After emerging from winter quarters during the early spring of 1864, Coyne and his regiment were reassigned to the 2nd Brigade, 4th Division of the U.S. Army's II Corps from March to May and then re-assigned again in May to the 4th Brigade, 3rd Division within that same Corps. Ordered to duties associated with Lieutenant-General Ulysses S. Grant's Overland Campaign (May 4 – June 24, 1864), they then fought in the battles of the Wilderness (May 5–7), Spotsylvania Court House (May 8–21), North Anna (May 23–26), Totopotomoy Creek (May 28–30), and Cold Harbor (May 31 – June 12), and engaged in the Siege of Petersburg from June 9 until June 22 when the regiment was transported back to New York for muster out and reorganization. Although a number of 70th New York infantrymen were subsequently re-mustered into the 86th New York Infantry, Coyne was honorably mustered out in New York City on July 1, 1864.