Editing Project HARP (section)

=== 7-inch gun systems ===
The 7-inch HARP guns functioned as scaled-up versions of the 5-inch HARP guns that could carry three times the payload with an altitude capacity of 350,000&nbsp;ft. The 7-inch gun system was constructed from a 175&nbsp;mm [[M107 self-propelled gun|M113]] gun whose barrel was smooth-bored and extended by 26&nbsp;ft. In general, its projectiles were 1.6 m long and weighed 27&nbsp;kg.<ref name=":11" /><ref name=":14" /> However, it was also capable of firing 5&nbsp;kg slugs at a muzzle velocity of 2,880&nbsp;m/s.<ref>{{cite report|url=https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/ADA300522.xhtml|title=Ballisticians in War and Peace|last=Reed|first=Harry|date=1992|publisher=Ballistic Research Laboratory|volume=3|id=ADA300522|access-date=February 11, 2020|via=National Technical Reports Library}}</ref> The 7-inch HARP gun also incorporated the use of gun-boosted rockets to increase payload and altitude capacity. Unlike the 5-inch HARP guns, all vertical high-performance flights for the 7-inch HARP guns were conducted at NASA's [[Wallops Island]] facility, where 34 vehicles were launched by May 1966.<ref name=":14" />