Not focused on Company G, but a good account of Gaines' Mill:

“THE EIGHTEENTH GEORGIA REGIMENT.

CAMP, 18TH GA. REG’T, HOOD’S BRIGADE,

25 miles from Richmond, Va.
To the Editor of the Whig:

For the gratification of the relatives and friends of the members of this Regiment, I desire to give a brief account of the particular part enacted by them on Friday, 27th June, in the engagement of Coal Harbor or Gaines’ Mill. Having been with them through the whole action, and taken part with them, your correspondent has perhaps a better opportunity than any one else of knowing exactly what they did. It will be remembered that the fight began early in the afternoon and was raging with great fury while Hood’s Brigade was yet a considerable distance from the scene[,] [m]arching rapidly through the woods and fields, apparently with a view to turn the enemy’s extreme right. The whole Brigade was halted about 4 o’clock and former in line of battle in the following order, 18th Georgia, 1st Texas, 4th Texas, 5th Texas. The position of the 4th Texas was subsequently changed to the right of the 18th; in this order the Brigade advanced through the woods, which being so very thick we soon lost sight of all except our own Regiment. Advancing across a deep muddy swamp, and up a steep ascent, they were placed in position to support a battery and ordered to lay down. Here they were just in range of a heavy battery of the enemy, and the missiles fell so thick that our battery soon became disabled and had to withdraw. Another came but was also compelled to retire after a few rounds. After which, the Regiment was ordered to change position, moving by the right flank at “double quick.” They remained behind this battery about thirty minutes and lost some twenty or thirty men killed and wounded. After marching by the flank for about a half mile, they were halted in an open space to the right of a piece of woods and in the rear of an apple orchard and formed in line of battle. Then advancing under a shower of shot and shell down a long slope which was completely commanded by a body of the enemy’s infantry on their left, posted on a wooded eminence on the opposite side of the ravine at the foot of the slope. Here we lost many more men but passed on without returning the fire of the enemy poured into our ranks, and crossing the ravine at the point where the 4th Texas had so gallantly driven the enemy back, advanced up the steep hill on the opposite side, and here, for the first time, obtained a view of the terrible work that then remained for them to do. Several regiments claim to have taken batteries, and no doubt justly too, for there were enough for all to have a showing. Several of them [batteries] had been taken up to the moment the 18th reached the crest of the hill, but the main battery on the hill in the field, said to be the Hoboken Battery of fourteen splendid brass pieces, which was filling the air with its deadly missiles, and dealing destruction all around, the on whose position [sic] is said to have been chosen by McClellan himself, and whose guns, according to the account of numerous prisoners and wounded men, had been directed by him, was still playing with terrible effect. It was supported by a large body of infantry in the rear, and a detachment of the 2nd Regular Cavalry on the left, besides the approach to it was completely commanded by two other batteries. So admirable was this disposition of the forces and the natural conformation of the ground, that McClellan is said to have assured the men that it was impregnable. In front of the 18th, at the moment it came in sight of the battery, lay a long sloping hill, at the foot of which, some three hundred yards distant, was a deep, and in some places, an impassable ditch, then a quick rise, that afforded some protection from the guns above. Preceding regiments had done their work well, and gallantly had they driven the enemy from some of his strongest works and taken several batteries. Some had even advanced on this battery, but found their forces so much scattered, after crossing the ditch, that they became powerless, and could do little else than seek protection under the crest of the hill from the guns above. Down this first slope the 18th advanced in splendid order, at double quick, under a cross fire from two batteries on the right and left and a terrible direct fire from the battery in front. Shot after shot tore through the ranks, leaving wide gaps, which were quickly closed up; the clear, shrill voices of Major Griffis and Adjt. Patton could be distinctly heard amid the bursting of shells and whistling of shots, coolly commanding, “Close up,” “Dress to the right,” or “left,” while every other officer exerted himself to preserve the line unbroken. Dead and wounded men fell on every side, while the living pushed on to the work before them. Here Lieut. L. A. McCullock, of Company C, Jackson County Volunteers, fell terribly mangled with a shell. Lieut. Sisman, who succeeded him in command of the company, was wounded a few steps further on, Lieut. Callahan taking command of the company. Lieut. John Grant, commanding company H, was also wounded and