All I can offer at the moment is SAAMI’s glossary definition:

Ammunition, Reference – Ammunition used in test ranges to evaluate test barrels, ranges and other velocity and pressure measuring equipment. May also be used as a control sample by which other characteristics are compared, such as accuracy, patterns, etc.

Footnotes / Sources:

“Glossary ⇒.” Sporting Arms and Ammunition Manufacturers’ Institute. Ed. SAAMI’s Technical Committee. Web. 15-18 Jan. 2011.

Question:

• Do you have experience with reference ammunition?