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Author Topic: New Army Rifle caliber...  (Read 4385 times)

Langenator

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Re: New Army Rifle caliber...
« Reply #25 on: May 19, 2017, 08:59:21 AM »
I've suggested before, use the old Czech 7.62x45 cartridge as a starting point, neck it down to 6.5mm somewhere in the 120-140 gr range, and fiddle to find the best combination of primer, powder, projectile, and barrel.
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    Adskii

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    Re: New Army Rifle caliber...
    « Reply #26 on: May 19, 2017, 09:40:55 AM »
    Why go with the lesser of Soviet rounds? Use the 7.62 x 54.

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    Re: New Army Rifle caliber...
    « Reply #27 on: May 19, 2017, 12:02:51 PM »
    They want to extend effective range and keep recoil to a minimum?  AR-10 in .243 Winchester.  20" barrel, flat top and free floated.  Ambidextrous safety.

    It would allow the use of 90%+ of the accessories that are currently used on the M-16/M4 platform, and the 5.56 M4s could be retained for basic training and stateside Reserve/Guard units and security forces.
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    Re: New Army Rifle caliber...
    « Reply #28 on: May 19, 2017, 01:09:34 PM »
    They want to extend effective range and keep recoil to a minimum?  AR-10 in .243 Winchester.  20" barrel, flat top and free floated.  Ambidextrous safety.

    It would allow the use of 90%+ of the accessories that are currently used on the M-16/M4 platform, and the 5.56 M4s could be retained for basic training and stateside Reserve/Guard units and security forces.

    But that s___ makes too much sense for .gov  ::) .
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    Re: New Army Rifle caliber...
    « Reply #29 on: May 19, 2017, 03:25:51 PM »
    Why go with the lesser of Soviet rounds? Use the 7.62 x 54.

    They want bigger than 5.56 and smaller than 7.62.  Also, the 7.62x54R is between the .308 and .30-06 for size, and they probably (didn't read the whole article) want something smaller than those to allow the soldier to carry more rounds.

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    Re: New Army Rifle caliber...
    « Reply #30 on: May 19, 2017, 04:23:46 PM »
    So the Military is playing with .260 Remington now, in a SCAR rifle.  Which is actually pretty dang good.  I like that.  It's essentially a 6.5 Creedmore that uses existing magazines.    That would be an interesting option.
    However, our Ground Pounders are using more Suppressors, and are liking them.  So something that can work with and without a Can is probably a strong option.  .300BLK might be a good round... Or maybe going back to the 6.8SPC concept, with a fast load and heavy sub-sonic load.
    But overall, this is getting very interesting.
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    Re: New Army Rifle caliber...
    « Reply #31 on: May 19, 2017, 06:00:58 PM »
    So the Military is playing with .260 Remington now, in a SCAR rifle.  Which is actually pretty dang good.  I like that.  It's essentially a 6.5 Creedmore that uses existing magazines.    That would be an interesting option.
    However, our Ground Pounders are using more Suppressors, and are liking them.  So something that can work with and without a Can is probably a strong option.  .300BLK might be a good round... Or maybe going back to the 6.8SPC concept, with a fast load and heavy sub-sonic load.
    But overall, this is getting very interesting.

    A 6.5mm round in something like an AR-10 would be damn hard to beat for an all around cartridge. 6.5 Creedmoor already functions in existing 308 mags so there would really be no reason for not going with it over something like the 260.

    I assume the military will just waffle about again with tests and then say it is not enough of an improvement to switch.
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    Re: New Army Rifle caliber...
    « Reply #32 on: May 19, 2017, 10:31:36 PM »
    260 Remington loads up fine in my Magpul SR-25 mags too.
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    Re: New Army Rifle caliber...
    « Reply #33 on: May 24, 2017, 03:50:04 AM »
    I only know from what little I read that the pressure spike ruptured chambers OR fractured the projectile and gassed out that way. Some was caused by simple over pressure of the materials and others failures were caused by exceeding the speed of sound in some material causing critical failures.
    Right, which is why part of my query regarded use of newer metallurgy and materials as well as different chamber and breech designs.   If what you're saying is that current standard design firearms can't deal with much higher pressures I agree. There's a very good reason for max pressure loads being listed in reloading tables.   
    I'm just wondering if any new advances in materials technology has given us something we can use to construct a chamber that could deal with higher pressures.  It's idle curiosity on my part.  I like the new railguns, and as a former tanker I expect to see them on tanks (assuming tanks aren't rendered obsolete by drones and other advancements) within the net 10-20 years.   The problem with them for individual weapons is the power supply, an issue I don't see being solved for quite a long time.  Hence curiosity about what may or may not being explored to create a more efficient chemical propellant for projectiles.[/quote]

    You cannot push a projectile down a bore faster than the speed of sound in the gas in the bore. This is one of the reasons light gas guns are used in scientific tests. They use a different gas with a higher speed of sound to achieve higher velocity. https://en.wikipedia.org/wiki/Light-gas_gun     
    And yet we fired 120mm main gun rounds that have muzzle velocities well over that.   
    I read your cite , I'm just at a loss as to how to reconcile that information with the speed of the rounds we fired (and I g**gled them just to be sure my memory wasn't playing tricks on me).   

