Author's note: so i know I've been bouncing back and forth between a T rating and an M rating and the reason for that was because I always considered my story to be a hard T or a soft M because so far most of the content has been relatively mild except for my language in the description and even that is toned down for me. That's changing because I'm going to be taking the story in a darker direction and the latest mini chapter I'm putting up is going to be set over a decade into the Reaper war.
Spartan-117 woke up with a massive headache. At least he wasn't dead. Despite telling Cortana otherwise, he didn't expect to make it when the Halo fired. Then a voice called to him, it was faint as if he were underwater. He shook his head clear, it helped a little bit. He could make out words now. "Chief! Can you hear me?" Cortana was pleading now. The Master Chief turned on his helmet lights, a single beam of light in the darkness. It was then that he realized that he was floating. So the gravity was out, at least temporarily. Lovely.
"I thought I'd lost you too," Cortana said as he floated towards her. Years of training had taught him to move with perfect precision and grace that would make a dancer envious. It was necessary when operating in zero-gravity.
"What happened?" He asked.
"I'm not sure," his AI companion replied. Well that's a first. "When Halo fired, it shook itself to pieces… did a number on the Ark. The portal couldn't contain itself. We made it through just as it collapsed." John looked around at the wreckage. "Some of us made it." The Forward Unto Dawn had been cut in half by the Slip-Space portal. The Spartan floated from room to room searching for their Sangheili companion.
"The Arbiter?" he asked. The Master Chief was already sure of the answer. Cortana shook her head. He moved towards the cryo bay.
"But you did it. Truth and the Covenant… the Flood… It's finished." She said it with a strange mixture of hope and sadness that the Master Chief had never heard from her before. At least it was an improvement from how he had found her on High Charity.
"It's finished," he agreed. The Spartan entered a cryo pod and tucked his beaten assault rifle into the rack by the tube.
"I'll drop a beacon, but it will be a while before anyone finds us... years even." The Master Chief nodded as he entered the cryo pod.
"I'll miss you," she said, her voice breaking. Is she malfunctioning?
"Wake me, when you need me." The Master Chief had been at war for as long as he could remember. He could use a break until they were found. The last few months had finally caught up to him and he was exhausted.
Before I get into the actual story, I want to put out some of the technical specs to the weapons to justify how things work out in the plot. This mostly involves changes to the weapons of both Halo and Mass Effect in order to find some kind of balance between the two.
Note: Master Chief in this story will resemble the Book version (specifically the Fall of Reach and First Strike) more than the games. In the books, he's quiet but witty and very intelligent in addition to being an incredibly fast, inhumanly accurate, walking tank. I'm not trying to make him completely overshadow the Normandy crew though.
I took the only measurable feat of a Spartan II in MJOLNIR Mark VI Powered Assault Armor. The Master Chief surviving freefall at terminal velocity twice. While I can't calculate the mass or gravity of Requiem, we do know the gravity and terminal velocity of a human on earth. 9.8m/s^2 and 53m/s respectively. The Master Chief is said to weigh half of a ton in his armor. ½ 500kg*(53m/s)^2=702250. In both instances, the Master Chief survived, the armor was uncompromised but his shields were overloaded and he had a concussion (we know this because he was knocked unconscious).
Freefall and bullet wounds are completely different animals when it comes to killing people. With good shot placement, a .22 is perfectly capable of killing a human being despite only having 100-200 ft*lbf (approximately 140-280J for those in communist countries) on the other hand, a 200 pound man getting thrown on the floor can have more energy but the worst he'll suffer is a bruised ego and maybe some real bruises. Unfortunately this is the only feat that I can actually calculate because of the gameplay vs lore discrepancies.
