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A better infantry round?

Discussion in 'Rifle Country' started by Scott Evans, Mar 22, 2003.

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  1. Scott Evans

    Scott Evans Moderator Emeritus

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    Just thinking out-loud … (day dreaming) … :eek:

    I am looking for a better infantry round. The attached drawing is two versions of a round that I think is missing.

    To me an infantry round should be as small as possible in the case and bullet dimensions without unduly sacrificing power at combat distance. (I think the 5.56 gives up too much) As I view the world combat distance is 0-500 meters. I know some think 300 is a max however, I want more particularly in areas like Afghanistan or Iraq.

    For the projectile I’m going with a .260†diameter slug weighing in some where between 100 & 130 grains.

    The max case diameter is 0.3850†(this enables tight stacking in magazines)

    I am looking at the two lengths as I want to be sure to achieve 2800-3000 fps from a 20†barrel and I’m not sure I can get enough propellant into the shorter case to do that. Also, my thinking here is that it is more important to keep the case diameter small then the overall length short.

    Thoughts?
     

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  2. JShirley

    JShirley Administrator Staff Member

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    Scott,

    I've been yearning for a new "all-purpose" (ha!) military round for a while. If you get sectional density high enough, you can have a small round that will penetrate as well and carry as far as a .308, while still being appreciably smaller and more controllable on full auto. One could replace all 249's, 240's, and M16 family weapons with a single new SAW and rifle series.

    I personally think the desired caliber is about 6mm, weight about 100 grains, with a muzzle velocity of about 3000 fps. I'm wondering what the ballistics of the new .243 WSSM will be...might fit the bill.
     
  3. Scott Evans

    Scott Evans Moderator Emeritus

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    JShirley,
    The .243 Winchester has a case diameter of .437 as compared to the .385†on mine.

    The larger case of the .243 W will reduce the amount you can stuff in a reasonable length magazine as well as the number that you can ultimately lug around on your person. I do however; like the performance of that round far better then the .223 for hunting 2 legers.

    I’m trying to find something with the “package size†advantages or the .223 round with real hitting power … even at distance.

    I saw someone mention the .257 Kimber but I’m unfamiliar with the stats on that round.
     
  4. RON in PA

    RON in PA Member

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    Always thought that the 250 Savage would make the ideal infantry round.
     
  5. Jeff White

    Jeff White Moderator Staff Member

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    It's already here...

    6.8x43...all that remains to be seen is if we can afford to re-equip the force. Which I just don't see happening. SOF, yes...the big Army, probably not.

    Jeff
     
  6. Scott Evans

    Scott Evans Moderator Emeritus

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    What are the specs on the 6.8 x43 ?
     
  7. Badger Arms

    Badger Arms Member

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    I've always thought the same thing. If it had been adopted instead of the 30-06 as an automatic rifle round, we might have had a working semi-automatic rifle about 10 years earlier than we ended up with having one. We would not have had to replace the 30-06 TWICE like we ended up doing.

    The 250 Savage has the same rim as the .308 but is 3/10ths of an inch shorter. It also has a greater taper which helps with reliability. One thing that I think makes the 250 Savage the right choice is that it operates at a lower pressure than the 30 calibers. Pumping up the pressure would provide an additional 1-200 fps.
     
  8. Chris Rhines

    Chris Rhines Member

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    Where was it, where was it... Ah-hah!

    Copied from TFL - The 6.5mm Christopher II

    Let's try something here.

    5.56mm NATO
    Case Length = 1.760"
    Case Head Diameter = 0.378"

    Nominal Bullet Weight = 55 grn.
    Nominal Velocity = 3240 fps*
    Nominal Muzzle Energy = 1282 ft-lbs.*

    * - Assume 20" barrel

    7.62mm NATO
    Case Length = 2.015"
    Case Head Diameter = 0.473"

    Nominal Bullet Weight = 150 grn.
    Nominal Velocity = 2820 fps*
    Nominal Muzzle Energy = 2648 ft-lbs.*

    Theoretical Cartridge - The 6.5mm Christopher II

    This will be, physically, exactly between the 5.56mm and 7.62mm cases.