    I also know that the pressure spikes were not predictable. A slight increase in temp or charge might make the runaway pressure spike. As pressure goes up so does heat. So you have a double hit on the materials of needing to be taking more pressure AT higher temperatures. I know the high temperatures of the metal type propellants cause insane levels of wear on the bore. Some erosion being so great as to make it no longer functional after one shot.   

    I am by no means an expert on any of this stuff. I just know what I have read from pure curiosity.
    I wonder if a ceramic bore sleeve in an alloy barrel would fare better? 

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    Re: New Army Rifle caliber...
    « Reply #34 on: May 24, 2017, 03:03:16 PM »
    Quick reply on why we have very high velocity rounds coming out of the barrel when the pressure wave can only travel at the speed of sound.  The speed of sound is directly proportional to the temperature of the gas.
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    Re: New Army Rifle caliber...
    « Reply #35 on: May 24, 2017, 03:24:46 PM »
    Right, which is why part of my query regarded use of newer metallurgy and materials as well as different chamber and breech designs.   If what you're saying is that current standard design firearms can't deal with much higher pressures I agree. There's a very good reason for max pressure loads being listed in reloading tables.   
    I'm just wondering if any new advances in materials technology has given us something we can use to construct a chamber that could deal with higher pressures.  It's idle curiosity on my part.  I like the new railguns, and as a former tanker I expect to see them on tanks (assuming tanks aren't rendered obsolete by drones and other advancements) within the net 10-20 years.   The problem with them for individual weapons is the power supply, an issue I don't see being solved for quite a long time.  Hence curiosity about what may or may not being explored to create a more efficient chemical propellant for projectiles.
    And yet we fired 120mm main gun rounds that have muzzle velocities well over that.   
    I read your cite , I'm just at a loss as to how to reconcile that information with the speed of the rounds we fired (and I g**gled them just to be sure my memory wasn't playing tricks on me).   

    You fired 120 mm tank rounds over what speed? All the info I can find is around 5000 to 6000 fps. Which is well within the speed of sound for the gas in the barrel. I believe the speed of sound in a modern firearms barrel while firing is around 7000 fps.

    The light gas gun cite has velocities listed in km/s. So you are likely confusing km/s for fps. The lowest listed speed for the light gas guns there is 6km/s. Which is in the neighborhood of 19000 fps. Which would produce a recoil energy able to lift 2+ M1 Abrams tanks firing the older APFSDS rounds out the 120mm.

    The main issue with trying to compare tank cannons to infantry rifles is scale. If you scaled the Abrams cannon down to 308 bore. It would weigh around 1300 pounds. Which is a bit on the heavy side for most folks to carry.

    Cannons also get the added benefit of the area of bore effect for basically more force applied to the projectile for the same pressure. As simple math tells us that twice the bore increases the bore area by 4 times. The pressure advantage can even be leveraged more by going with low density projectiles OR if you wish to maintain density sabot shot of some sort or another. Cannons also get the benefit of projectile dwell time while under pressure. As the barrel lengths are not ratio dependent for speed. It is just a flat time increase for the longer bore of the cannon. You also get the square-cube law to help the cannon with not running out of propellant gas in the long bore.

    The main issue with the tested new propellants is they spike to pressures in the hundreds of thousands of PSI not just a few thousand more than we have with modern gunpowder. So a simple material change is not gonna cut it. 

    The metal based propellants wear through the ceramic nozzles on booster rockets in only one burn. Some are producing temps up over 10k degrees. They are just too hot and way too abrasive. You can imagine something akin to a very high pressure sandblaster shooting burning thermite to get an idea of the conditions.     
    « Last Edit: May 24, 2017, 03:43:09 PM by Plebian »
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    Re: New Army Rifle caliber...
    « Reply #36 on: May 24, 2017, 03:40:48 PM »
    The other main issue Lowkey is you are just barking up the wrong tree to reduce overall loaded round weight. The projectile and case are by far the main contributors to weight of a loaded cartridge. We already reduced the weight of the projectile significantly when we went from 7.62 to 5.56. The smaller case + projectile also added to massive savings on weight of loaded rounds.

