couple of questions about the 224....

would it be overbore, as a military round, especially in a SAW or minimi?

does it tend to reach the advertised energy (wiki) from a long barrel or could it be managed in a 17 inch?

would the overbore problem be solved if the rifle was semi- only, and the MG used some kind of rotating chamber?

smg762 said:

would it be overbore, as a military round, especially in a SAW or minimi?

The 224 Valkyrie case capacity is slightly higher than the 5.56 mm (34.5 gr H2O vs. 31 gr), we are not talking about 22-250 case capacity (43+ gr).

http://kwk.us/cases.html

smg762 said:

does it tend to reach the advertised energy (wiki) from a long barrel or could it be managed in a 17 inch?

The 80.5 gr Berger loaded in the Federal Gold Medal is advertised at 2925 fps (892 m/s and 2075 J) and we measured 825 m/s from a 18" barrel, for 1775 J of muzzle energy.

what are your thoughts on say, a 300blackout CBJ for military use?  you could load it with a .19 cal steel bullet and maybe widen the case slightly to match valkyrie energies 

also i had a random question, what's the max weight you could reach with, say, a 4.7mm bullet?  60 grains?   i know the 4.6k HK has 90grain subsonics but i mean a regular ball round

Most commercial market .19 bullets are 35-low 50s. So possibly a 55-grain bullet, depending on various factors.

what would the BC be like on a 55grain .19?

and if you had a hypothetical 75grain tungsten bullet at 4.5mm, would that have a high BC?

Don't have it in front of me, but you can search engine  "ballistic coefficient calculator" and you can find the information at  a few sites.

smg762 said:

what would the BC be like on a 55grain .19?

BC is sectional density (SD) divided by form factor, so a 55 gr / .19 cal bullet with the G7 shape would have a 55/0.19²/7000 = 0.218 C7 BC. If the bullet shape is closer to the M80 or M855, which have a form factor around 1.12, then the BC will be only 0.218/1.12 = 0.194, but if the shape follows the Mle 1898D bullet then the BC will be 0.218/0.90 = 0.242.

smg762 said:

and if you had a hypothetical 75grain tungsten bullet at 4.5mm, would that have a high BC?

The increase of BC will follow the increase of SD, so instead of 0.218 it will be 75/55*0.218 = 0.297.

But pushing a 75 gr / 0.19 cal bullet will be very difficult and practical muzzle velocity limited...

the 762 DUDS used a .17 bullet at 55grains.  in theory, then, a 4.9mm bullet should reach 75grains with tungsten

If they had introduced a 6mm Valkyrie instead of the 224 the bullets could have been a little heavier (say 82gr) at the same velocity a 5.56 propels the 62gr with the extra mass helping defeat armor.  It may not do it at 600yds but may at normal engagement distances of 300.