JK Rowling owns all this. I'm just repurposing the characters.
Be courteous to all, but intimate with few, and let those few be well tried before you give them your confidence.
True friendship is a plant of slow growth, and must undergo and withstand the shocks of adversity before it is entitled to the appellation.
Five year old Draco Malfoy opened the door to his father's study, concealing the nervousness that he felt.
"Ah, yes," said Lucius. "Gentlemen, this is my son Draco. Draco, these are my associates Mr. Nott, Mr. Crabbe, and Mr. Goyle. These young men are their sons: Theodore, Vincent, and Gregory. They have come to join you for your special lessons."
Lucius motioned for Draco to join the other boys, and then he began to teach the assembled group - their fathers watching with curiosity. "Do you know what the highest form of life is?" When he saw that only Draco was ready to answer, Lucius motioned to him.
"The human being," Draco answered.
"That is correct my son. And could you tell your new friends what is the highest form of human being?"
"The wizard," Draco replied.
"And what is the highest form of wizard?"
Draco replied with increased confidence: "Those of pure blood."
Lucius smiled at his son. "That is correct Draco. You boys would do well to remember that. Those of us of pure blood are indeed the highest form of wizard. However, we cannot afford to ignore those of lesser blood. Though they do not have the purity that we do, they may still have intelligence and even power.
"You must not also forget that Muggles have themselves invented fiendishly clever weapons, creatures of mud though they are. Nor should you underestimate such creatures as goblins, elves, and centaurs. They too have power."
Lucius paused to allow the boys to consider his instruction before calling out to one of his house-elves: "Dobby!"
The miserable creature appeared, wringing his ears.
"Dobby," Lucius said, "I wish you to locate a Muggle military base and then to procure for me an example of the Muggle weapon known as an 'automatic rifle.' Make sure it is fully loaded with its..." he sneered, "Ammunition. Now!"
The elf popped out of the room and within less than a minute it returned with an oddly shaped black object which he handed to his Master.
"Gentlemen, in an effort to understand the creatures that we must control, I have made somewhat of a study of these Muggle weapons. I wish you to view the devastation that Muggle weapons can produce."
Lucius turned toward a wall that was covered with paintings. He checked the safety, flipped it to fully automatic fire, placed the stock to his shoulder, took aim at a painting, and squeezed the trigger.
The only being in the room that was not surprised by the sudden outburst of noise and destruction was Lucius himself.
Lucius set the rifle down on a table and then addressed his guests. "Gentlemen, you see while not as destructive or as powerful as magic is capable of being, this device is certainly capable of inflicting plenty of devastation.
"Dobby, repair that damage and then take this rifle back to where you got it. After that, you may return to your normal duties"
In a few short moments, the elf was gone and the room looked as though nothing had happened.
Lucius now turned to address only the boys. "You also see here the power of the lowly house-elf. While it is right and proper that they serve us, we must never forget that they do possess tremendous power. We may use their power to our benefit, but we must never forget that it is there.
"I wish you boys to understand something. You must never underestimate your opponent. Even those who are of lower ability than you are may still catch you by surprise if you underestimate them."
The boys nodded their understanding.
"Now," Lucius said, "You will be coming over here for the foreseeable future one day per week so that I may give you special instruction in an area of particular expertise that I have.
"You see, my young wizards, not every wizard understands the truth of the superiority of the pure-blood wizard. There are those within our community who would seek to elevate mudbloods to equal status with us. There are even some of pure blood who agree with that despicable sentiment.
"Unfortunately for our just cause, those individuals are currently occupying positions of power thanks to the Potter infant and his defeat of the Dark Lord. Therefore, those of us who know the truth must tread cautiously. We must move among them, pretending to be them, pretending to agree with them. We must publically repudiate that which we know to be true. This is why you must learn the Art of Deception.
"You must understand this from the beginning: you cannot hope to fool me. I have studied this art since long before you were born and have been its master for many years. You would be wise to learn that you cannot use what I teach you against me. You should also take care not to use it against any who support our cause. Against the mudbloods, the Muggles, and their blood traitor allies, however, it will make the most potent weapon."
Draco Malfoy returned to his room smiling. His father was giving him special lessons that would help his overcome the mudblood filth. He was so excited.
"Dobby," the Malfoy heir called.
The elf appeared. "What does young Master desire?"
Draco sneered at the creature before him. "Bring me one of those rifles that you brought Father."
"Dobby apologizes," the elf whimpered, "but Master ordered Dobby to not bring one of those to young Master."
Draco kicked the elf. "Get out of my sight! Go punish yourself."
With a sob, the pitiful elf disappeared.
In a secret passage next to Draco's room, Lucius watched the scene that had just unfolded. He shook his head. Draco had much to learn about self-control. He had known that Draco wouldn't be able to resist the Muggle weapon and had previously instructed all the house-elves not to retrieve such things for his son. In addition, Draco's temper would need to be controlled. Otherwise, it might become something that could damage Lucius' plans. There was much work to be done.
There you have it. In case you hadn't guessed, this is not one of those stories where Draco is a nice guy. There are no "leather pants" here. I do have a good!Draco story and an antihero!Draco story in the works, but no promises on when.
We'll have a bit of the original timeline before the time travel occurs. Once Harry does his Peggy-Sue (that's mental time travel into your younger body for those who don't know the term) you might appreciate the background info because this will not be the standard method of memory transfer.
Regarding the rifle Lucius uses… I got the mental image of Lucius firing a select-fire rifle on full auto and knew I had to use it. According to what I could research, during the 1980s, the British military used some of the different variations on the AR-15/M16 family of rifles in 5.56x45mm NATO. I picture Lucius with an M16A1 with a 30 round magazine, but imagine whatever you want.