He is very knowledgeable. He is very friendly and will try to help you. Most of these have been similar to the 7.7 Jap Observation bullets or the WWII German B-Patrone. These are more for observing impacts and directing fire than for explosive effect. I have tested some of these in the 7.9x57, 7.65x54 Argentine, 7.7 Japanese and 7.62x54R Russian, all WWII vintage, and while I wouldn't care to have one strike near me, they are pretty pathetic as a military round.
Penetration is poor.
Upon firing the firing pin is carried back to the read under its own interia, safely away from the percussion cap. For military purposes these small caliber rounds are far inferior to later API or APIT rounds. I believe the Navy interest is primarily in the cal. This, if I remember correctly has a tungsten carbide core and a charge of about 2 grams of RDX which is initiated upon impact, so you get the dual-purpose of fragmentation and a good visual indication of the impact, plus the AP effect of the heavy metal core. The penetration of this round probably isn't much better than the WWII era API M8, but the explosive effect is pretty good, and you can distinctly see impacts with the naked eye on a sunny day to 2000 yards.