    Case Length = 1.890"
    Case Head Diameter = 0.425"

    We're looking for performance between the 5.56mm and 7.62mm too, so let's theorize...

    Ideal Bullet Weight = 102.5 grn.
    Ideal MV = 3030 fps.
    Ideal ME = 1965 fpe, but higher is better. I'd like to be able to deliver 1000fpe out to 500 yards with this cartridge.

    Okay, let's see if such performance is even possible in the given case size. I found this on the AmmoGuide Server, it's a .30-30 case necked down to 6mm.

    6mm/30-30
    Case Length = 2.040" Close. The neck on this thing is looooong.
    Case Body Diameter = 0.422" Closer!
    Nominal Bullet Weight = 90 grn. We may have something here, neh?
    Nominal MV = 3000 fps. Oh, yeah!

    The .30 Remington also delivers similar performance, scaled to a much heavier bullet, and in a factory load.

    So, the cartridge can be done. Let's see what it will do upon leaving the barrel.

    Bullet - I'd take the Sierra .264" 107 grn. MatchKing HPBT. BC at ~3000fps is 0.420, which is very good. The 120 grn. MatchKing isn't quite as good, the 140 grn. is a bit better but too heavy for the case. We'll get to that later.

    Ballistics - 107 grn bullet at 3000 fps MV. Sight height of 1.0".
    0 yds / 3002 fps / 2142 fpe / -1.0"
    100 yds / 2772 fps / 1824 fpe / 0.0"
    200 yds / 2549 fps / 1546 fpe / -3.5"
    300 yds / 2339 fps / 1302 fpe / -12.2"
    400 yds / 2142 fps / 1090 fpe / -27.5"
    500 yds / 1955 fps / 909 fpe / -50.4"
    MPBR(10") = 353 yards with 300 yard zero.

    That's pretty good performance for a midsize case. In particular, the 107 grn. HPBT retains a lot of velocity (hence, more energy and better expansion/terminal performance) at longer ranges.


    - Chris
     
  9. Brian Williams

    Brian Williams Moderator Emeritus

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    here is a thread from thefiring line similar topic

    http://www.thefiringline.com/forums/showthread.php?s=&threadid=128662&highlight=6mm+SAW

    http://www.thefiringline.com/forums/showthread.php?s=&threadid=70695

    Another informative article,
    http://www.quarry.nildram.co.uk/Assault.htm

    copied from the Kernel on The firing line
    "...the best cartridge that never was."

    The US Army has already spent the better part of a decade, thousands of man-hours, and millions of dollars developing a 6mm cartridge - arguably the ultimate small arm cartridge. It's sitting on the self ready to go but will probably never be adopted because of political and economic reasons. It's not the biggest, the fastest, or a magnum anything. It's a compromise of size, shape, weight, function, recoil, and energy. Perhaps the perfect compromise.

    It's called the 6mm SAW - "the best cartridge that never was". It was developed in the early 70's and is officially known as the XM732 BALL. It was intended to be used with the (then experimental) Squad Automatic Weapon. SMALL ARMS OF THE WORLD, 12th Edition, by Ezell mentions the 6mm SAW briefly as it covers the development of the SAW machinegun in some detail.

    The 6mm SAW was not derived from 5.56x45 or the 7.62x51 (or any other cartridge case for that matter), it's case dimensions are totally unique. According to CARTRIDGES OF THE WORLD, 8th Edition, by Barnes the OAL of a loaded round was 2.580". The case had a .410" head dia. and was 1.779" long. It was loaded with an extremely streamlined 105 gr bullet that moved out at 2520 fps from an 18" barrel, not that far behind cartridges like the .243 Winchester and 6mm Remington.

    It wasn't just a pie-in-the-sky project. Development got pretty far, a lot of ammunition was even loaded in bulk at military arsenals. You might even turn one up at a big gun show if you scrounge around the cartridge collectors' tables. $5 a round last time I saw one.

