6.2mm OCC
- Thread starter deadduck357
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Dr. Tad Hussein Winslow
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- Nov 14, 2007
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Needs some polish, but looks pretty sound. Need to add "full-auto controllability" in list of requirements.
I have long suspected that the "optimum" all-purpose combat round bullet diameter (a la 6.5 G and 6.8 S, etc.) should be either 6mm or .257, not 6.5mm or .277, for quantum leaps in bullet BC and SD, but yet with very little reduction in velocity (to maintain the bullet yawing result), and very little added to overall cartridge weight.
In other words, the optimum caliber (if there IS one better than 5.56x45) is much closer to the current 5.56 round than the current leading "contenders". 87 grains whizzing along past 2700 is gonna hurt, I guarantee ya, if you can actually obtain that!
The caliber should be .243 or .257, seems to me. The rest (case design) is nitpicking details, but it's obviously gonna be in the 40-45mm case length range, to fit in current platforms.
Does your parent case (the SAW) have less case taper than the chinese round, as it appears?
I have long suspected that the "optimum" all-purpose combat round bullet diameter (a la 6.5 G and 6.8 S, etc.) should be either 6mm or .257, not 6.5mm or .277, for quantum leaps in bullet BC and SD, but yet with very little reduction in velocity (to maintain the bullet yawing result), and very little added to overall cartridge weight.
In other words, the optimum caliber (if there IS one better than 5.56x45) is much closer to the current 5.56 round than the current leading "contenders". 87 grains whizzing along past 2700 is gonna hurt, I guarantee ya, if you can actually obtain that!
The caliber should be .243 or .257, seems to me. The rest (case design) is nitpicking details, but it's obviously gonna be in the 40-45mm case length range, to fit in current platforms.
Does your parent case (the SAW) have less case taper than the chinese round, as it appears?
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Amen brother. I think I posted a few years ago several times that the 6mm is it. You've really worked out what I have had rattling in my skull for awhile. Where can I buy one? You should have the rifle and 100 rounds of ammo made and shipped to the proving grounds.
Maverick223
Member
I like it, but you need to call it the 6mm OCC...the 6.2mm is misleading and just about turned me off from the sound of it (lack of boolits). Also I think the 6.5Grendel will have you beat for LR trajectory...prove me wrong and the world will soon follow. 
...and Welcome to THR!
...and Welcome to THR!
rangerruck
Member
with the bullet nose coming that close to the front of the mag, you are asking for probs; mainly from gi's in a hurry trying to load them, especially in combat situations, and messing them up, having them jam up, having the tighter clearances getting jammed up with debris, etc. etc.
Otherwise, I am all about a 6mm 70 to 80 grain bullet do 3k. what about the old Savage hipower, either the case or the bullet?
Otherwise, I am all about a 6mm 70 to 80 grain bullet do 3k. what about the old Savage hipower, either the case or the bullet?
deadduck357
Member
Dr. TAD, yes the taper is quite a bit less.
deadduck357
Member
Ranger, Maximum COAL for a m16/AR-15 mag is 2.260", I have it loaded at 2.250" plenty room to spare.
deadduck357
Member
Maveric, the .243 is 6.17mm, 6.2 is closer to correct than 6mm. Plus there are way to many 6mm cartridges out there, thought it may stand apart.
Maverick223
Member
Right you are, but it sounds like a new boolit...which would be a problem. It may become a hangup with marketing.
What about external ballistics...I want numbers!
JASmith
Member
Good start!
I think you're right -- the case capacity should be somewhat greater that that of the 6.8. Have you measured or calculated it? How much greater than for the 6.5 and 6.8?
The case capacity will give a slightly more quantitative indication of any ballistic advantage the 6.2 OCC might bring.
The marksman load should be compared the the Mk262 (77 gr Sierra Matchking).
What ballistic advantage does the new cartridge bring?
The Grendel yields impressive ballistics -- trajectory equal to or better that the 7.62 NATO, especially at long range. The OCC promises more powder, so might do even better in the 6.5.
