Gunzilla - explosive formed projectile, sounds a lot like the self-forming slug, Project Fire Ant.  Talk about footage that gives me the willies .... that little quad vaporizing the turret of a Soveit MBT.

Gogi - the propellant is only part of the noise, the sonic boom of the bullet adds a fair share ... not much to be done there, unless you go subsonic ....

PaDanby - the rotating HG, this may sound ignorant, but the Fulton Armory HG does this more-or-less, it has 4 rails and normally would be secured with a locking ring.  It would be simple enough to modify for ball detents that would allow just that quarter turn.  Also, you could make something that attaches to the flat top, drew up the CAD designs for that a year or two ago ....

Now, there was an interesting thought in GoGi's post.  SMALLER cases with hotter propellant.  Provided it would not destroy the rifle, a smaller charge of hotter propellant could impart the same energy to a projectile ... An interesting concept ....  BRASS cases may no longer work .. then again, the brass forms the pressure seal between bolt and chamber.

M

I said that first!

Really though, it sounds like a pretty good/simple idea. Keeping a zero might be hard, though.

I got to play around with some of this sort of stuff (back in the day)... We were able to get the projectile speed to the point that there was actually a problem with the steel projectile melting "in flight" -- Think of a solid steel shotgun slug doing 20,000 fps!

Aiming it was a bit of a chore however.

This is a good idea, something like it that I have seen used cases made using a steel case head with a brass case body -- the chamber pressures were out there like pluto. Down side for a MBR is that the projectile speed, matched to the relatively small bore diameter could not handle ANY sort of water incursion... no chance of evacuating the bore and it was discovered that the path of least resistance, often, was right out the side of the barrel! Sort of a downer to the operator.

Gunz

Man, you said a mouthfull there... Close Quarters takes on a whole new meaning shipboard! How about compartments that 2 people can not stand up in at the same time... and actually discharging a weapon in an all steel "closet" is an experience!

There is some thought going into this subject however.

What about non-lethal subsonic projectiles that can be fired with no conversions to the gun, to use inside ships?

Fill your paint ball loads with loose steel shot .... disintegrating bean bag loads ...

On the 4 rail, there are ways to secure it once rotated.  Like a modified ARMS 36EX.

Hey Gunz, aiming Fire Ant was pretty accurate, like being able to pick out a car parked between two others.  Optical recognition coupled with neural networks allowing free roaming, the true self-propelled gun.  Brass alloy plate approaching plasma state ....

On the HE propellant, I wasn't going to increase the projectile speed, I was going to decrease the overal cartridge size.  Like sticking a 168 gr HPBT-MK in a 32 ACP case but still getting 7.62 NATO performance.  Or sticking the 62 gr 223 on a 22 LR case and getting 3200 fps .... that's where the higher energy propellants might shine ...

OK< bed time

Marty

I'd really like a good reliable .45ACP carbine in an AR configuration that takes grease gun mags

 I think the AR - 15 needs to DIGRESS.  Let's go back to what the damn thing was designed to do:  light gun ala the XM-16E1
    light bullet:  55gr or lighter
    light twist: 1 in 12 or 1 in 14
    high velocity: at least 3300 fps
    normal bullets:  none of this SLAP crap

 You will never hear of stopping issues AGAIN.

 The Armalite Rifle model 15 was designed as a light, yet powerful carbine that was easy to handle, shoot and maintain....it has turned into a fat, ungraceful Camp Perry gun that is better at driving tacks than blowing off enemy body parts.
 Ya want heavy, go with a weapons system like the Stoner 63 ( my sweetie )...but there is no need for a general purpose rifle in 5.56 to weigh that much...that weight could easily be replaced by AMMO which the infantry can always use more of.

Call me on this... have some stuff here that you will be interested in.

Here's another one.  Split the lower receiver into two parts at the mag well.  Make the part that holds the hammmer/trigger/sear the registered part.  Then you could interchange uppers and magwells for different calibers/magazines.  This would be a concept similar to the HK series where the trigger pack groups are interchangeable between different guns.  

Get a 7.62x39 modular upper with a magwell that takes AK magazines.  Want cheap(er) 7.62x51?  Upper and mag well that takes FAL or G3 mags.  Want one in .30-06?  Assuming someone would make an upper in the longer length, just add the magwell that takes BAR mags.  

Or, go the other way.  Instead of a long upper/lower and and magwell adapters to handle .45 or 9mm mags, a short upper/bolt and an appropriately sized magwell to match your grease gun or UZI mags.

All you'd probably need would be some kind of a tongue & groove arrangement to match up the mag well to the fire control portion of the receiver.

How about a speaker system and electronics built into the buttstock that will play "The Ride of the Valkyries" whenever the charging handle is operated? [;D]

That would definitely be a nice evolution for the AR series!  It's impressive how many different caliber/magazine combos have been made exploiting the standard magwell, but interchangable magwells would make the possibilities almost endless!  You could make a specific magwell longer (ala the AR10) as long as the corresponding upper had the pivot pin hole in the right spot.

Dang, that beats the sound of a Mossberg 500 slide being raked when it comes to making a burglar soil himself.  [;)]

I would love to have a Pezz dispenser built into my ARMS SIR handguard! Neat Stuff!

LS

me being a composites freak
how about a carbon kevlar lower and upper
it should be quite light
similar to the carbon 15 ala bushmaster but with the cool weave

Light weight should be the name of the game for the sorry grunt who has to carry the weapon.

The single heaviest part of the rifle is the barrel.  

I envision a Titanium barrel in an HBAR contour with the heft of a pencil thin light weight.  Light weight contours could have the weight of a toy.

Potential problems of lubricity and galling of the Titanium down the bore could be solved by nitriding, which is supposed to be a superior surface treatment when compared to chroming.  

How does one rifle a titanium bore?  

Otherwise;
6.5MM caseless(or combustible case)with electric ignition(to solve primer questions), robust electronic range compensating red dot linked to display in helmet visor or goggle.

Belt fed.

The basic weapon could be upgraded to SAW capability.

The 20MM grenade launcher from the OICW should be a separate INDIVIDUALLY fielded weapon.  One weapon does not have to do everything poorly.  It can do one thing well.

Here's a thought on the "intermediate caliber, between .223 and .308"

Base diameter
.223 = 0.378"
.308 = 0.473
average = 0.4255"

Length case
.223 = 1.77"
.308 = 2.01"
average = 1.89"

Cartridge length
.223 = 2.25"
.308 = 2.81"
average = 2.53"

Caliber/bullet diameter
.223 = .223"
.308 = .308"
average = .2655"

So the all around average of the two is a case about 0.42" at the base, 1.89" long, 2.53" long loaded and in .264 caliber.  Sounds like the 6.5 JDJ to me - rimless that is

EDIT - Instead of reading my references at 0230, I should read them at 1430 ... The dimensions of that round are just about those of [drumroll] the 6mm SAW ... we've come full circle ...

Took a gander at some simulations, operating at a meager 50,000 psi
140 gr AMAX, 16" barrel, 2200 fps
95 gr V-Max, 16" barrel, 2700 fps

With 20" barrels, they go to 2400 and 2850 fps respectively ...

Nice little round ...
The 6.5 PPC does 2750 fps with 129 gr and 24", the JDJ does 2600 in my simulation.