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Military Guns and Ammunition

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This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons.

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NGSW Reset / Change in Direction   General Military Discussion

Started 16-Nov by Guardsman26; 13306 views.
nincomp

From: nincomp

23-Nov

stancrist said:

Until you mentioned it, I haven't seen anyone talk about geometric volume.  As I understood the comments made by others, everyone seems to have been referring to what you call "effective volume" when discussing the volume of a cartridge.

It was the slide from the 2016  6.5 CT presentation that got me thinking.  It stated an 18% volume reduction vs 7.62x51.  It did not state whether this was the geometric volume, the effective volume when stacked in a magazine (ie,  the tapered-cylinder model for 7.62x51), or belted.  As you pointed out, the style of magazine would have some impact here.

For belted ammunition, when the cartridges are loaded parallel to each (pointing the same direction*), distance between cartridges is constrained by its widest dimension.  When belted, wide cases (even if holding small-diameter bullets), large tapers and the presence of rims increase the relative volume per round and reduce the number of round that would fit in an ammo box.   The parallel-sided CT cartridge could have an advantage here.

The "effective volume" of a given cartridge could change again when packaged in bulk.  Here, the orientation of the individual cartridges does not matter and packed volume can be minimized.  For example, 20-round boxes of 7.62x39 cartridges that I have from Barnaul are smaller than their Remington counterparts since Barnaul alternates the orientation of each cartridge to take advantage of the taper and Remington uses a plastic holder and orients each cartridge in the same direction.  

It is possible that some cartridges that have a relatively wide case and narrow bullet can be optimally packaged in layers of two rows with the bases facing opposite directions and the bullets interleaved.  This might be the case for 6.5 Creedmoor (or more likely, 6mm Creedmoor), but I have not tried it.

*No, you don't need a few cartridges facing backwards, "just in case there are enemy behind you." 

stancrist

From: stancrist

23-Nov

nincomp said:

It was the slide from the 2016  6.5 CT presentation that got me thinking.  It stated an 18% volume reduction vs 7.62x51.  It did not state whether this was the geometric volume, the effective volume when stacked in a magazine (ie,  the tapered-cylinder model for 7.62x51), or belted.  As you pointed out, the style of magazine would have some impact here.

The type of magazine only affects magazine volume.  It has no impact on the cartridge volume, which is what the RDECOM slide shows.

That slide seems to compare cylindrical volume of the cartridges, although it inexplicably lists 0.487" as the case diameter of 7.62 NATO.

(Note:  Calculating the volume of a 0.47" x 2.80" cylinder gives the figure shown for 7.62 NATO volume in that table.)

nincomp said:

For belted ammunition, when the cartridges are loaded parallel to each (pointing the same direction*), distance between cartridges is constrained by its widest dimension.  When belted, wide cases (even if holding small-diameter bullets), large tapers and the presence of rims increase the relative volume per round and reduce the number of round that would fit in an ammo box.   The parallel-sided CT cartridge could have an advantage here.

No way.  Since the CT rounds are larger in diameter, a belt of linked CT ammo will necessarily be longer.

nincomp said:

The "effective volume" of a given cartridge could change again when packaged in bulk.  Here, the orientation of the individual cartridges does not matter and packed volume can be minimized.  For example, 20-round boxes of 7.62x39 cartridges that I have from Barnaul are smaller than their Remington counterparts since Barnaul alternates the orientation of each cartridge to take advantage of the taper and Remington uses a plastic holder and orients each cartridge in the same direction.  

It is possible that some cartridges that have a relatively wide case and narrow bullet can be optimally packaged in layers of two rows with the bases facing opposite directions and the bullets interleaved.  This might be the case for 6.5 Creedmoor (or more likely, 6mm Creedmoor), but I have not tried it.

None of those methods are how US military rifle ammo is packaged.

The fatter Textron CT cartridges will require bigger 20-round cartons.

roguetechie

From: roguetechie

23-Nov

BINGO!

