One hundred yards away you can’t tell these guns from the real thing - except that they don't shoot at vou. The 104th Ordnance company has been building dummy 37-millimeter antitank guns for the 29th Division at Fort Meade, Md. The machine work is done in the army repair trucks. Acetylene torches and electric welders are used in assembling the dummy guns from old automobile and truck wheel and axle assemblies and other junk parts.