Well this is an excellent thread with much useful information.
I can add that some breechloaders and repeaters were issued with a chamber, and I suppose throat, cleaning tool to be used in thefield when fouling began to build up enough to hamper loading. The tool was shaped like a chambering reamer only made from bronze rather than steel.
water was poured through the bore from the open breech and the tool inserted and given a few turns to scrape away fouling.
The British at Isandwana discovered to their misfortune that the Martini Henry rifles could begin to jam after two dozen or so volleys. They'd began firing at extreme range so by the time the Zulu closed to close quarters most of the muskets were already out of action or so badly fouled that reloading was difficult.
This left them facing born and bred spearmen with bayonets, the British were outclassed in such close quarter combat.
A test using Martini Henry rifles and period style ammo in a testing chamber in which the known humidity and temperature of that day was reproduced confirmed that report.
As for the arrow heads, the site of the last stand of the Spartans had been subject of debate due to lack of there being any large number of arrowheads at the site, but a few years ago excavation of a nearby well uncovered thousands of arrowheads.
Its very likely that the bodies of the Spartan warriors were chopped up and thrown down the well, a not uncommon practice in those days and one which Native American war parties are known to have followed in colonial times.
Scavenging battlefields for any bit of metal was a common practice in ancient times, and is still practiced in the Middle East.
An entire nation of nomadic scrap metal scavengers was known to roam the battlefields of the Middle East, which is why so few metal artifacts can be found to confirm ancient records of great battles.
Indians couldn't just stop at a outdoor supply store to pick up a fresh pack of broadheads, they scavenged every arrow and arrowhead they could, it would be more suprising if there had been many arrowheads found there even a day later much less a century or more.
A common Plains Indian steel arrowhead was actually a small scrapper blade once used to scrape away ink from a page so the paper could be reused. The blades were common and cheap and merchants found they could sell them by the bushel to the Indians.
Mutilated bodies were sometimes the result of a warior cutting out an arrowhead or even to recover bullets to be melted and recast, or just hammered back in good enough shape to fit down the bore of a muzzleloader.
Other supposed mutilations would be easy for a Homicide investiigator to recognise as defensive wounds. indians seldom wasted much time cutting up someone once they were dead, but people take a lot of killing when knives and hatchets are the only tool at hand.
There were of course some specific ritual mutilations like scalping or cutting off a hand. The Zulu split a body open to release the spirit, they believed the swelling up of a decomposing body was the spirit trying to get out, splitting the body was actually a sign of respect for the fallen enemy, they didn't bother to do so if they held the fallen in contempt.
As for Colt grip screws. Complete disassembly for a through cleaning was common, so screws were made of fairly soft steel. Its a lot easier to replace worn screws than to rethread worn screw holes.
The threads of my replica colt wore quickly and often backed out under recoil. I replaced these with some identical screws I found at at an old Singer Sewing machine repair shop. So far the replacement screws have given no problems and don't shoot loose.
A side note is that some quick draw artists found that they could draw a colt so fast that they sheared off the grip frame screws, leaving them holding a grip but no gun. Pistols modified for exhibition fast draw sometimes use special hardened oversized grip frame screws.