Very nice collection !
What is the story on the 4 rounds in picture #14? Very interesting tip on the two bullets in the middle? Nice collection.
Sorry, I missed your question when you posted it!
The four rounds are (l. to r.)
.303 Brock Mark VIIK - anti-Zeppelin explosive used mainly by the RNAS 1916
.303 Pomeroy PSA Mark I - explosive 1916
.303 inch experimental "milk bottle" explosive 1918
.303 Buckingham Mark II - phosphorus incendiary/smoke tracer 1917
British Military Smallarms and Ammunition
Collector, Researcher and Pedant