    The charge weight of powder is just not that significant to overall round weight. If you take a pretty crazy charge of powder for 5.56. Lets say we take 28 grains. We now use a propellant that just uses 7 grains(4 times more energy density). You have only lost 21 grains of total cartridge weight. YOUR projectile weighs 55 grains at least. Lets also go full hog and say we can reduce the case weight by half. 95 grain brass case to 47 grain case. You have now saved a grand total of 68 grains from a total loaded round. There can almost be that variance in just bullet weight from lightest to heaviest. If you need to add any weight to the rifle to take the higher pressures. You have eaten all your weight savings. 
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    Re: New Army Rifle caliber...
    « Reply #37 on: May 24, 2017, 05:57:27 PM »
    Which brings us the long way 'round back to the 6mm x 45, or the current 5.56mm necked up to take a 6mm bullet.  Incrementally better but better all the same and it can be used in existing equipment with only a barrel change.  It can also be loaded on current automated loading equipment with only a change in loading dies and a recalibration of the charge weight.  I think the 6mm bullet in the current weapons platform makes it a legitimate 500 yard round in terms of lethality.   :hmm
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    Re: New Army Rifle caliber...
    « Reply #38 on: May 24, 2017, 10:47:39 PM »
    I'm guessing 300 BLK doesn't have the legs, eh?

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    Re: New Army Rifle caliber...
    « Reply #39 on: May 24, 2017, 11:45:36 PM »
    Its a very good specialized cartridge.  Suppressed its hard to beat in a CQB scenario with the heavy bullet loads.  I think it falls short in the long range role though.  Its intended use is really inside of three hundred yards.   The loaded ammunition weighs significantly more per round than the current ammo and switching to that round would likely require a substantially different tactical doctrine than is currently in use.   :hmm

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    Re: New Army Rifle caliber...
    « Reply #40 on: May 25, 2017, 08:25:53 AM »
    The other main issue Lowkey is you are just barking up the wrong tree to reduce overall loaded round weight. The projectile and case are by far the main contributors to weight of a loaded cartridge.
    I wasn't suggesting it's the only way to reduce the weight. 
    There's a new small arms case that I'm following with some interest. 
    A nickel alloy case with an aluminum base plate at half the weight of a brass case, and I'm pretty sure many of you are following it as well. 

    I don't see reducing projectile weight within a caliber as beneficial unless the projectile is going to use a mechanism along the line of being explosive or a fast acting toxin, which isn't something I see happening. 
    Someone out there made some 9mm projectiles out of aluminum a few years back and tried marketing them as SD rounds while touting the high velocity the rounds achieved, and IIRC they didn't work out too well in the real world. 
    Muzzle velocity is good, but you need sufficient mass to retain it and sectional density for penetration. 

    Same old argument, mass vs velocity. Small fast projectile vs large slow projectile.   

    So if we can not:
    - Raise any projectiles velocity above a certain maximum speed, which precludes the idea of a hypersonic BB  ;)
    - Substantially reduce the weight of projectiles which depend on their mass to retain sufficient velocity to remain effective(SD, BC, et al).

    If we can't make effective projectiles much lighter, and we can't make effective projectiles move faster with chemical propellants, then reducing case weight and the propellant weight used to meet existing velocities would seem to be the only avenues available to reduce cartridge weight.   

    Out of the two case weight is higher, but I was already aware that ways to reduce it were being explored.
    Propellant weight may be a much smaller factor, but due to economy of scale it does add up.   

    If I'm substantially wrong about this I'd really like to know.  Not being sarcastic here.



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    Re: New Army Rifle caliber...
    « Reply #41 on: May 25, 2017, 09:48:16 AM »
    You fired 120 mm tank rounds over what speed?

    Well over the speed of sound.

    Speed of sound                       1,125 ft/s
    120mm Sabot Muzzle Velocity  5,500 ft/s.

    My apologies for not making it clear that I wasn't referring to the light gas gun, but no one firing projectiles in combat is going to be doing so with a bore filled with helium or hydrogen.

    The main issue with trying to compare tank cannons to infantry rifles is scale. If you scaled the Abrams cannon down to 308 bore. It would weigh around 1300 pounds. Which is a bit on the heavy side for most folks to carry.