Again I'm going to have to assume some things. MJOLNIR is described as not being able to withstand many plasma bolts compared to the energy shields so I'm going to say the energy shields provide 75% of the total defenses while the armor makes up the other 25%. Since the armor was uncompromised, I'll say that the energy required to kill a Spartan in MJOLNIR Mark VI is 750000 J or 553171 ft*lbf for free countries. That's a huge amount compared to my previous estimate of about 103000J based on numbers that were basically pulled out of my ass. However it is still lower than the 15MJ on the wiki but the wiki doesn't cite a source. If I go with 15MJ then things go bad real fast.
Why are things bad if a Spartan's energy shield is so powerful? Well it means that an MA5C as described in canon, firing a 175 grain FMJ-AP round at 2790 feet per second should take 164 rounds just to take down the energy shields. Awesome, right? No, not really. Guess who else has energy shields? I'll give you a hint, we haven't been able to play as them since Halo: Reach. A Sanghieli is supposed to have shields about equal to if not slightly stronger than a Spartan in Mark VI armor. They are nigh indestructible to your average grunt. Grunt here meaning infantryman, not an Unggoy.
Now I don't know how the UNSC runs things but if humanity were facing extinction, I'd be fighting dirty to win. Whatever the costs. Geneva/Hague conventions and bleeding hearts need not apply. I get that the Spartans get special weaponry (according to The Fall of Reach anyway) but wars aren't won by those guys alone. They're won by logistics and maneuver and blood. They're won with combined arms and mixed unit tactics. They're won by an 03xx (Marines) or an 11x (Army) taking the fight to the enemy. At the end of the day, the entire Marine Corps works for the 0311 lance corporal and the Army works for the 11B specialist but they can't do their job if their main weapon is incapable of killing the enemy.
In order to fix this, I'm going back and re-calculating all of the UNSC weapons.
Weapon changes to Halo Canon
I made some changes to the weapons in the Halo universe for a few reasons. First, I made the weapon balance more realistic compared to real world weapons.
MA5 series assault rifles: The MA5 series is all over the map when it comes to damage so in order to reflect that, I've changed the barrel lengths between models. Second, there is no reason for a different model of the same weapon to be incompatible with the other's magazines so I came up with an in-universe explanation why the MA5B had a 60-round magazine while every subsequent model had a 32-round magazine until Halo 5. Also you may notice that the assault rifles now have a scope, that's because I figured the Smart-Link can fail sometimes, especially if somebody loses a helmet so you need backup sights similar to how in the real world the military uses an ACOG or an EOTECH/Aimpoint and has backup iron sights
All variants are closed bolt, direct impingement, magazine fed, shoulder fired, forward ejecting bullpup, select fire rifles that have a rail system for mounting a grenade launcher, laser sights etc.
32-round and 36-round magazines witch have consistently proven more reliable than 60-round magazines which were phased out
Are chambered in 150 grain MK211A2 7.62x51mm NATO High Explosive Armor Piercing Incendiary rounds
Equipped with a 4x self-illuminating scope with a Bullet Drop Compensator out to 800 yards as a backup sight in case the Smart-link fails
MA5K has a "carbine length" 16 inch barrel and 26 inch overall length
9 lbs 3000 fps 3000 ft*lbf
MA5B has a "mid length" 20-inch barrel and 30-inch overall length
10.5 lbs 3200 fps 3410 ft*lbf
MA5C has a "full length" 25-inch barrel and 35-inch overall length
12 lbs 3600 fps 4315 ft*lbf
MA5C DMR same as above but with a 3-6-9x variable power scope instead of the Elcan Spectre/ ACOG clone on the others.
MA5D has a "extended length" 30-inch heavy profile barrel and 40-inch overall length
15 lbs 3800 fps 4809 ft*lbf
MA5D DMR same as above but with a 3-6-9x variable power scope instead of the Elcan Spectre/ ACOG clone on the others.