    One interesting facts about the 6mm SAW is it was the first cartridge to be designed by computer. The technique called "parametric design" was a complicated model of complex thermodynamic equations. The Army wasn't that impressed and once they figured out how to make tracers work in .223 caliber bullets they dropped the 6mm SAW. To bad in my opinion, the 6mm SAW had a lot going for it, and in civilian form the brass would have been the basis for many, many interesting cartridges that never will be.

    Excerpt from Guns Review International, February 1996 by Anthony Williams

    "....... in a series of experiments conducted by British, American and (possibly) Russian agencies to discover the ideal military small arms calibre. In the late 1960s, the Royal Small Arms Factory at Enfield began a detailed theoretical analysis of the striking energy needed to disable soldiers with various levels of protection, and the ballistics required to deliver that energy at battle ranges for a number of different calibres. The conclusion was that the optimum calibre would lie between 6mm and 6.5mm, and an experimental 6.25mm cartridge (based on the abortive 7mm round) was developed which was claimed to have significant advantages over both the 5.56mm and 7.62mm calibres. Performance proved to be virtually equal to the 7.62mm at up to 600 metres, with recoil and ammunition weight much closer to those of the 5.56mm.

    At the same time, the US Army realised the need for a light machine gun with a longer effective range (out to 800 metres) than the 5.56mm cartridge could provide but appreciably less weight than the 7.62mm M60 MG. Their research led to the development of the 6mm SAW (Squad Automatic Weapon) cartridge. A relatively heavy bullet combined with a moderate velocity were selected for the optimum long-range performance. In the event, weapons firing improved 5.56mm ammunition were selected instead, largely to avoid the supply problems created by the use of three small-arms calibres. More recently, it has emerged that Russian armament firms, who had earlier copied NATO in producing a small-calibre (5.45mm) cartridge, are now offering weapons in a new 6mm calibre."

    -- Kernel


    __________________
     
  10. JohnKSa

    JohnKSa Member

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    Hmmm.

    In terms of ballistics, it sounds like the Swedes got it right over 100 years ago.

    6.5x55mm

    140 grain .264" bullet @ 2600fps.

    Of course, the cases were bigger & longer than they would have to be today with the new improved powder technology.
     
  11. Jim Watson

    Jim Watson Member

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    These discussions always remind me of the article by Col Frank T. Chamberlain in P.O. Ackley's Handbook for Shooters and Reloaders. He was a medical officer on hand for trials of ammo for the forthcoming semiautomatic infantry rifle in the 1930s, and did the autopsies of pigs and goats shot with various rounds. He said there was a .256 (Old term of bore diameter of a 6.5mm) with 125 grain flatbase at 2700 fps that was the most destructive round tried. With a cartridge weight half of the .30-06 and better ballistics than the .276 Pedersen it would still make sense now.

    I have never seen it mentioned anywhere else and do not know what it was derived from or was most similar to.

    On the other hand, the two true combatant countries that entered WW II with smallbores, Italy and Japan with their own 6.5s, concluded in Ethiopia and China that they needed more gun and went up to the .30 cal range with 7.35 Italian and 7.7 Jap. Neither could make the changeover in wartime, Italy actually backtracked and rebarreled a lot of Carcanos to 6.5 and Japan used both calibers of Arisaka. I wonder if they might have done better to have cut bullet weight and increased velocity in the 6.5s. But nobody then was willing to cut 6.5 bullet weight below 139 grains, and nobody listened to Chamberlain.
     
  12. Sarge111

    Sarge111 member

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    Here we go again...

    re-inventing the wheel.

    I think the 7.63x51 was the answer, and that firearms technology and design could have solved the problem of rifle weight to an appreciable degree. Instead, we wound up with the 5.56; I see this as an either/or issue, but then I tend to think in absolutes and that kind of thinking is no longer fashionable.

