I'm having fun with this nerd war against 40K and Halo. Heres the standard weapons of a space Marine and Spartan.
And it's up to you, which is better gun....But before you decide I want you to read what the weapons can do before you decide.
40k Godwyn-Pattern Bolter
The Bolter and its variants are some of the most powerful hand-held weaponry in the Imperium. The Bolter is a weapon synonymous with the Adeptus Astartes, and rightly so. However, although the Space Marines are its primary user, the Bolter finds itself in use in military organizations throughout the Imperium. The weapon is fearsome, with explosive rounds capable of ripping through or blowing apart a foe. The Chaos Space Marines were issued their Legion's bolters before the Horus Heresy, and therefore, use generally older variants than present day Loyalist Space Marines.
The Bolter is a large, .75 calibre assault rifle. It has a much greater mass than most standard-issue rifles. Unlike most rifles, it lacks a stock, resulting in a grip much like a pistol's or a submachine gun's. A Space Marine's bulky power armour would make shouldering a stock an awkward experience, but power armour is most likely also able to compensate for vibrations and oscillation, making a stock redundant. Stocks are sometimes used, however, with an extended barrel and an M40 Targeter System to transform the bolter into a sniping weapon system. These sniper-bolters are most often used with Stalker Silenced Shells.
Standard Bolt: Standard-issue antipersonnel ammunition. Designed to penetrate a target and detonate, causing horrific injuries.
Kraken Penetrator Rounds: Powerful armour-piercing rounds. The deuterium core is replaced by a solid adamantine core and uses a heavier main charge. Upon impact, the outer casing peels away and the high velocity adamantium needle accelerates into the victim, where the larger detonator propels shards of super-hardened metal further into the wound. These are effective against heavily-armored infantry.
Inferno Bolt: Are designed to immolate their targets and destroy them with superheated chemical fire. The deuterium core is replaced with an oxy-phosphorus gel, known as Promethium. However, due to the decreased projectile mass, armour-piercing capabilities are compromised.
Hellfire Bolt: Are designed for use against organic targets. The core and tip are replaced with a vial of mutagenic acid and thousands of needles. When the round enters the target's body, the vial shatters and the needles pierce the victim's flesh, pumping the acid into the target.
Metal Storm Frag shell: The mass-reactive fuse is replaced with a proximity fuse, and the Deuterium Core and Diamantine tip are replaced with increased high-explosives and a fragmentation casing. This means the bolt explodes when it nears an enemy, creating a lethal hail of shrapnel. Capable of inflicting casualties on multiple lightly-armoured targets, but its effectiveness is dramatically reduced when facing heavily-armored foes like Chaos Space Marines.
Stalker Silenced Shells: Are rounds with low sound signatures, meant for covert fighting. They are often used in conjunction with an M40 Targeter System, an extended barrel, and a stock to create a sniping weapon system. A gas cartridge replaces both the propellant base and main charge for silent firing, but this sacrifices muzzle velocity as a result. A solidified mercury slug replaces the mass-reactive warhead for lethality at sub-sonic projectile speed. These rounds are used when stealth
and precision are required.
Halo MA5C Assault Rifle
The MA5C Assault Rifle is an air-cooled, gas-operated, magazine fed weapon designed for automatic fire. The MA5C is the third rifle in the MA5 Series, the workhorse of the UNSC Marine Corps that has been in service for more than 50 years. The MA5C has an attached electronics suite that provides information on rounds remaining in the magazine, compass heading, as well as several other "housekeeping" functions. The rifle performs well in a variety of environments especially given the perceived delicacy of the attached electronics suite. The MA5C Rifle can be outfitted with a number of modifications including sound suppressors, a grenade launcher or a standard issue flashlight. More “exotic” ammunition types, like Shredder Rounds, are available for use, however these modifications are available only by Mission Conditional Requisition (MCR). The MA5C Assault Rifle is easily one of the most versatile weapons in the UNSC’s arsenal. Due to this versatility, the MA5C is complimented by many of the UNSC’s other weapons as either the primary means to a kill or in a secondary role as the fallback weapon. The MA5C Rifle has received technical, as well as physical improvements over the MA5B Assault Rifle that include: a heavier barrel with a 1 in 7 twist; a redesigned cowling to house the electronics suite that reduces weight and increases portability of weapon; and a redesigned handguard which is sturdier and provides a more positive grip. The magazine capacity has been reduced to 32 rounds from the original 60 in the MA5B, and the rifle’s range and accuracy has been substantially improved over its predecessor, making it a more formidable Assault Rifle.
The MA5C Assault Rifle and the MA5B Assault Rifle uses M118 7.62x51mm Armor Piercing, Full Metal Jacket Rounds. These rounds are designed to pierce body armor so the rounds are reasonably large, and are surrounded by a molded jacket of either steel or titanium, which enhances its armor-piercing capabilities. The round might also have a carbide or similar hardened tip, and might also be coated in copper or another metal over the steel, titanium, etc. shell. Actual energy from this round is 2472 ft·lb force. This is quite high for a rifle cartridge, and the round has been historically noted for its power and range. "7.62mm" is the diameter of the bullet itself, which equates to 0.3 inches, or .30 caliber. The "51mm" comes from the length of the bullet. Often being associated with a considerable amount of recoil, the MA5C appears to be able to absorb it so the weapon remains steady even during cyclic fire. Armor-piercing rounds have the obvious advantage of being able to deal with protected targets, but instead of causing larger wound channels by tumbling like lower-caliber ball or non-jacketed munitions, AP rounds have a tendency to over-penetrate the body, causing less overall trauma.