Squad Automatic Weapon
Open bolt, belt fed, air cooled, long stroke piston operated, quick change barrel system chambered in 7.62x51mm NATO. Cyclic rate of 600 rpm
Equipped with a 6x self illuminating scope with a BDC and a RMR sight
20 lbs 3800 fps 4809 ft*lbf
BR55HB battle rifle: I've reduced the Battle Rifle's magazine capacity because it makes zero sense for a battle rifle to have higher capacity than an assault rifle, especially if they're using short fat rounds like they do in the games but I'm changing the caliber because it just makes more sense to use the same caliber projectile to ease the logistics like they would have to in a war for survival.
All variants are closed bolt, direct impingement, magazine fed, shoulder fired, forward ejecting bullpup, select fire rifles that have a rail system for mounting a grenade launcher, laser sights etc
Chambered in M634 7.62x63mm 165 grain Semi Armor Piercing, High Explosive projectile at 3817 fps out of a 25-inch barrel 5317 ft*lbf
Equipped with a 6x self-illuminating scope with a Bullet Drop Compensator out to 1250 yards
24-round magazine
M39X series Anti Personnel Rifle: This one stumped me for a while about whether to make it act like an actual Designated Marksman Rifle as the US military uses the term, or treat it as an antipersonnel sniper rifle while the SRS-99 acts like an anti-material sniper rifle similar to the actual game mechanics. I decided to go with the latter so the DMR no longer uses the same ammunition as the MA5 series assault rifle so it's not a DMR; now the M392 uses a much bigger round that hits harder than both the battle rifle and the assault rifle like it does in the games. This is similar to how the US military has anti personnel sniper systems that are chambered in .300 Win mag or .338 Lapua magnum and also has anti material sniper systems chambered in .50 BMG
Closed Bolt, semi auto only, direct impingement, reversible side ejecting, bullpup with a 10x self-illuminating mil-dot scope
.300 Remington Ultra Magnum 220-grain open tip match projectile 3853 feet per second 7251 ft*lbf or
110-grain depleted uranium Saboted light armor penetrator at 5350 feet per second 7000 ft*lbf
M6 series pistols: It doesn't make sense for a sidearm to be as powerful as a rifle so I've toned it down compared to the rifles however, it's still much more powerful than the real world counterpart Desert Eagle.
12.7x30mm SAPHE 310-grain projectiles at 1881 feet per second 2435 ft*lbf
8 to 12 round magazines
M6J Carbine: Details on the M6J are practically nonexistent so I'm making them up as I go. The only thing it says is that it's a select fire M6 with a 355mm barrel with an electroless nickel finish which extends barrel life. In this story, the M6J has an integrally suppressed free floating barrel with a rail system to attach an optic and iron sights as well as an IR laser.
12.7x30mm 500-grain FMJ depleted uranium projectile 1120 feet per second 1392 ft*lbf
12.7x30mm 310-grain SAPHE projectiles at 2576 feet per second 4565 ft*lbf
20 and 30 round magazines designed for use with M6J but compatible with all M6 series models
M7/Caseless personal defense weapon: The M7 in the game this thing is lethal at close range. In canon, it fires a tiny peashooter moving only a little bit faster than most handgun rounds do in the real world and I will just not accept that for a military weapon five hundred years in the future so I basically turned it into a more powerful P90 with the same capacity as the SMG in the games. Even upgrading this bastard to the 5.7x28mm round and multiplying the KE by 1.6 like everything else, there's no way it should stand up to anything else in the Halo Universe. This thing puts out a measly 672 ft*lbf per shot compared to the Assault Rifle's 4000 ft*lbf. I could upgrade it to a 5.56x45mm NATO round but that would lessen the capacity and seem like I'm making the UNSC seem too badass compared to the Mass Effect Universe. I promise that's not what I'm trying to do here. Also, the M7S from Halo 3: ODST will not be making an appearance because in order to make a weapon "silent", you have to capture the expanding gases (that's what the suppressor is for) and the bullet has to be subsonic so that the loud crack from the sonic boom doesn't get heard. That can work with regular submachine guns because subsonic pistol calibers are generally 125-230 grains which are twice the size of a rifle bullet so it can still do some damage against a human. Pistol calibers would be useless against a Sanghieli. If we take a 55-grain 5.7 bullet which is the heaviest that I know of and shoot it at 1100 feet per second (speed of sound is roughly 1125 feet per second so we're cutting it as close as possible), we have 148 ft*lbf. That's essentially a .22 long rifle with a better ballistic coefficient meaning it will fly a little bit further before hitting the ground and might do some damage to soft tissue. If we say that the UNSC makes these bullets out of depleted uranium, then we have a 92.62 grain bullet and 249 ft*lbs which is still .22 long rifle energy. The UNSC would be better off using the M6J carbine. In fact, I may go back and actually replace the M7 with the M6J because it makes more sense from a lethality and a logistics perspective.