    For those who want something in between, then 7-08 is a close to perfection as anyone could ever hope for. But like anything else the federal gubmit gets involved in, an easy answer right under their noses will get buried in the bureaucratic red tape and comittee-forming that always accompanies the quest for answers- usually to questions that either don't exist, or were answered a long time ago.

    The post-Miami search for the perfect LE handgun round is a prime example of what generally results from this process. The initial result was the 10mm, which actually looked like it might do some things that autopistol rounds haven't accomplished before. Then "evil recoil" reared its ugly head, which in the end resulted in the birth of the .40 S&W. This is not a bad round, but it won't do anything that a standard-pressure .45/185 accomplishes, except make a smaller hole. Oh yes, I forgot that 14 of them will fit in a service pistol- great. In order to accomplish this, we made the .40 operate at about twice the pressure of the .45 ACP. Not so great. Now we carry 14-shot service autos, and don't shoot them nearly as well as we did our .357 revolvers.

    I guess the quest for new & better weapons will go on as long as there is human coinflict, and there are occasionally some benefits from all the research that gets done in the process. One thing remains constant however, and that is the fact that you have to shoot well to make anything effective in combat. I have to wonder if that isn't the real answer to "the problem".
     
  13. Andrew Wyatt

    Andrew Wyatt Member

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    I like .308 as much as the next guy, but it's nice to not have a rifle that doesn't weigh 12 pounds, loaded.
     
  14. BigG

    BigG Member

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    Shoot, Andrew, the way they keep piggin up the M16, it will soon weigh 12 lbs loaded.
     
  15. Brian Williams

    Brian Williams Moderator Emeritus

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    this attached pic has a copy of the line up of russian and us rounds along with a 6mmSAW
     

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  16. Zorro

    Zorro Member

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    It has a name.

    6MM PPC!
     
  17. Bostonterrier97

    Bostonterrier97 Member

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    There are a number of good rounds...
    6.5x55mm Swedish Military Round
    257 Roberts and 257 Roberts Ackerly Improved
    25-06
    243 (invented by Warren Page)
    260 Remington
     
  18. Badger Arms

    Badger Arms Member

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    It seems we are all forgetting controllable automatic fire as a requirement for an infantry round. I'm sorry, the 25-06 would be uncontrollable. I think that the 250 Savage would be marginal. Perhaps a 6mm-250 or, hmmmmm, the 6mm PPC.
     
  19. Bostonterrier97

    Bostonterrier97 Member

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    "Controllable" Automatic Fire.....this is true..but..the US has moved away from having Assault Rifles which are fully Automatic. The M16A2 now only comes in 2 flavors: 3 round Burst and Semi Auto. The Canucks varient of the M16 has Full Auto Capability.

    It was found that even when shooting the lighter 55 grain M193 Ammunition, in a rifle with an inline stock in full Auto, it was still largely uncontrollable. After the second round has been fired, usually most of the other rounds would miss the target.

    So we are back to Semi-Auto....and the need for firing heavier, more powerful bullets is necessary for desert warfare and for penetration issues.

    So..I think the 257 Roberts, or 260 Remington would make a very good infantry round.

    The 257 Roberts Ackerly Improved has almost as much power as the 25-06, but has a shorter case.

    Perhaps the US really should move away from having ONE infantry rifle, and go back to having a mix of different infantry rifles chambered in different calibers. This would give our platoons greater flexibility in terms of firepower and penetration.
    This is how it was during WWII and Korea, when it was common to find a platoon armed with weapons chambered in 30-06 (the Garand, and BAR), 30 Carbine (the M1 and later the M2 Carbine) and the Thompson Machine (45 ACP).

    In spite of this mix of ammunition troops engaged in long range and protracted engagements such as happened to Merrill's Marauders or what happened to the Marines at Chosin Reservoir, Korea, had no trouble being supplied with enough ammunition. And this was in spite of the primitive means of logistical support.

    The arguement of the necessity of having only ONE service cartridge due to the danger of running out of Ammunition, no longer makes much sense due to the improvement in the ability of our logistical capabilities in supplying our troops.

