(Third person pov) (after halo 5 events)
Thank you SirViper for making me want to write this.

Chief was just sitting in his Saber's cockpit when all of a sudden a loud grinding noise came from the slipspace drive when he pressed the button, then he blacked out...

Chief awoke in his ships cockpit, he pressed the nav system and he was in uncharted space. He had tried to turn the engines back on but he had no luck the ship was floating adrift he had no other choice but to activate the ships distress pulser.
(Meanwhile on the bridge of a republic cruiser)

"Sir we are picking up a unknown distress call should we intercept it?"
"Send the probes first we don't know what's out there."
"Yes sir!"
"Sir the probes only list one ship in low power mode."
"Set a course."
"Yes sir."

(Back in Chiefs view)

Chief had noticed that there was a ship coming to help him and he waited for them to arrive...
------------------(2 hours later)-----------
The ship had warped in and had a tractor beam on his ship pulling and aligning the ship for the hangar. Chief turned off the distress pulser and activated the landing gear, he climbed out of the cockpit to find him being swarmed by clones. Then Anakin walked to the middle of the group and asked "Identify yourself?!"
Chief responded "Spartan sierra 117, Master Chief Petty Officer of the UNSC navy." The clones were talking among themselves "what the hell is a spartan"
"Is the UNSC a new faction? If so are you with or facing the Republic?"
"What's the Republic?"
"How long have you been stuck under a rock?" Ahsoka replied walking to see what the commotion was about
"I will let you stay on this ship if you can fight with us."
"Very well."
The clones walked up to him looking at his armor meanwhile Rex was moving them out so he could speak "I'm Sargent Rex" he took his hand out to shake it "it's nice to meet you."
"Likewise, I need a weapon"
"Follow me" Chief followed the soldier to the armory "can you recreate these?"he took the magazine out of his Ma5 and put it on the table
"What are those?" Rex asked
"Projectile bullets."
"Those haven't been used in a long time"
"Then what do you use?"
"Ok, light or heavy?"
"Heavy."
Rex takes a DC-15A rifle off one of the racks and hands it to Chief
"What does it shoot?"
"Charged compressed energy particles."
"That sounds like plasma weapons the covenant uses"
"Covenant?"
"It doesn't matter can I test it out?"
"It has 4 fire modes it fires its normal bolts and its smaller counterparts bolts and allows you to fire 500 shots before reloading,then it has a long range mode which allows semi auto firing capable of 10 km range then you have the armor piercing which allows 10 shots before reloading."
"Ok let me test it."
Rex moves to the range and tells Chief "stand on the platform your test will be at my level so you'll face 500 battle droids 200 super battle droids and 20 destroyer droids"
Chief got in his position and signaled Rex that he was ready
"They shoot back." Rex stated
Chief just stood there waiting to assess the situation gun ready the droids took position and the chamber "Starting in 5 4 3 2 1 go!" Chief took off and started firing his new weapon which was much to his liking,as he killed 10 battle droids with 10 shots of his new DC-15A rifle, he had fought through almost all of droids and was now killing the destroyer droids, he saw the shield around them and he still had some of his grenades from the UNSC and threw a plasma under one as it detonated the droid was destroyed with it then he tried the ap function on his rifle he shot the droid, it took the shield off and stunned the droid he swapped modes and killed it he repeated this to the rest,as he had to reload his weapon
halfway through them he swapped the energy pack and killed the rest then a droid who had survived shot him but the droid didn't know he had a shield and Chief turned to shoot the droid in the head as he walked back to the platform he stepped back out and walked over to rex and asked "how did I do?"
Rex could only respond with awe as no soldier has beaten his time before "you did better than me on the time part but you did get shot but it didn't affect you,why?"
"I have a shield like the destroyer droid it blocks all projectiles coming at me."
"That would save a lot of life's you know"
The intercom came online"Master Chief Please report to the bridge."