10-inch barrel
5.7x28mm caseless 31-grain full metal jacket rounds at 3125 feet per second 672 ft*lbf
Downward ejecting bullpup
60-round magazine
Folding foregrip
Rail system to mount a scope and/or laser sights
M90 Close Assault Weapons System: I turned the shotgun into a bullpup because it's meant for CQB but it's basically the only gun in the game to be a standard configuration making it horrible for the job.
Soellkraft 8-gauge 4" shells 0000 buckshot 8000 ft*lbf of energy at the muzzle
8-round capacity (4" shells) to 12 (3.5" shells)
24-inch barrel
Bullpup configuration
SRS-99 Anti-Material Sniper rifle: I didn't really do anything to the Sniper Rifle except for the zoom magnification because it's just about perfect the way it is.
40-inch barrel
14.5x114mm MK211 1026-grain High Explosive Armor Piercing Incendiary rounds at 4175 feet per second 39703 ft*lbf or:
230-grain Saboted Light Armor Penetrator at 8000 feet per second 32679 ft*lbf
Four round magazine
Folding Bipod
5-10-20x variable power mil-dot scope
Bullpup configuration
M-41 Surface-to-Surface Rocket Medium Anti-Vehicle/Assault weapon (SPNKR): The only change I made to the SPNKR was giving it the ability to do things that the US military has been able to do for decades.
102mm High-Explosive Anti-Tank Shaped Charge
5x scope with thermal and night vision capabilities
Rockets equipped with Radar and thermal tracking
Mass Effect Weapons
I'm making some pretty big assumptions here since we don't have hard numbers to go on. If you look at the description for weapons in the game, it makes very little sense. If you take a tiny piece of metal and temporarily lighten it using a Mass Effect field in order to accelerate it, conservation of momentum (M1V1=M2V2) says that the object should slow way the fuck down as soon as they leave the mass effect field (the barrel). If you do the opposite and increase the mass then they would accelerate fast as fuck when they leave the barrel. The problem here is that using too small of a projectile moving too fast means that it's going to be turning into plasma and dissipating really fast so in my personal head canon, they're still going with the Small Caliber, High Velocity concept but nowhere near the extent implied by the codex.
If anyone reading this can think of a counter argument that would make more sense, I'm happy to discuss it. Also, I am well aware that there is more to killing power than kinetic energy but that is a very complex subject that is still a matter of debate today.
Now why are the UNSC weapons more powerful than their Mass Effect counterparts? Because the UNSC has a four hundred year head start and the UNSC likes big bore, heavy recoiling, heavy hitting weapons. No, seriously, find an M14 and try controlling that bad boy on full auto. A pistol grip and foregrip won't make much difference because it has twice the kinetic energy and almost three times the recoil of an M16. That's what they consider an intermediate cartridge.
Because of the massive boost I had to give UNSC weapons to stand against the Covenant, I'm also boosting the Mass Effect universe from my previous calculations, though not as much. Also, in this universe, thermal clips have always been a thing and after the Battle of the Citadel, they took heat sink technology from the Geth so during the events of ME2 & 3 they use a combination of the two so that if you fire rapidly, you have to eject a thermal clip and put in a new one but if you fire carefully aimed shots, you're good.