    As for Special Forces: team members are allowed to choose what types of weapons and ammo they carry anyway. Some carry AK's, others HK's, and others M16's. A few even carry the M14. If they run out of Ammunition, Supplies are dropped plane or helicoptor.

    Most of our troops are transported and supplied through either Helicoptors or Mechanized Ground Transport. The Days of Pack Mules hauling Munitions to the Front line is long gone.
     
  20. Scott Evans

    Scott Evans Moderator Emeritus

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    That makes great sense to me. Reduce the number of M-16’s by half and replace them with M-14’s. W already use the 7.62 for the Gulf 240.
     
  21. No4Mk1*

    No4Mk1* Member

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    I would say leave it as is or use only 7.62mm. The advantage of weight is present if troops use 5.56mm. The advantage of commonality with GPMGs is present if they use 7.62mm. A hybrid round loses some of the weight advantage while still not being able to share with vehicle mounted 7.62mm MGs. Reducing the size of the vehicle mounted GPMG would be the worst decision as weight doesn't matter as much for vehicles.

    7.62x51mm is a small and compact round as far as I am concerned. I think the fact that any vehicle with a 7.62mm MG could resupply many troops in the field is enough of a reason for all use 7.62mm. If the troops ran low on rifle ammo but happened upon a M1 Abrams they could take a few thousand rounds from the M1's 7.62mm supply.
     
  22. Glock Glockler

    Glock Glockler Member

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    The 6.5mm is utterly luscious with it's ballistic coefficient, so I would christen the 6.5 Glockler by using a 7.62 x 39 Russian case necked down to a 120gr 6.5mm pill, or we could use a Czech 7.62 x 45 case necked down to a 6.5mm.

    Throw in some modern bullet design and a new rifle, and you have an absolutely lethal mix ready to go.
     
  23. Marko Kloos

    Marko Kloos Moderator Emeritus

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    Yeah, but your case diameter is still up there, so you don't really gain any space advantages. Might as well use a .243, if you want to go with a case that wide at the base. Also, the 7.62x39 has some fierce case taper to it, so they won't stack real neat.

    Anybody ever resize the 5.56x45 case mouth a la .300 Whisper, only for a 6-6.5mm bullet? That .300 Whisper has some good long-range punch, and the bullets have beaucoup sectional density. Wonder what that concept would yield with a 6mm bullet at 90 grains, or a 6.5mm at 110-120 grains?
     
  24. cratz2

    cratz2 Member

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    6x45 and 6x47. Based on the 223 and 222 Magnum cases, respectively. I think you can get the 6x47 up to nearly 2,900 fps or so with a 75 gr bullet. Not sure about the ability of a 6.5 based on the 5.56 cartridge. I think you'd be having some pretty low velocities and poor 200-300 meter performance.

    Their biggest drawback in civilian hands is lack of long range energy but if the M16 is only a capable of 300 Meter aimed fire, they're plenty effective at that distance. They would obviously work in the M16/M4 platform and have very similar recoil to the 5.56. The 14.5" barrels would be a detriment so maybe we could go with 18" barrels. Less velocity so barrels would last longer and could be slightly thinner to help offset the weight.

    Most folks that use them seem to use them in Contenders and Encores but I know at least one person on this board has an upper. I keep saying I'm going to buy one or build one, but I guess it's just not that pressing right now.

    Someday... Right after I built my 6.5x284 or 6.5-06. I suppose. ;)
     
  25. Glock Glockler

    Glock Glockler Member

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    Lendringser,

    The advantage of the Russian case would be shortness of it compared to the 5.56, which would allow for a shorter action and cycling, as well as more efficient burn capacity. That would be in addition to it's greater case capacity.

    The .243 Winchester has some groovy ballistics but it is only a 308 case necked down, so we'd not be saving much in the way of OAL, and although I'm as American as they come, worshipping more and more power, that round might have a wee bit too much for an assault rifle caliber.
     
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