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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 Phase 2 Consolidation and info   Small Arms <20mm

Started 30/8/19 by gatnerd; 547444 views.
stancrist

From: stancrist

3/11/21

EmericD said:

the blue curves are the measurements for 5 different shots (i7 around 0.89), and the red curve is the computed form factor (~0.75). You can see that the difference is real...

A perfect example of theory vs reality.

roguetechie

From: roguetechie

3/11/21

I like the von karman ogive a lot ...

Enough to ask why you think they can't be manufactured in bulk, because if they can't then obviously we should look elsewhere.

I'm just curious as to what precisely makes them unmanufacturable and whether that can be fixed with some of the modern manufacturing processes we can do affordably now that we haven't been able to in the past.

If there's a genuine issue with manufacturing that we can't solve that would be one thing, but if it's just a matter of we haven't done it yet then to me the obvious answer is to work out a way to do it.

I haven't seen a whole bunch of 100k psi TV stuff from him either, especially not after they FEA'd reverse engineered TV cases and concluded it's probably not a good idea to take them that high.

As someone who was around when bearcat and the most recent cartridge for it were conceived I'd conversely be very willing to pick up a bearcat that had been pull string fired 10 times and rattle off a mag dump without thinking twice about whether it'd hurt me or not. Then again, I know about how many iterations, material spec revisions, and FEA cycles the optimized bolt and locking interface went through and that it's way beyond a full 150% safety margin.

I also know about how many FEA cycles etc his other designs have went through and what the actual process was there.

What he presented here as bearcat went through an awful lot of changing, refining, FEA, and alterations for manufacturability before it ever showed up here.

I can understand how someone who has only seen what shows up here would think what you do, but as someone who has seen behind the curtain at the process that lead to bearcat and the VKO's etc (and has reference points about how other designs came to be from within the actual industry)

I'd be far more inclined to trust bearcat than to buy anything sig has been making for less than five years that isn't into at least it's second name change.

And that's kinda the problem, anyone who has a problem with what Nate does and how he does it would give up guns for Buddhism and zen gardens if they saw what the actual industry is doing in comparison!

This is sort of why I bother to have these conversations here. Because every once in awhile productive stuff does come up.

Things like why the VKO series would be hard or economically impractical to produce. That's something I'm genuinely curious about.

Especially now that emeric is putting the ADVAP at .87 which would seem to indicate that maybe these projectiles can be produced economically now.

roguetechie

From: roguetechie

3/11/21

It's almost like I was right about sig's case option being the most expensive and least practical or something...

I do genuinely hope that it's not as prone to casehead separation as it looks like it could be though, that would be bad.

roguetechie

From: roguetechie

3/11/21

Yes, I also know that those same solids need to be retested with the suggested twist rate barrel before we have anything like a hard evidence smoking gun that calculated versus actual are that far divergent.

It was a good test and believe me you made lots of people very happy by doing it since it's beyond our abilities to do ourselves.

Those tests and the data from them were very valuable and a good step towards getting something that will work in the future.

Acting like one test of a very small lot of ONE DESIGN out of a barrel that wasn't actually the twist rate it was meant for is open and shut conclusive evidence of anything is.... Specious.

Especially when, OH NO it only ran at a .89 FF which is... .022 off 6.8 ADVAP!

It's... .022off advap *insert despicable me whiteboard meme here*

Think about what you just said and the dismissiveness you said it with for a second. 

First real test solids he's had a chance to see made and tested and he's a whopping .022 FF behind ngsw...

What do you want to bet that If a second revised design of what he sent you gets tested in the right twist rate they'll meet or very likely exceed the FF of ADVAP?

Considering how iterative bullet design is and has always been that's a pretty safe bet right?

It's not something I'd bet against.

I mean, since we're "putting things in perspective here", let's actually put some things into perspective.

For a first batch of test solids from someone who has only been able to work in digital format with no real world testing that's pretty close to a home run.

