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File 143525713260.jpg - (31.87KB , 500x230 , lsat_a.jpg )
7213 No. 7213 ID: 8aafcd
Okay, so I know how regular cased ammo works. But I never could wrap my head around how both caseless and "cased telescopic" ammo works. Both types of ammo (in the pic) have the bullet buried inside the propellant. I don't quite understand how that is supposed to work (but it does, as evidenced by the LSAT machine gun).

I can understand how regular cased ammo works because all the propellant is behind the bullet, so it makes sense to me that when the propellant is ignited the bullet is launched forward out of the gun - the opposite direction from where the propellant exploded. But with caseless and telescopic ammo, all the propellant is AROUND the bullet, yet the bullet somehow still launches forward out of the barrel.

I can't quite understand that because, in my mind, since the propellant surrounds the entire bullet instead of only being behind it, I would have thought that when the propellant is ignited all around the bullet, the bullet doesn't really go anywhere or else exits the barrel at a very low velocity. Yet they've proven that building ammo in such a way can have just as much velocity as regular cased ammo.

So can one of you who have a better grasp of physics and firearm mechanics explain how this ammo works to me? Thanks.
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>> No. 7214 ID: fb3bdd
They have a booster charge right behind the bullet which ignites first.
>> No. 7215 ID: 06a0fb
This. Theres a two-stage primer system in the LSAT cased telescoping ammo. First primer begins igniting the propellant and ignites a second a second smaller primer, which forces the bullet up to the mouth of the cylinder seal. By the time the bullet has moved to fully seal the cylinder, the propellant has burnt enough to begin propelling the bullet down the rest of the barrel at desired velocity.

In the fully caseless ammo, the plasticized propellant takes longer to ignite by nature, so a single primer does the same thing, the bullet being pushed just far enough to seal the chamber by which point burning of the propellant is advanced enough to push the bullet all the rest of the way out the barrel.
>> No. 7216 ID: 381ee6
The entire idea behind telescoping ammo isnt that it's caseless, caseless can be made fairly easily today
Rather the idea is that the powder load is distributed around round thus making it lighter, more compact (or more powerful if you want), and of a regular size and shape
This makes feeding machine guns way easier
>> No. 7217 ID: 51dbcb
Caseless also heats up the chamber more, because with a case a lot of heat is just thrown out when the case is ejected. This is however not the case when there is no case. :)

There's various other issues, like throat erosion due to how differently the caseless bullet will engage the rifling compared to a normal conventional cartridge. (also causes it to likely be less accurate)

Or the fact that if a round cracks in the gun, it's fucked up to get it out. Misfired rounds are less problematic but still annoying.

Still lots of issues to resolve.
>> No. 7218 ID: f013be
You're talking about caseless of the type used in G11?
>> No. 7219 ID: 06a0fb
>Still lots of issues to resolve.
Which should start getting done here by this July or August, as the Marine LSAT caseless versions for testing should be received around that time from ATK.
>> No. 7228 ID: 3254ec
How's the 5.56 LSAT doing?

Because it actually has a chance in the short term of being adopted.
>> No. 7231 ID: 06a0fb
Testing is almost complete on the 5.56 variant. Textron is making a 7.62 variant , which they unveiled at SOFIC this eyar.

For the 5.56 variant, all the army needs to do is say, adopt it or dump it.
>> No. 7245 ID: 3254ec
Good, pit it up against the Stoner LMG and anyone else who can put out a sub 12lb belt fed LMG (read: clearly not H&K), we're past due to kick the SAW to the curb.

Just to reiterate the MG4 is a joke, so is the M320
>> No. 7252 ID: 06a0fb
I think the army is waiting until a 7.62mm variant is developed by Textron to decide what to use. If we can get a similar weight savings to the 5.56 LSAT LMG over the SAW, with a 7.62mm LSAT over the M240B or even M240LW or Barret Lightweight, say sub 13-pounds loaded in 7.62 with the CT ammo, I think the Army will adopt that over the 5.56 variant for increased effective and terminal range, lethality, barrier penetrating performance, and still being lighter than almost every other 5.56mm LMG out there while bringing GPMG performance.

