Some exterior ballistics results achieved recently.

First, we wanted to check the "scaling effect" that seems to "plague" the development of Very Low Drag 5.56 mm bullets.

The 224 D v1 (5.56 mm) bullet was as similar as possible to the 327 D (8 mm) bullet, but scaled down. Our first indoor (0-200 m) radar results (measured in December 2021) indicated that there was no scaling effect at high Mach number, but the latest results (with a tracking radar, up to 2000 m) showed a small (~3%) increase of the drag of the 5.56 mm bullet vs. the 8 mm version.

It's difficult to tell if it's a scaling effect, or a small difference in the actual bullet shape (we are talking about effects caused by fraction of mm).

Anyway, we can now firmly draw 2 conclusions:

• the bullet C7 is confirmed at 0.208 in the supersonic domain, not bad for a bullet that is only 26.9 mm long, with a weight of 4.13 g.
• the bullet is not very well guided into the barrel, resulting in large bullet initial yaw and poor accuracy. 

A variant of this same bullet, but with a conventional conical boat-tail was tested, in order to achieve better accuracy, and the result was exactly that.

The large initial yaw was suppressed, and the bullet is now well guided, with "match like" accuracy.

Unfortunately, the "classic" conical boat-tail looks less effective in the supersonic domain than the truncated ogive of the original "balle D" (but it's way better in the subsonic domain, which is not really needed), so the C7 is now only 0.201, "not bad" but of course less than expected.

Muzzle velocity is OK, the powder load was 1.68 g.

All in all, this combination (0.20 C7 and 920 m/s MV) is already delivering more than 500 J at a range of 600 m, and a supersonic range close to 900 m.

We are working on a "no-WC" AP version of this bullet to see what could be done against ceramic hard plates, and maybe perform some tests with the 224 Valkyrie rifle we have now.

The AP bullet will weight around 55-57 grs, so with the 224 Valk maybe we could achieve an impact velocity above 800 m/s at 250 m.

I have wondered if the drag of very highly optimized bullet shapes would be very sensitive to angle of attack.    What was the max angle of attack that would retain the anticipated BC?   

EmericD said:

Muzzle velocity is OK, the powder load was 1.68 g. All in all, this combination (0.20 C7 and 920 m/s MV) is already delivering more than 500 J at a range of 600 m, and a supersonic range close to 900 m

Awesome results, thank you so much for sharing.

The bullet shape seems very good. I recall you were working on 'cold pressing' them, has any progress been made there for a way to produce them economically at scale?

As far as the case design goes, is the plan still a TV style 'neckless' polymer case? 

gatnerd said:

The bullet shape seems very good. I recall you were working on 'cold pressing' them, has any progress been made there for a way to produce them economically at scale?

Not as fast as I would like, and just when we managed to demonstrate the first steps, there is now a requirement to give them AP capability...

gatnerd said:

As far as the case design goes, is the plan still a TV style 'neckless' polymer case?

The stainless steel case subprogram is advancing way faster than the polymer case subprogram.

Lightweight stainless steel case provides ~12% more case capacity than brass case, and could work (i.e. very good bullet retention) with very short necks...

EmericD said:

The stainless steel case subprogram is advancing way faster than the polymer case subprogram. Lightweight stainless steel case provides ~12% more case capacity than brass case, and could work (i.e. very good bullet retention) with very short necks

Thats exciting to hear about SS. I had been very bullish on SS when they had first come out as pistol rounds, and then the technology seemed to languish for years, at the same time TV polymer seemed ascendent. I had thought SS had missed its moment and would go the way of Betamax. 

But now it seems SS is hitting its stride. First with the FN .264, then their commercial .300blk cases were released, and now with your high performance 5.56 project (do we still call it 'neckless' if theres a short neck?)

When SS first came to market they advertised a 50% case weight reduction, but that was with an Aluminum case head / thin steel body. Now that they are using a steel case head, what type of case weight reduction do they offer?

Also earlier in the .264 thread, you had mentioned the SS cases performed similarly to lubed ammo, in that they resulted in more (30%?) bolt thrust. Has this been the experience with the 5.56 cases, and if so, do you think this will effect bolt life on the 416 / 5.56 rifles in general?

Lastly, you mention that SS is advancing way faster than the polymer case. Is this due to still unresolved problems with polymer cases, or just SS being easier to work with / get launched? 

Thanks again for sharing this project with us. 

gatnerd said:

But now it seems SS is hitting its stride. First with the FN .264, then their commercial .300blk cases were released, and now with your high performance 5.56 project (do we still call it 'neckless' if theres a short neck?)

It's thin stainless steel case, but they are not from Shell-Shock, and are made differently. And yes, they are not really "neckless", the 260 Remington is just similar to nickel plated brass case...

gatnerd said:

Also earlier in the .264 thread, you had mentioned the SS cases performed similarly to lubed ammo, in that they resulted in more (30%?) bolt thrust. Has this been the experience with the 5.56 cases, and if so, do you think this will effect bolt life on the 416 / 5.56 rifles in general?

Since those case are not made the same way than the Shell-Shock cases, they behave just like a regular brass case.

Ah very interesting. So you’re working with another style of stainless case, and they behave like brass in terms of bolt thrust.
 

Are they like the previous GD design where the thin wall stainless steel goes over an internal base that holds the primer? Or something new entirely?

Give him time to get the patents filed......