It's not a grand slam, but he definitely didn't "only get a base hit here"

And therein lies the frustration. 

nincomp

From: nincomp

3/11/21

"Excuse the profanity, but it's about fucking time militaries got their act together on good ballistic shapes, hopefully others will follow suit"

The "ballistic shape issue" has been a big topic on this forum for very long time.  The US, in particular has been designing cartridges that do not permit long ogives for decades.  Even cartridges designed for long ranges, like the 7mm Rem Mag used relatively stubby bullets.  

The design of the 5.56x45, I understand.   I recently watch a few hours of filmed interviews with Eugene Stoner and he was adamant that his cartridge only needed an effective range of 300m.   He argued for fixed sights since the did not think that soldiers would ever need to adjust for elevation.  I find it interesting that the Russian 5.45x39, more or less a response to Stoner's cartridge, took such a different approach and took aerodynamic efficiency much more seriously.

Once a bunch of weapons have been designed around a particular cartridge like the 7.62x51, it is difficult to make a large change.  I am interested the the concept of utilizing neckless cases in existing chambers to allow bullets with longer ogives, but am aware of virtually no work on solving the accuracy problem created by the long jump to the lands.  It would appear that research on this issue would benefit the CT rounds as well as the TV neckless.

  • Edited 03 November 2021 14:47  by  nincomp
smg762

From: smg762

3/11/21

The 5.45 has a great shape but is let down by poor energy and light bullets...AK74 never had a very long barrel either.

5.8chinese has about 200ft lbs over 556 but a poor bullet shape.

Instead of neckless i think you are better chambering your ar15 for a 224valkyrie or similar 6mm.....25rnd magazines are a minor drawback.

Frankly the US could have avoided NGSW by converting ARs to a really hot souped up valkyrie round.

On subject of NGSW, what will UK, france and germany do if it gets adopted by US?

EmericD

From: EmericD

3/11/21

smg762 said:

5.8chinese has about 200ft lbs over 556 but a poor bullet shape.

If i7 of 0.95 (DBP10), 0.96 (DBP191) or 0.97 (DVC12) are "poor bullet shape", then what about the 1.18 i7 of the M855A1!

The mighty M855A1 is delivering 280 J at 600 m from a 12.3 g cartridge, that's 23 kJ per kg of ammo.

The 7N6 is delivering 300 J at 600 m from a 10.5 g cartridge, or a specific energy of 29 kJ/kg (+25%).

The 7,62 x 51 mm DM41 is delivering 920 J at this same range from a 24.0 g cartridge, or a specific energy of 38 kJ/kg (+65%).

The DBP10 is delivering 530 J at this same range from a 12.9 g cartridge, or a specific energy of 41 kJ/kg (+75%).

The 6.8 x 51 mm should be close to 1500 J, so even with SIG ~22 g cartridge that's a specific energy of 68 kJ/kg (+200%), and more than 80 kJ/kg (+250%) for Textron or True Velocity.

roguetechie

From: roguetechie

3/11/21

The new Chinese 5.8 rounds looked really nice to me but that breakdown you just did certainly puts things into perspective.

And oh wow a 1.18 ff for m855a1 is pretty ouch. 

Would you happen to have the ff of the 62 grain mk318 mod 1 on hand?

Also do you know how much of that .1.18 i7 is down to the EPR gap they had to leave to get reliable terminal effects by chance?

stancrist

From: stancrist

3/11/21

Is there a useful purpose for the "specific energy" comparison?  Because I  sure don't see a logical reason for it.  Nobody shoots a kilogram of ammo into one enemy soldier.

  • Edited 04 November 2021 0:13  by  stancrist
renatohm

From: renatohm

3/11/21

In practice theory is different.

Or

Even parrots can talk, doing is another thing altogether.

Common phrases in Brazil, mine aren't perfect translations but stress your point: until it's proven it's only an idea, no matter how good it seems to be.

I must say that even when proven you can still debate whether the testing was adequate, the world is full of stuff that worked like a charm during testing but failed miserably in the real world (eg the Soviet tank busting dogs).

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