left, the command devolving on 1st Sergt. Cotton. On reaching the ditch, the line was necessarily broken, the men being compelled to get across as best they could. Advancing a short distance, they found themselves under cover of the hill in company with a detachment of various other regiments who were in a broken and disorganized condition. Some had lost their leaders, some their regiments, and all, for the time being, seemed to have lost their organization. In front of all these the colors of the 18th was [sic] planted, and the men quickly rallied and formed. A short consultation among the officers was held to secure a concert of action, after which, a small detachment of the 11th Mississippi, under the command of Colonel Liddell, formed in support of the right, and another from the 4th Texas, under Captain Townsend, supported the left. Thus supported, at the command “Forward,” the 18th moved steadily up the hill in the very jaws of Death itself! As soon as they were discovered the enemy’s cavalry made a desperate charge at the right wing, which might have broken and ruined the line, had they not been received with so much coolness and deliberation by the gallant men composing Companies A, B and C, commanded respectively by Captains Opal, Stewart and Lieut. Callahan, who held their fire until the enemy were within good range, and then poured in a deadly volley that broke their front, brought down their leader, and so discomforted them that they changed their direction and endeavored to make their escape, but before they succeeded in doing so scores of their saddles were emptied and many a crippled steed left hobbling across the field. Just as this charge was made the left wing had come up within range of the guns, when one of them delivered a volley of grape full into the ranks of Company K, instantly killing Lieutenant Dowten and a man, and wounding half-dozen others. The whole line halted to deliver their fire, which they did so effectually that for a moment the firing of the battery ceased, and the battery began to fall back. Seeing the opportunity, Colonel Ruff ordered the charge, and rushing to the front, hat in hand, waved the boys onward, and, in less time than it takes to write it, nine pieces of the battery were theirs. At this moment, the scene in front was indescribable. Cavalrymen, artillery limbers and caissons and infantry all rushed away in one wild sea of confusion, running for dear life. Some few cannoniers, however, stood to their guns and continued to load – one was shot at the piece while ramming down a cartridge, another, while adjusting a friction primer, was shot down by private Monroe Windsor, of Company H, and his bag of friction primers captured by him. Lieut. Lawes, of Company D, with four men, rushed forward and shot the men at one piece while they were on the eve of firing it. Corporal Foster, of Company F, deserves great credit for the gallantry with which he bore the battle flag to the front – ever foremost. When he reached the battery, he mounted one of the pieces and waved his flag in triumph, but as soon as the regiment was again ordered forward in pursuit of the enemy, he took his place and rushed
on. At this point, Colonel Ruff, seeing that his regiment had pierced the enemy’s lines to a considerable distance, left Major Griffis in command, and stopped to rally stragglers, who were constantly coming up, and turn their fire to the left, whence the enemy was pouring a hot fire on the men about the guns. The regiment followed and drove the enemy about four hundred yards into the woods, when it was thought advisable for them to fall back, as they were entirely unsupported, and had pierced the enemy’s lines about a mile, and there was a considerable body of the enemy in the rear, both on the right and left. Fortunately, our forces drove these back about night, and the 18th held its position for the night, sleeping between the pieces and the enemy. The regiment was under fire for about three hours, and lost one hundred and forty eight in killed and wounded. Two officers killed and six wounded. Carried into action 507 men. Every officer and man acted with great gallantry and coolness. Captain Armstrong, seeing one of the guns aimed at his company, saved them by an oblique movement to the right in double quick. Captain Maddox led his company through the fight, though so badly wounded as to have to retire to the rear immediately after the engagement was over. Lieutenant S. V. Smith, Company K, led his company with great coolness, notwithstanding his loss was very heavy. At the ditch in front of the battery, he found fugitive Yankees so thick that he had to make them get out of his way and allow his men to pass. Lieutenant Hardin, commanding Company F, acted very gallantly. The regiment took about two hundred prisoners; among them one Colonel and several Captains and Lieutenants. The commander of the cavalry that charged our lines and who fell into our hands a wounded prisoner, declared he had as leave charge a wall of fire.

‘CHICKAHOMINIE.’

Macon, Atlanta, Marietta, and Cassville papers please copy.”

Source: Richmond Daily Whig, 10 Jul 62, p. 2, c. 4, 5.