    Please take this in the most lighthearted way possible, but  :banghead.
    This is why my initial question specifically mentioned improvements in materials technology. I'm well aware that the alloy for the main gun breech block is very heavy, I've dropped breech blocks more than a few hundred times and it requires a chain hoist.    I had hopes that 25 plus years after the design of the 120mm main gun breech block currently in use that in the age of high strength industrial ceramics, carbon fiber materials, nano tubes, and other assorted leaps forward in making stronger lighter materials that someone had explored using something of that sort to make a chamber that can handle much higher chamber pressures and pressure curves. Similar in how moving from iron to steel allowed higher chamber pressures in cannon.



    The main issue with the tested new propellants is they spike to pressures in the hundreds of thousands of PSI not just a few thousand more than we have with modern gunpowder. So a simple material change is not gonna cut it. 

    I wasn't assuming someone would be restricted to  simply machining a chamber in a different material that was identical to a steel/current production chamber in all other aspects. 



    The metal based propellants wear through the ceramic nozzles on booster rockets in only one burn. Some are producing temps up over 10k degrees. They are just too hot and way too abrasive. You can imagine something akin to a very high pressure sandblaster shooting burning thermite to get an idea of the conditions.     
    Is this the only new type of propellant under development?


    If the answer is yes or that other such research as so far run into dead ends all well and good.
    What I find a bit odd is the apparent declaration that it's somehow a scientific impossibility to come up with a projectile weapon using a more efficient (power to weight) chemical propellant, or put more simply, "Can we reduce the overall size and weight of a cartridge for a given sized projectile without loosing performance?"   
         
    "Not yet", sure.  "Impossible", that I don't buy. 



    Plebian

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    Re: New Army Rifle caliber...
    « Reply #42 on: May 25, 2017, 12:09:25 PM »

    Well over the speed of sound.

    Speed of sound                       1,125 ft/s
    120mm Sabot Muzzle Velocity  5,500 ft/s.

    My apologies for not making it clear that I wasn't referring to the light gas gun, but no one firing projectiles in combat is going to be doing so with a bore filled with helium or hydrogen.
     
    Please take this in the most lighthearted way possible, but  :banghead.
    This is why my initial question specifically mentioned improvements in materials technology. I'm well aware that the alloy for the main gun breech block is very heavy, I've dropped breech blocks more than a few hundred times and it requires a chain hoist.    I had hopes that 25 plus years after the design of the 120mm main gun breech block currently in use that in the age of high strength industrial ceramics, carbon fiber materials, nano tubes, and other assorted leaps forward in making stronger lighter materials that someone had explored using something of that sort to make a chamber that can handle much higher chamber pressures and pressure curves. Similar in how moving from iron to steel allowed higher chamber pressures in cannon.


     
    I wasn't assuming someone would be restricted to  simply machining a chamber in a different material that was identical to a steel/current production chamber in all other aspects. 


    Is this the only new type of propellant under development?


    If the answer is yes or that other such research as so far run into dead ends all well and good.
    What I find a bit odd is the apparent declaration that it's somehow a scientific impossibility to come up with a projectile weapon using a more efficient (power to weight) chemical propellant, or put more simply, "Can we reduce the overall size and weight of a cartridge for a given sized projectile without loosing performance?"   
         
    "Not yet", sure.  "Impossible", that I don't buy.

    Ah. You didn't realize that the speed of sound of the heated gas in the barrel was much higher than atmospheric.

    The simple answer to chamber design and materials is not really. Steel is still king so to speak for taking shock load, heat transfer and wear resistance. We have many materials better in single properties, but the combo steel has, is tough to beat, so to speak. 

    Propellants/explosives have been researched to death. We are pretty sure no radically new nitrogen compounds are coming down the tracks. You would also likely not gain much power density either. Since modern gunpowder is a nitrogen compound. This has lead to more experimentation in metal based(using metal in the chemical sense here not the vernacular sense) compounds. Which have some awesome power densities, but are absolutely brutal in heat production and abrasion.

    Firearms are a very mature technology. Any time you get into very mature technology leap frogging is highly unlikely. Also the answer to any question with any intelligence is 'not yet'. There is never certainty in the future only solid educated guesses.

    That leaves us with the same old boring tweaking of components, projectile weight/size/bore diameter/material, barrel length, case construction.

    Which is why the military keeps waffling about trying to find new weapons, but will very likely not change until we move past chemically propelled projectiles.   
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    Re: New Army Rifle caliber...
    « Reply #43 on: May 25, 2017, 12:42:56 PM »
    Ah. You didn't realize that the speed of sound of the heated gas in the barrel was much higher than atmospheric.

    Actually I would have thought it would be less due to density.
    For example, doesn't sound travel faster in water than in air?

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    Re: New Army Rifle caliber...
    « Reply #44 on: May 25, 2017, 12:50:56 PM »

    That leaves us with the same old boring tweaking of components, projectile weight/size/bore diameter/material, barrel length, case construction.