For those interested, the math used was x*y=X*Y, x*y^2/450435= 2.4*(X*Y^2/450435) where x=mass in grains, X=ME mass in grains, y=velocity in feet per second, Y=ME velocity in feet per second.
Assault Rifles
M-8 Avenger
I'm not really sure what backwards military the Systems Alliance is based on but I reasoned that the Avenger would be the future equivalent of the M4 carbine, the standard service rifle of the US Army and possibly the USMC soon (though the USMC adopted the IAR-27/HK416/M27 as the standard service rife which is a very similar weapon but more accurate and supposedly more reliable, the merits of which I won't be getting into).
M4 carbine 5.56x45mm NATO M855 ball, 14.5" barrel 62-grains at 2900 fps 1214.15 ft*lbf
M-8 Avenger .172 caliber 25 grains at 7300 feet per second 2914 ft*lbf
M-15 Vindicator
I made the Vindicator the future equivalent of the M16A4 partially because it shares the three-round burst function and because it hits just a little bit harder than the Avenger like the M16 does compared to the M4
M16A4 5.56x45mm NATO M855 ball, 20" barrel 62-grains at 3100 fps 1331.3 ft*lbf
.172 caliber 25 grains 8002 feet per second 3194 ft*lbs
M-76 Revenant
Shot for shot, the Revenant doesn't hit much harder than the Avenger or Vindicator but has a high rate of fire and large capacity, just like a LMG/SAW should
M249 5.56x45mm NATO M855 ball, 21" barrel 62-grains at 3200 feet per second 1409.5 ft*lbf
.172 caliber 25 grains at 8475 feet per second 3383 ft*lbf
M-96 Mattock
The Mattock is the equivalent of an AR-15 chambered in 6.8 SPC or an AK in 7.62x39mm because it's a heavier hitting bullet but not quite a battle rifle
6.8 SPC II 20-inch barrel 104.6 grains at 2867 feet per second 1909 ft*lbf (For this one I took the average projectile weights and velocities out of a 20-inch barrel because it doesn't have military ball ammo)
.224 caliber 44 grains 6882 feet per second 4582 ft*lbf
Phaeston
The Turians are loosely based on the USSR (they actually resemble the Prussians more but those guys never made it into the modern era of warfare) and in Mass Effect 3, the Phaeston does slightly more damage per shot than the Avenger. Also, according to the conversation with Garrus regarding L2 implants in the first game, the Turians wouldn't lose effectiveness by making things easier on themselves; they wouldn't seek to reduce recoil and switch to a smaller round but rather to master it. Given the above, I've decided that the Phaeston would probably be the equivalent of an AKM.
AKM 7.62x39mm M45 16.3" barrel 123-grains, 2421 ft/s, 1607 ft*lbf
.22 caliber projectile weighing 54 grains at 5834 feet per second 3857 ft*lbf
Athame
Athame is the Asari goddess of prophecy and fate, and the matriarch of the ancient Asari pantheon. This assault rifle is typical of Asari, very precise, lightweight, and with a high rate of fire but not as powerful as its Turian or Human counterpart. I found it weird that Samara would be carrying an Avenger despite limited contact with humans or non-Asari in general so I looked at the wiki only to find that there are no Asari assault rifles in ME3 either with the possible exception of the Chakram launcher so I had to make one up. The AN-94 is a Russian assault rifle that was designed as a potential replacement to the AK-74. However it has a very complex design so it will probably never become standard issue. The advantage of the AN-94 system is its ability to delay the recoil force until the fired rounds have left the barrel. This, it is claimed, enables more 'hits' on target under the most adverse combat conditions. The AN-94 offers a unique two-shot burst function at a stated 1800 rounds per minute rate of fire. The Nikonov mechanism fires the second shot in the burst quickly enough to allow it to escape before the recoil of the first shot is felt, thus potentially allowing the two shots to hit extremely close together, for example to aid in piercing body armor. It's too complex for your average grunt but it would be perfect for an Asari Justicar, as they're the love child of Special Forces and Lone Vigilantes who need to adapt to any situation and would be willing to put in the work necessary to maintain their weapon.
