Projectile Range and Instrument Rooms
Building number 620c

"Building 620C" actually comprised two small frame additions to Building 620 as well as two other structures originally designated as Buildings 622 and 646. The facility was built in 1943 for ballistic acceptance testing of special nitroglycerine stick powders. It consisted of a U-shaped, flat-roofed concrete firing shelter and a barricade built of railroad ties and filled with sand, sited 30 feet to the north and at an angle to the shelter. The firing shelter was attached to the northeast corner of Building 620 via a wooden ramp. A small addition was built on the east side of Building 620 to serve as an instrument room for the physicists working on the project. In 1944, a 20-foot addition to the instrument room was built on its south side, containing a work room and a metal parts storage room (which later became a camera room). All of the individual rooms of these additions to Building 620 were accessed from the covered wooden walkway. The firing shelter was roofed, and the fenced-in range between the firing shelter and the wood barricade/slug butt was enclosed with upright railroad ties and roofed over in 1954; and at some point a steel plate was added to the barricade.

Building Information

Year Built



Concrete; railroad ties; frame on concrete foundation


Instrument rooms 7'10" x 11' and 7'10" x 20'8"; firing shelter 12' x 24'; barricade 10' x 10'


Addition to instrument room 1944; roofing and enclosure 1954


  • Building 620C Plan

    (click on the image for a separate close-up view)

  • Building 620C Location Plan

    (click on the image for a separate close-up view)

  • Building 620C Addition Plan

    (click on the image for a separate close-up view)

    Note: on this drawing for the 1944 addition, the instrument room was labeled as Building 622


Additional Building Photographs

building No. 620C

From front to back are the 1944 work room, the 1943 instrument room (front gabled), and the concrete firing shelter

building No. 620C

Remains of barricade

building No. 620C

Concrete firing shelter and enclosure to barricade, beneath Picatinny Peak