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

That provides a pretty solid baseline for what we know (rather then hope) is possible with EPR manufacture. Its certainly a step up from that M80A1...

poliorcetes said:

I still don't remember why not an entire steel case instead of such complicated design

I imagine it's that the base is a hardened(ish) sturdy steel alloy for handling high pressure vs the malleable steel used to form like a 7.62x39 case.

Such an alloy / hardness probably cannot be 'drawn' like brass/mild steel and has to be machined or MIM'd, necessitating the multi piece construction.

That actually raises a very interesting question for both SIG and TV's cases. Namely, are their Steel Bases MIM'd or do they have to be machined on a swiss lathe (like a copper solid target bullet.)

If the bases are MIM, then affordable mass production is possible. If the bases have to be machined then cost is going to be high. The rough grey finish of the TV bases look suggestive of MIM to me, whereas the more shiny steel of SIG's base looks machined. But I have a pretty limited manufacturing experience - sending my sketches out to contract manufacturers is about the extent of my hands on experience with metal work. 

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...

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? 

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

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.)

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...

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

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.

roguetechie said:

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

Ditto.