AN-94 5.45x39mm 16.3" barrel 57-grains, 2900 fps, 1078 ft*lbf
.183 caliber projectile weighing 23 grains 7051 feet per second 2587 ft*lbf
Sniper rifles
M-92 Mantis
It was a toss-up between making it the common .300 Winchester Magnum which is the standard sniper round in the US armed forces or the .338 LM. I decided to go for the latter because of how much more powerful it is than the Viper as well as the fact that, like the .338 Lapua magnum, it can be used in an anti material role in a pinch.
.338 Lapua Magnum 300-grains at 2750 feet per second 5020 ft*lbf
.264 caliber 125 grains 6578 feet per second 12048 ft*lbf
M-97 Viper
When compared to the Mantis and especially the Widow, this thing hits really soft. I figure making it the future equivalent to the .308 Winchester/7.62x51mm NATO round was apt. This thing works more like a battle rifle than a true sniper rifle when you consider the large capacity and relatively low stopping power compared to the Mantis.
.308 Winchester 175-grains 2645 feet per second 2720 ft*lbf
.224 caliber 73 grains 6352 feet per second 6528 ft*lbf
M-98 Widow
The Widow is less of an antipersonnel sniper rifle and more of an anti-material rifle which is described in-game as having too much recoil for most people to handle so I decided that a 20mm shell should work.
20x110mm RT-20 2006-grains at 2789 feet per second 34638 ft*lbf
.50 caliber 863 grains 6693 feet per second 83131 ft*lbf
M-29 Incisor
I consider the Incisor less of a sniper rifle and more of a Designated Marksman Rifle or a Special Purpose rifle because of its absurdly low damage per shot (for the class of weapon) but it does fire in three-round bursts so it does more damage per trigger pull than the Viper like how three 5.56 rounds will do more damage than a 7.62 NATO round
MK 12 SPR 5.56x45mm NATO MK 262 Mod 1 20" barrel 77-grains at 2870 feet per second 1409.5 ft*lbf
.172 caliber 32 grains 6895 feet per second 3382 ft*lbf
Submachine Guns: The poor man's assault rifle. All numbers are for an 8 inch barrel
M-4 Shuriken
The weakest of the three submachine guns in the game uses the weakest of the three common pistol calibers.
9x19mm Parabellum 124-grains at 1329 feet per second 486 ft*lbf
.25 caliber 52 grains at 3188 feet per second 1166 ft*lbf
M-9 Tempest
.45 Super instead of .45 ACP because while the .45 ACP is great, it's a little outdated.
230 grains 1249 feet per second 797 ft*lbf
.355 caliber 96 grains 2999 feet per second 1913 ft*lbf
M-12 Locust
A jack of all trades that isn't particularly good at anything just like the .40 S&W
.40 S&W Submachine gun 165 grains 1293 fps 612 ft*lbf
.313 caliber 69 grains 3150 fps 1378 ft*lbf
Shotguns: This is self explanatory. In real life there are three common 12-gauge shell lengths so I gave the shortest to the weakest of the three normal shotguns to the weakest and so on.
M-27 Scimitar
12-gauge 2.75" shells 2935 ft*lbs
7044 ft*lbf
M-23 Katana
12-gauge 3" shells 3202 ft*lbs
7685 ft*lbf
M-22 Eviscerator
12-gauge 3.5" shells 3735 ft*lbs
8964 ft*lbf
M-300 Claymore
Lore describes the Claymore as being ridiculously overpowered and with arm-breaking recoil. In-game it's strong but nowhere near strong enough to justify the single-shot capacity. Fuck that noise. This thing is going to be as ridiculously powerful as the codex tells us it is.