-- Would be nice to get velocity and trajectory estimates for the OCC in 6.2, .25, and 6.5 bullets. The comparison would help cement selection of a particular caliber.
I think you're right -- the case capacity should be somewhat greater that that of the 6.8. Have you measured or calculated it? How much greater than for the 6.5 and 6.8?
The case capacity will give a slightly more quantitative indication of any ballistic advantage the 6.2 OCC might bring.
The marksman load should be compared the the Mk262 (77 gr Sierra Matchking).
What ballistic advantage does the new cartridge bring?
The Grendel yields impressive ballistics -- trajectory equal to or better that the 7.62 NATO, especially at long range. The OCC promises more powder, so might do even better in the 6.5.
-- Would be nice to get velocity and trajectory estimates for the OCC in 6.2, .25, and 6.5 bullets. The comparison would help cement selection of a particular caliber.
Whenever there was scientific effort to find the ideal combat cartridge they always came to 6.8-7mm. 6.2mm won't make much difference to worth the change.
As a combat cartridge you need a bit of wiggle room in terms of terminal performance. You can't put all your eggs in one basket.
A larger caliber, heavier bullet will have good terminal performance even beyond fragmentation. You can't base all your killing on fragmentation. We know how things work with military bullets. The ones that fragments good, won't penetrate good and vice versa. That's why I think this days people place too much weight on fragmentation and speed.
The higher the speed, the more barrel wear you'll get.
I think what you have there is a good cartridge for civilians. For military I don't think you get much over the 5.56mm to justify a change. The 5.56 can use 75 gr. bullets already.
So far the best new military cartridge for AR15 is the 6.8Spc. It could have been a lot better but this is pretty much the best you could get out of the AR15.
In my opinion, the next military cartridge shouldn't be limited by the 40 year old rifle you are going to have to replace soon anyway.
Is like buying a processor, for your next computer, that has to work in the old computer you have to replace. You waste money and get very little in return.
Once in a while you need to bite the bullet, start from the scratch and build something from the ground up. Something that looks in the future, not something that brings over half the shortcomings of the old design.
Every attempt to get the "next combat cartridge" was wasted by the same AR15 mag/magwell. Both, 6.5 Grendel and 6.8 Spc, are not everything they could have been, because they had to work in the small AR15 magwell.
I'm looking forward to the 7x46mm Murray. He may release the full specs in a couple of months.
As a combat cartridge you need a bit of wiggle room in terms of terminal performance. You can't put all your eggs in one basket.
A larger caliber, heavier bullet will have good terminal performance even beyond fragmentation. You can't base all your killing on fragmentation. We know how things work with military bullets. The ones that fragments good, won't penetrate good and vice versa. That's why I think this days people place too much weight on fragmentation and speed.
The higher the speed, the more barrel wear you'll get.
I think what you have there is a good cartridge for civilians. For military I don't think you get much over the 5.56mm to justify a change. The 5.56 can use 75 gr. bullets already.
So far the best new military cartridge for AR15 is the 6.8Spc. It could have been a lot better but this is pretty much the best you could get out of the AR15.
In my opinion, the next military cartridge shouldn't be limited by the 40 year old rifle you are going to have to replace soon anyway.
Is like buying a processor, for your next computer, that has to work in the old computer you have to replace. You waste money and get very little in return.
Once in a while you need to bite the bullet, start from the scratch and build something from the ground up. Something that looks in the future, not something that brings over half the shortcomings of the old design.
Every attempt to get the "next combat cartridge" was wasted by the same AR15 mag/magwell. Both, 6.5 Grendel and 6.8 Spc, are not everything they could have been, because they had to work in the small AR15 magwell.
I'm looking forward to the 7x46mm Murray. He may release the full specs in a couple of months.
deadduck357
Member
Jaws, how are you Quoting ? am I going blind caus I cant find a quote icon ?
But you are right my 6.2 OCC has less case capacity than the 6.8. But its not needed as its ballistics will exceed the 6.8spc. The 6.2 is pushing a lighter, smaller diameter bullet with better BC than the 6.8.
