This has been discussed here a number of times. Something similar to what we today call a "short-starter" was used by the US Army at least by 1840. The response below is from 2014. I added the
bold highlighting below.
https://americanlongrifles.org/forum/index.php?topic=32559.msg312499#msg312499Regarding Short Starters:
The British Army Rifle Regiment were equiped with what was referred to as a loading mallet. However, no detail descriptions or instructions for use have ever been found.
Along this same line, I found this regarding a similar device used by the U.S. Army:
Practical Instructions for Military Officers, for the District of Massachusetts, published 1811
Equipment
The balls attached to the cartridges are enclosed in a linen or milled leather patch well saturated with grease; when the powder is emptied into the rifle, the ball is to be separated from the paper, placed upon the muzzle and driven in with a stroke of the mallet, as will be described in the exercise of the rifle.
The bayonet must be slung on the left side, in a scabbard, the belt of which buckles round the waist.
The pouch is worn in front like those of the cavalry, and the belt also buckles round the waist. To this belt a case is fitted for the handle of the mallet, which must hang down the right thigh.
Loading from Cartridge
V. Load! One Compound Motion
Turn up the right hand and shake the powder into the barrel, pressing the cartridge with the thumb and finger, to force out the powder; instantly bring the paper to the mouth and with the teeth separate it from the ball and, patch, which place upon the muzzle, the stitched side up, and instantly slide the left hand to the muzzle and place the fore finger upon the ball; at the same time, with the right hand, grasp the mallet, draw it partly out, and seize the handle.
VI. Drive Ball! One Compound Motion
Bring up the mallet, flipping the finger from the ball, and with one or two strokes drive the ball into the muzzle; with a quick motion,
place the end of the handle upon the ball and grasp it with the thumb and finger of the left hand, and with a few smart strokes upon the mallet with the right hand, drive the ball down the full length of the handle; instantly return the mallet to its sheath and seize the ramrod with the thumb and finger of the same hand, the thumb up.
Loading Loose Ball and Powder
V. Load! One Compound Motion
Pour the powder into the barrel, drop the measure and grasp the rifle with the left hand a little below the right; disengage the right hand, carry it down to the pouch, take out a ball and patch and carry them to the muzzle, place the patch upon the muzzle and the ball upon the patch, flip up the left hand and place the fore finger upon the ball, the other fingers round the muzzle, and with the right seize the mallet as in loading with cartridge.
VI. Drive Ball - As explained in Loading with Cartridge
My guess is that these instructions may well have come from U.S. Officers reading British Army manuals.
I would also question why non of the at approximately 1000 men of just one battalion didn't take the use of this device home when they got out of the Army.
In addition there is a patent issued by the U.S. Patent Office for a false muzzle design.
U.S. Patent, #1565
Alvan Clark
April 24, 1840
Justification
… thus more effectually saving the patch from injury, facilitating the loading, enabling the shooter to load as tight as desirable, and at the same time to dispense with the use of the mallet and stick in loading; and also preserving the barrel from injury and wear.
The implication of the above justification for the patent would indicate that loading mallets and sticks were in sufficient widespread use and that there was value in eliminating the need for their use.
It also makes the case that a fair number of people were using either something similar to a single piece short starter like the military loading mallet or were using a two piece short starting system of a mallet and stick.