It's not clear what the prototype munition actually is. The manufacturer, Rheinmetall, declined to provide further information to BI, citing Ukraine's security interests.

Rheinmetall, Germany's largest arms manufacturer, is currently focusing heavily on artillery production for Ukraine, with a plan to send hundreds of thousands of rounds — including some of the new prototype — within the year, Handelsblatt reported.

The longest-range munition supplied by Germany to Ukraine so far is the Vulcano, according to Ukrainian military news site Defense Express. Berlin has sent an unconfirmed quantity of this munition to Ukraine since the start of the conflict.

According to its manufacturer, the Vulcano is highly compatible with existing artillery systems and its guided version can travel up to 43 miles.

Before Russia's full-scale invasion, Rheinmetall was producing 70,000 rounds a year — a figure that is expected to balloon to 700,000 this year, Handelsblatt reported.

That figure would likely lead to a significant increase compared to Germany's ammunition supplied to Ukraine thus far. As of late April, the country had sent 81,500 155mm rounds in total.

Ukraine gets through a reported 6,000-8,000 rounds a day, per the AP.

But much of the company's capacity to ramp up production in the future depends on investment from the German government, Rheinmetall's CEO Armin Papperger told Handelsblatt.

Earlier this year, Germany announced a $5.3 million military aid package for Ukraine, including 10,000 artillery rounds from its own stocks, Politico reported.

Germany's Chancellor Olaf Scholz has trod a careful line in his country's provision of military aid.

Behind only the US and European institutions as a bloc in terms of the dollar value of aid, Scholz has nonetheless hesitated to provide more-lethal weapons to Ukraine.

Germany only allowed the transfer of Leopard tanks after months of international pressure, and it now faces continued calls to follow the UK and France's example in sending long-range cruise missiles.