    So in small arms design we're stuck until someone comes up with much more robust materials for constructing chambers and barrels and/or a more potent propellant that won't cause the weapon system to outgas it's own guts when fired or a major leap in battery technology that will create a power supply capable of supplying enough energy to fire hundreds of shots through a gauss rifle of about the same weight as a current assault rifle where said power supply weighs the same or less than the current load out of conventional ammunition.
    Or we say to hell with it and design and field reliable HE rounds for small arms. 

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    Re: New Army Rifle caliber...
    « Reply #45 on: May 25, 2017, 12:55:58 PM »
    You know what would really save troop lives? What would absolutely increase the American soldiers combat effectiveness in the field? Instead of .gov hem and hawing over which cartridge to use, why don't we work on the crummy ROE we impose on them and allow them to do their job  :coffee. I guarantee it would shorten the war and save lives.
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    Capacity wasn't really an issue then... and honestly really it's not even an issue now.
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    Re: New Army Rifle caliber...
    « Reply #46 on: May 25, 2017, 01:23:55 PM »
    You know what would really save troop lives? What would absolutely increase the American soldiers combat effectiveness in the field? Instead of .gov hem and hawing over which cartridge to use, why don't we work on the crummy ROE we impose on them and allow them to do their job  :coffee. I guarantee it would shorten the war and save lives.
    That would require politicians to identity the threat, state what results they required, and turn the rest over to the military to sort out without further meddling, micromanaging, or second guessing until the results are achieved by the professionals who know what the hell they're doing.  If you believe that's likely to happen anytime in the near future I have a bridge I'd like to sell you. Cash, small bills, with non-sequential serial numbers please.  ;)

    How it's done now is rather like realizing yo need a triple bypass, engaging the services of the best qualified surgeon out there, and then insisting on remaining awake during the procedure and telling him how to do it and overriding his judgment at nearly every turn, and then finally complaining that he did a piss poor job of removing your appendix.  :doh
     

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    Re: New Army Rifle caliber...
    « Reply #47 on: May 25, 2017, 02:08:40 PM »
    That would require politicians to identity the threat, state what results they required, and turn the rest over to the military to sort out without further meddling, micromanaging, or second guessing until the results are achieved by the professionals who know what the hell they're doing.  If you believe that's likely to happen anytime in the near future I have a bridge I'd like to sell you. Cash, small bills, with non-sequential serial numbers please.  ;)

    How it's done now is rather like realizing yo need a triple bypass, engaging the services of the best qualified surgeon out there, and then insisting on remaining awake during the procedure and telling him how to do it and overriding his judgment at nearly every turn, and then finally complaining that he did a piss poor job of removing your appendix.  :doh

    Believe me, sir. I fully realise that suggesting the government do something useful is nothing less than a futile effort  :neener.
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    Do we forget that cops were primarily still using 6 Shot Revolvers well through the mid 80's? It wasn't until after 1986 that most departments then relented and went to autos.
    Capacity wasn't really an issue then... and honestly really it's not even an issue now.
    Ray Chapman, used to say that the 125-grain Magnum load’s almost magical stopping power was the only reason to load .357 instead of .38 Special +P ammunition into a fighting revolver chambered for the Magnum round. I agree. - Massad Ayoob

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    Re: New Army Rifle caliber...
    « Reply #48 on: May 25, 2017, 02:41:38 PM »
    Actually I would have thought it would be less due to density.
    For example, doesn't sound travel faster in water than in air?

    Correct. It would not be less dense tho. There is a much higher PSI in the barrel than the atmosphere, or the gun doesn't work.

    Quick reply on why we have very high velocity rounds coming out of the barrel when the pressure wave can only travel at the speed of sound.  The speed of sound is directly proportional to the temperature of the gas.

    RetroGrouch has it down pat here.

    Heat is simply the measure of all the kinetic energy of the molecules in an object. You increase the heat. You increase the speed of sound because each molecule is traveling faster. So it hits other molecules in a more rapid(by time) fashion. That therefore increases the speed of transmission of the information(pressure wave).

    There is a ton of horribly icky math in gas laws/theories. So the above is just a simplified statement. 
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    Re: New Army Rifle caliber...
    « Reply #49 on: May 25, 2017, 02:48:50 PM »
    Correct. It would not be less dense tho. There is a much higher PSI in the barrel than the atmosphere, or the gun doesn't work.

      :doh:   :facepalm
    For some reason I was thinking of the air in the barrel ahead of the projectile, as in the resistance it would present to the projectile as the limiting factor you were speaking of,  rather than the expanding gases behind the projectile.

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