Here is documentation about arrow wounds during the Civil War era.
3 September 1863, the Battle of Stone Hill was fought in North Dakota. Corwin Lee: 7th Iowa Cavalry Company M, The Sioux City Cavalry wrote a vivid account of the engagement that was printed in the Iowa City Republican. The full text is on page 263 of
Iowa Valor, a compilation of Civil War Combat Experiences from Soldiers of the State Distinguished as Most Patriotic of the Patriotic.
The Lakota had fought from the cover of a ravine leading to a wetland & lake. As darkness fell, the Lakota who survived retreated from the filed.
"Col. Wilson had his horse shot under him, also the Adutant, who was wounded & lay on the field, covering himself with his robe. During the night he was discovery by an Indian & stabbed with a butcher knife three or four times, the knife being left in a wound. he lived into the next day. In the ravine the Indians' plunder lay, literally covering the ground, showing unmistakable evidence of the severity of our fire. Dead & crippled ponies, squaws, papooses & Indians lay in confusion & blood scattered on all sides."
"During the next day there was considerable running round or the battle field. One wounded Indian was discovered in the grass & with his bow & arrows he succeeded in wounding two of our men before they could kill him. He would shoot tow arrows at a time, & dodge down into the tall grass before they could get a sight of him."
"Our second bugler & the sergeant of the battery brought him down with their revolvers & the bugler scalped him before he ceased kicking."
The Battle of Stone Hill is a state park in North Dakota.
Fetterman was lured into a trap by that the Lakota, Northern Cheyenne & Northern Arapaho had spent weeks to prepare. They called the engagement the Battle of the Hundred in Hand.
Fetterman's death site is location where he & 80 men infantry were brought under attack from two directions. He & his men when down in minutes under a shower of arrows. The attackers inflicted friendly fire casualties on each other.
I highly recommend an article available online from the Journal of the American Revolution. Techniques & Tech/May 16, 2013.
Battle Wounds: Never Pull an Arrow Out of a Body by Hugh T. Harrington.
The most complete & detailed account of arrow wounds & treatments is Dr. Joseph Howland Bill's "Notes on Arrow Wounds" is considered the definitive work on American arrow wounds.
In 1860 Bill was commissioned 1st Lieutenant & assigned to Fort Defiance, New Mexico. There, he wrote a 22-page essay,
"Notes on Arrow Wounds," which was published in
American Journal of Medical Sciences, 1862. He was transferred east, serving in the Civil War & stayed in the army until his death in 1885.
Dr. Bill encountered arrow heads made from stone, antler, shell, hardwood, bone & metal. The arrow head was attached with tendons or sinews. Once wet, the arrowhead would become loose form its contact with blood & other bodily fluids. Attempting to pull the arrow out would leave the head in the wound. The doctor would then have to probe the wound like searching for a bullet.
"...expert bowman can easily discharge six arrows a minute."
In one of Dr. Bill's case studies, three soldiers suffered 42 arrow wounds between them. He also says that he only rarely saw a patient with only a single arrow wound. Because of the ragged edges of the arrow head, leaving it in the wound as could be done with bullets, was not an option. An arrowhead would aggravate the wound & cause inflammation. Only amputation could save the patient.
"We might as well cut the patient's limb up until we do find the arrow-head."
If an arrowhead had lodged in a bone, great effort was required to remove it using a wire loop.
"...bracing my knees against the patients thorax, I applied all the action I could muster. Suddenly the arrowhead flew out of its seat, & I would have fallen on the floor, had not the steward caught me."
Bill observed eighty arrow wounds, the majority to the trunk, thirty six in all. Of these twenty-two died. There were 35 wounds to the extremities. He concluded that arrow wounds were more likely to be fatal than those from bullets. Bill's is the only documented historical report on the nature & treatment of arrow wounds.
<ehistory.freeservers.com> Joseph Howland Bill, M.D., Arrow Wounds & Treatments on the Western Frontier... a fatality greater than that produced by any other weapon. by Lisa A. Ennis & Hugh T. Harrington is a really good capsulation of Bill's book.
The metal identified in arrowheads was almost always taken from a barrel hoop. I haven't encountered any copper or bronze heads. In antiquity they were cast, which wasn't a technique used on the plaines.