German-USSR trade was still ongoing in 1941. As part of that trade they did gain access to samples of German artillery, tanks and more. German companies were also known to export arms (in violation of the Versailles treaty) well before WWII. And even if you deny that, there were dozens of countries manufacturing arms and ammo in the German caliber because, get this, German guns were well designed!
Dismissing all evidence that could put Soviets in a bad light, even when it's internal. Truly you are a Communist at heart.
So let's put all that aside: capturing thousands of POWs and having them end up massacred in a ditch is acceptable? There's no fault attributable to them for having this happen to people in their control and under their protection?