Stan has hit on the actual crux of the issue here!

Before rounds can be loaded into mags and jammed in pouches, they must first make it into the operating theatre.

At one point In the LSAT program there was a slide showing a pallet of 5.56 LSAT next to a pallet of 5.56 which illustrated an ability to either physically get more rounds into a pallet with the same weight and physical dimensions as a current pallet of 5.56 brass case or to get a smaller lighter pallet stack that contains the same number of rounds.

The logistical back end is at least as important if not moreso than how many loaded mags we can attach to a single infantryman.

stancrist

From: stancrist

23-Nov

roguetechie said:

At one point In the LSAT program there was a slide showing a pallet of 5.56 LSAT next to a pallet of 5.56

Are you sure about that?  I was interested in seeing the difference, but the only LSAT slide I found that came close to matching your description does not have such a side-by-side comparison.

Slide 18 -- Slide 1 (usgovcloudapi.net)

smg762

From: smg762

7-Dec

in practical magazine size does the textron round reduce mag volume compared to the others?

stancrist

From: stancrist

7-Dec

No.  Using the dimensions posted by Emeric in Msg 66, I calculate the Textron magazine to have a volume slightly greater than the others.

nincomp

From: nincomp

8-Dec

smg762 said:

in practical magazine size does the textron round reduce mag volume compared to the others?

As Stan said, from the little we know, the CT ammo does not look smaller than the competitors.  Remember though, we do not know a hell of a lot of details at the moment.   There is not enough info to make an apples to apples comparison.  We really can't make accurate comparisons yet since the proposed weapons use different length barrels and we don't even know the muzzle velocities.

The True Velocity neckless cartridge, for example, uses a longer barrel and runs at lower pressures.  It appears that it is effectively a lower power cartridge than the other two.  IF True Velocity were to make a neckless cartridge to match the short-barrel performance of the others, would it need to be significantly larger?

In previous posts, I discussed info that Textron had released several years ago about its 7.62, 6.5, and 5.56mm ammo.  In THOSE cases, the volume of the CT rounds was less than that of the brass-cased equivalents.  They were larger diameter, but significantly shorter.*   That volume reduction was compared to "standard pressure" cartridges, however.  It is entirely possible that the Textron CT ammo loses its volume advantage when compared to higher-pressure cartridges like the Sig Hybrid.  It remains to be seen how it would compare to a comparable TV neckless cartridge.

*Lower volume would definitely have an impact with bulk shipments, but it gets more complicated when it comes to the amount of ammo an individual solder would carry.  That would depend on the shape of magazines and how they would be carried.

  • Edited 08 December 2021 0:24  by  nincomp
gatnerd

From: gatnerd

8-Dec

nincomp said:

That volume reduction was compared to "standard pressure" cartridges, however.  It is entirely possible that the Textron CT ammo loses its volume advantage when compared to higher-pressure cartridges like the Sig Hybrid.  It remains to be seen how it would compare to a comparable TV neckless cartridge.

One thing I've wondered about CT ammo is how projectile length and shape effects the cartridge. 

With a conventional case, you can stuff basically anything into the cartridge thats within ogive length.

For example, a .224 Valkyrie could load every one of these projectiles without issue:

With CT, I wonder if thats the case? Or does each cases internal geometry and overall length need to be tailored to the projectile? 

In reply toRe: msg 78
gatnerd

From: gatnerd

8-Dec

Some SIG NGSW spin offs - the SIG Raptor, a 7.62/6.8x51 8" barrel PDW based off the their NGSW Spear. 

NEW Sig MCX Raptor: A Mini-Spear or a Mega-Rattler?

In this episode of TFBTV, James Reeves is at Sig's headquarters speaking with Jason St. John about the NEW Sig MCX Raptor. The MCX Raptor is a shorter-barrel...

Farmplinker

From: Farmplinker

8-Dec

Is Sig getting subsidies from hearing aid manufacturers?

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