7.62 NATO.






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