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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; 522151 views.
EmericD

From: EmericD

3/11/21

gatnerd said:

What is the estimated Form Factor for the 6.8 GP EPR that has been shown?

Here is my estimate of the XM1186 bullet:

The i7 is around 0.87, for a 0.29 C7 if the bullet weight is 135 gr.

Combined with a MV of 2850 fps (869 m/s), that's good for a residual MV of 341 m/s at 1200 m, or exactly Mach1.0 at 1200 m...

gatnerd

From: gatnerd

3/11/21

Wonderful, thank you for doing that analysis. 0.87 is a very nice form factor, especially for mass production. 

Now, do you think, given the copper and steel of the GP, that it would be 135gr? Or more like 125gr as another member here estimated (somewhere) in the last few pages of this thread? 

poliorcetes

From: poliorcetes

3/11/21

Thanks a lot. Crystal clear.

I wonder if the pressure requisite is motivated by an objective of saving tungsten as much as possible (or even entirelly) against body armor... but such arrow-shield competition is quite bias against the bullet, at least for now.

But then I can't understand the rejection of the beretta solution for a rifle (for MG is an entirelly different matter). I mean, the more barrel lenght, the better for Eo and Eo is what it is being looked for.

Anyways, if you are right I just don't understand why SiG have any possibilities. IF CT problems can be enough mitigated, then weight and costs savings would obliterate that machined steel plus brass complex case

gatnerd

From: gatnerd

3/11/21

poliorcetes said:

But then I can't understand the rejection of the beretta solution for a rifle (for MG is an entirelly different matter). I mean, the more barrel lenght, the better for Eo and Eo is what it is being looked for.

I am a hugeeee bullpup guy. The majority of my personal rifle collection are bullpups. Really into them both personally and as a concept. 

But from that G&A article on the RM277, I came away less enthused by the design, at least in its state of development that it was reviewed by G&A.

At 10-10.4lbs, its 2lbs heavier then a) the other NGSW rifles b) a good deal heavier then current commercial 7.62 bullpups. When we also factor in the likely 2lb NGSW-FC, plus the heavish ammo, plus whatever battery pack its going to use... reducing rifle weight is going to be at a premium.

The controls (open vs closed bolt option, unusual safety, odd sliding bolt release) also did not look as intuitive as I'd like. Controls wise both the AUG/F2000 and now X95/Tavor 7 / DT MDX all looked much more intuitive and easy to pick up. 

So while I do think Bullpup is the way to go for maximum AP ability, I can see why this particular bullpup is struggling. 

On the positive side, they did report near 1 moa accuracy, and the bullpup is remarkably short and size efficient. It might be the most size efficient in the world (32.25" w/ 18.5" barrel + suppressor is super short.)

EmericD

From: EmericD

3/11/21

roguetechie said:

I'd love to see his stuff actually get proper testing and development to be honest.

I dunno if that could be called "proper testing", but here are some bullets manufactured:

Those bullets were then loaded:

and fired for accuracy:

then with a radar to determine the CD:

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...

Gr1ff1th

From: Gr1ff1th

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

stancrist

From: stancrist

3/11/21

Gr1ff1th said:

And for the record I am not Anti-Nathaniel,

Nor am I.  Actually, I have quite high regard for his knowledge and talent.

All I'm saying is that it is not logical to tout unproven designs as solutions.

stancrist

From: stancrist

3/11/21

roguetechie said:

I'd love to see his stuff actually get proper testing and development...

Ditto.

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.

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