Then again, I'm the kind of idiot who thinks the Army and Marines should be dropping the M240s from vehicle mounted applications and using that .338 Norma Mag LWMMG from General Dynamics in the vehicle mounted role, especially in the face of all these new MB Jeep-like concepts all the SOF and battalion-level recon forces are wanting to move to.
>> No. 7426 ID: 943d55

If we're talking fullpower 7.62x51mm M80 Ball here, if the platform is TOO light, it's not controllable in full auto any more, right? Controllable full auto fire is why the beltfed stuff exists. 13 pounds might even be pushing it.
>> No. 7437 ID: 06a0fb
Controllability during full-auto fire is changed due to the feed mechanism of the swinging chamber necessitating a reduced rate of fire for proper synchronization of all the mechanisms, and because of the reduced weight of the bolt caused by the new chamber and loading mechanism.

Attached video demonstrates the way in which the weapon loads and shows the arrangement of firing pin, chamber, and leading tray which improves handling and reduces reciprocating weight of a traditional bolt in heavier mechinegun styles.

I'm trying to embed with the video starting at the pretinent bit, but if it doesn't work, 1:09 is the teardown right before the bolt operation animation.

the Caseless version has a a combination of this swinging chamber design and also a clamshell-like two-piece chamber which opens for new round insertion but then closes for ignition. A PDF from an official update on the weapons gives a rough idea of how the caseless chamber works, linked here:
>> No. 7438 ID: 06a0fb
File 144471548364.jpg - (93.10KB , 651x560 , LSAT5_56&7_62.jpg )
Also, this is a pic of the size comparison of the standard 5.56 M855 and 7.62 M80 against the LSAT caseless 5.56 and 7.62 versions.

Case capacity for powder is roughly 115% that of the traditional brass cased for 5.56, and the case weight is down to 63% fully loaded vs. M855. 7.62 has not been finalized in design and materials yet, so final differences between it and M80 aren't known.
>> No. 7522 ID: 06a0fb
bumping to the top of the board. Found this article looking for updates on the CL LSAT and Marine Corps testing, and found this article

Special mention is made under ammo developments and the apparent study of a round called .264 USA as a proposed intermediate cartridge for adoption.

I haven't heard about the round before; is anyone else up on it? They also make mention that Lake City is making conventional-layout polymer cased/brass base ammo for a 2016-2017 ammo study.

Is anyone else hearing this kind of stuff or is this all bullshit being pulled from nowhere?
>> No. 7561 ID: 589262
sweet, LSAT update.

here's info on .264 USA: http://www.thefirearmblog.com/blog/2014/11/10/usamu-264-usa/
>> No. 7562 ID: a4acc8
>is a 6.5mm caliber round, based on lengthened 7.62×39 brass
Russians are building literally the same fucking round.


Could this be the "convergent evolution" everyone is talking about?

If American gun producers start talking about a .500 cartridge for assault rifles, DMRs, sniper rifles and machine guns, I'm going to shit a brick.

>> No. 7566 ID: 06a0fb
.264 seems significantly longer than 7.62x39, .264 being .31 inches longer, and a millimeter greater width in the case shoulder on .264. Case base to shoulder is much larger in .264, 1.1606 inches in 7.62, but 1.3901 in .264.

That 6.5mm russian stuff is almost exactly 6.5 grendel, but dimensionally both are still smaller in length, and base to shoulder length. It seems .264 uses a slightly smaller base diameter than 7.62x39, .4449" vs x39's .447". probably to address the AMu's desire for less case taper than the x39 case has.

Who knows, if this is all development of an intermediate load for the LSAT, brass case dimensions won't mean much for the final product.
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