3-gauge 5.5" shells 15144 ft*lbf (estimated based on a scaled up 12-gauge 3.5" shell)
36346 ft*lbf
Heavy Pistols: Mass Effect 2 & 3 go out of their way to call the sidearms Heavy Pistols and they hit harder than the SMGs do (I know that it could simply be game mechanics but I'm assuming otherwise for now). To represent this, I'm going to say that they use the stronger auto-loading calibers. All numbers for a 5 inch barrel
M-3 Predator
10mm is possibly the perfect pistol cartridge with its versatility. This bad boy can be used effectively against all kinds of predators, both two-legged and four-legged. Sadly, the FBI decided it was too stout for their effeminate wrists and down loaded it until Smith and Wesson came out with the .40 Short and Weak because of all the unused space left in the casing. You'll often find that factory loads are fairly tame. Only a few manufacturers offer real 10mm auto.
10mm Auto 180-grains at 1386 feet per second 768 ft*lbf
.312 caliber 75 grains 3328 feet per second 1843 ft*lbf
M-6 Carnifex Hand Cannon
.40 super is the even bigger brother to the 10mm. It's got too much recoil for most people to handle but with proper shot placement, it can stop most North American animals dead in their tracks. Fun fact, at one point it was called the .40 Sig because it has very similar design principles to the .357 Sig
.40 Super 180-grains at 1558 feet per second 971 ft*lbf
.312 caliber 75 grains 3742 feet per second 2330 ft*lbf
M-5 Phalanx
In ME2, the Phalanx was stronger than the Carnifex but in ME3 it was weaker, since this story is mostly taking place in the former, I'm going with stronger and the .460 Rowland packs .44 magnum stopping power in a semiautomatic pistol. Why? Because fuck you, fuck your cover, fuck the two guys behind you, and fuck my wrists that's why. I consider the weaker stopping power in 3 to be similar to going from .460 to .45 Super. Still a strong cartridge but it doesn't even make .40 Super or 10mm kinetic energy levels. On a side note, you are perfectly capable of firing .45 Super or even .45 ACP out of a .460 Rowland. However do not fire a .460 Rowland out of anything except for a firearm specifically designed for it. Unless you don't like your hands.
.460 Rowland 255-grains at 1342 feet per seconds 1019 ft*lbf
.355 caliber 106 grains 3219 feet per second 2446 ft*lbf
The M-8 Avenger has a rate of fire of 850 rounds/minute and takes about 1.2 seconds of sustained fire to take down Shepard's shields in Insanity which is 17 rounds for a total of 49538 or round it up to 50000 ft*lbf if my previous assumptions were anywhere near the ballpark (again, lack of hard numbers make this a pain). Cerberus has a lot of highly advanced technology so if we say that is the "normal" shield strength and Shepard and his team get shields 50% stronger than normal from their nefarious buddies, we can say that Shepard and co. have 75000 ft*lbf shield strength. That's not weak by any means. That's strong enough to take 5 modern day .50 BMG rounds and still not collapse. Remember that the Master Chief's shields were reverse engineered from Covenant technology which in turn was reverse engineered from Forerunner technology. Forerunners make the Reapers look like kindergarteners.
Also, the Mass Effect weapons will perform better against armor while conventional weapons will perform better against shields and flesh. This is inline with current ballistics studies to my knowledge. As a general rule of thumb, speed beats armor while mass beats flesh. As long as we're comparing bullets of similar construction fired at rifle velocities that is. Large, heavy, relatively slow projectiles tend to penetrate through ballistic gelatin and other liquid - like substances better while M193 55 grain 5.56x45mm NATO fired out of a 20 inch barrel (roughly 3300 fps) is notorious for penetrating body armor that will stop most other bullets.
I figure that MJOLNIR shields at least sounded like they were almost a non Newtonian fluid based on descriptions given in The Fall of Reach. I could be wrong