But you are right my 6.2 OCC has less case capacity than the 6.8. But its not needed as its ballistics will exceed the 6.8spc. The 6.2 is pushing a lighter, smaller diameter bullet with better BC than the 6.8.
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Maverick223
Member
Like this.
It is the "cartoonish" text bubble icon at the top of the quick reply (or advanced reply).
deadduck357
Member
A larger caliber, heavier bullet will have good terminal performance even beyond fragmentation. You can't base all your killing on fragmentation. We know how things work with military bullets. The ones that fragments good, won't penetrate good and vice versa. That's why I think this days people place too much weight on fragmentation and speed.
The higher the speed, the more barrel wear you'll get.
I think what you have there is a good cartridge for civilians. For military I don't think you get much over the 5.56mm to justify a change. The 5.56 can use 75 gr. bullets already.
Once in a while you need to bite the bullet, start from the scratch and build something from the ground up. Something that looks in the future, not something that brings over half the shortcomings of the old design.
Every attempt to get the "next combat cartridge" was wasted by the same AR15 mag/magwell. Both, 6.5 Grendel and 6.8 Spc, are not everything they could have been, because they had to work in the small AR15 magwell.
.
Jaws, you are both right and wrong.
When we do go with a new platform then the selection of a new cartridge will be broader, but until then we are stuck within the limits at hand.
As for the military, they dont see it your way, I do, but no they dont. DOD has looked at the 6.8spc and decided against it mainly because of its poor velocity. The military likes/wants velocity. Some ammunition companies have tried to fix the 6.8 poor velocities by loading lighter bullets, yes it has increased its velocity but because of the diameter of the bullet its BC has gone to shyt. This is why I decided to go with a 6mm bullet, my ideal bullet would be 6.5mm if we had the option of a different platform. 6mm will produce good BC and velocity.
deadduck357
Member
thanks Mav
Maverick223
Member
Np, dd357.
deadduck357
Member
Also I think the 6.5Grendel will have you beat for LR trajectory...prove me wrong and the world will soon follow.
...and Welcome to THR!
MAV223, I must have miss this, you are correct, but the 6.5Grendel was designed of a benchrest cartridge, it uses a modified benchrest case. The military will not go with it.
deadduck357
Member
Bolts are easy to manufacture and cheap. Possible to just ream out a 5.56 bolt.
JASmith
Member
What has been shown to date is a largely intiutive comparative assessment. The focus in justification appears to have largely been on the aesthetic and emotional - e. g., "more than," "smaller than," etc. In spite of this, things look interesting.
My technical side begs for numbers, e. g. "grains of water" compared with the alternatives, trajectory estimates, etc.
Moving to path forward:
The current acquisition standard is "capabiliites based," meaning that the new thing MUST fill an identified gap in military capabilities. The gap needs to be documented and justified.
An eternally frustrating part of capabilities based analyses that is demonstrating that the the gap can't be overcome by changes in tactics or other work-arounds.
So: Questions to be thinking about, but not necessarily posting are:
1. What capability gaps exist in infantry weapons that aren't already covered?
2. Can the proposed alternative fill in the gap at lower cost than the alternative or existing workarounds? (e. g., more liberal use of artillery, air-strikes, TOW, etc.)
I have nothing new to add except to address the thought that the 6mm is not enough bigger than the 5.56 to make a real difference in terms of terminal balistics. In reality there is a huge difference between the 22's and 24's in terminal balistics, and at not that much more of a weight. Here you have an effort to come up with a cartridge that is clearly better than the one in use now, which could be retrofitted into existing rifles with minimal cost. You can see it now in the middle east, M4 carbine equipped infantry are utilizing 77gr MK262 Mod1 ammo, hence the 1/7 twist but the velocity of this round is slow. The 5.56X45 case was never designed with that long of a bullet in mind. If you want to run it you should have a new case! Here you have the closest thing to a solution I have read yet.
Maverick223
Member
I don't think the military really cares about the historical lineage of the cartridge...they use a varmint cartridge right now (not to suggest it is ineffective).
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