If you're bugging out, you have to know WHY you are bugging out. Under what conditions do you leave a known environment for a HOPEFULLY better one? Something is forcing you there. USUALLY it's long term hunger or extreme danger in your current location. You are lucky enough to get to whereever your BOB is, and you know where you need to go.
You dont' mention vehicles, and I wont guess - so I'll assume you're hoofing it.
Every single thing you carry will chafe you, light or heavy, everything wears you down. Until about the third day, when your body will start adapting to the demands you're making. You've got an AK and a glock. Shooting schools give you a false sense of how much you have to shoot, it's because you're training, and it's not a realistic idea of how much you may have to shoot. There are not "El Presidente" survival shooting scenarios, now matter how many actions movies you've watched.
You mentioned your SO, so assume she'll need ammo/gun too. But again, you didn't mention that.
Perhaps it's better to go with potential scenarios.
1. You're on your way, and you hit a government roadblack. No amount of ammo is going to get you through - null. Think you're smarter? They TRAIN for this kind of stuff, they're going to have an observation post WAY before you can possibly see the roadblock - your existence is already known, no sneaking away. Think NOT? Think again, the army and marine corp TRAIN for "urban pacification" and they're not stupid, IP/OP's are standard procedure.
2. There's an impromptu roadblock, manned by 3 people with guns. Roadblocks are placed by people who are in their sphere of influence, your first shot is going to draw MORE shooters. again, you can't win.
3. You're walking and get ambushed - odds are whoever ambushed you was waiting until you were WAY into the killzone, you're already dead. But let's say you survive, you'd be CRAWLING somewhere - the bigger and heavier the backpack - the worse off you're going to be. You'll lose everything in it as you shed it to escape. Your "I dont need caches" mentality, has just insured that someone is going to be making babies with the girlfriend/wife you brought along, because your hubris has disarmed you in a hostile environment.
4. You are waylaid by someone with no sense - in THIS scenario, you MIGHT have a chance of winning. Let's hope you don't get wounded.
5. You get sniped - no winner here. You're a FAVORITE target, know why? Because you appear to be well-armed and carrying a LOT of supplies.
6. someone sees your gun, assumes you are a looter and bags you OR calls in the FEMA goons and THEY bag you. FEMA lives for this stuff, if they don't relocated you to a "safe area" they'll strip you and send you on your way. It's protocol.
In nearly all situations where you and only one other person are traveling alone, the best way to travel in by leaps and bounds. It's also very tiring and time consuming. But it's a must in an urban environment, or where any habitation is spread out. Never ever have both of you out of cover at the same time. 100 yard hops, or longer, depending on terrain. One covers the other and glasses the distance for threats while you cover the terrain. At times you can travel together, but I would advise against it. While you're crossing some open area, you come under some kind of fire. Your spotter sees the bad guys and you're 100yds out, with no cover, and the bad guys are 250 yards to your oblique. Either your support person works their way around to take them under fire, or they're equipped with a hunting rifle setup and can tag them at 300 yds. Either way, you've gotten into a fight, and your job was NOT to get into a fight, your job was to safely bug out to wherever. Congratulations, since you counted on walking to your bug out location in five days, you sacrificed water and food for ammo - and you've just added at least one more day to your trip.
It's a young man's folly, he thinks he can fight his way everywhere, and that having more guns and ammo than the next guy will help him win a fight, then some 12yrd old with a pump action guarding the cornfield 22 zaps him in the melon, because you can be darn sure the 12 year old is in a prepared position that his dad dug for him. he's heard you at least 200 yards away because he's not moving and you managed to knock into that trip wire he set up that knocked a tin can over.
The ONLY way to get 100 miles safely is to do it with a minimum of exposure. This probably means traveling at night, or with other groups. If alone, then it means you STAY OFF THE ROADS - roads are like mousetraps. In SHTF scenarios, two people traveling alone are asking for an ambush. So, let's say you contact someone and there is gunfire exchanged, by by SOME MIRACLE you are not hit. You should be disengaging and retreating to evaluate your path.
If you make 5 miles a day, on foot, you should count yourself lucky. You should not be trying to win any foot races, you should be worried sick you'll get in a fight. One single would to you or your SO and you're history, you're either the guy who couldn't get the girl to safety, or you're the guy who got the girl killed. Want to be a hero? Then win - and redefine your definiton of winning. In any firefight scenaries, Murphy's laws of combat rule. One of them is "if your enemy is in range, so are you." You just can't figure on winning against someone without taking damage. Shooting is a last resort NOT a first response. Think your AK will carry the day. Watch the movie, "southern comfort" - it should open your eyes.
I'd carry, six total mags for the AK and 3 for the pistol. Each AK mag weighs 2 pounds loaded. With the rifle, you've already got 20 pounds, add the pistol and gain another 5 pounds or so. 25 pounds of your pack is ammo/guns. Think you'll move fast with that and the other stuff you'll need? So call it 180 rounds of AK and 50 rounds of pistol If you get into any kind of firefight where that is NOT ENOUGH, then you're f***king up, and you need to turn back. If you WIN some kind of firefight, the bad guy will have ammo you can take. I just can't see a survival scenario where I will need even 300 rounds of ammunition. If I'm using that much, then I'm failing - because it means I'm not moving out of range. There is just no way carrying enough ammo for "winning my way through" 100 miles of SHTF terrain makes ANY sense when there are two of us and our goal is SAFETY. But let's say you do carry 300 rounds of rifle ammo. I'd say carry 3 mags, and the rest loose, same for the pistol - is you run those dry, then you're already hunkered up and you can reload the mags or your SO can from loose rounds. Divvy them up in vacuum packs enough to fill each mag. Load each rifle mag down to 28 rounds to avoid cycling problems the first 3 rounds. Carry softpoint ammo, the only reason to carry FMJ is to adhere to the NATO convention, forget THAT, softpoint is what you'd use to hunt game and makes much more sense if you have to shoot somebody to save your life that the round will do a maximum of damage.
there are just too many books out there where the survival scenario has involved shootouts where the guy with the most bullets, wins. It's makes for good adventure reading, but it makes for lousy survival.
What I'd do, if I thought I'd need ammo or guns along the way. Is map out three routes to my target area, and place supplies every 25 miles - socks, ammo, rations and water (those mylar ones). Since you know where the caches are, you can always get them when things calm down - but if you NEED them, you are going to need them badly. That's 9 caches. An additional pistol or cheap rifle in the cache immediately outside the urban area means that if you get stripped of your arms by FEMA, you can rearm. It also means that if you bug out from a place other than home, you quickly have some supplies to make your trek. If you get to this point, you will be quite angry at the universe for NOT caring at all whether you live or die, you will now survive based only on the thoughtful preparations you have made - all your whining if you get robbed or hurt will have no affect on the universe's indifference to you.
More important than ammo, are boots and socks, not to mention boots and socks. If you find a pair that you like, then get three, and break them ALL in, cache a pair at the halfway point. If you pick up supplies along the way, by the time you reach your destination, you'll have eliminated the stupid stuff you started out with, and you will arrive at your destination with more ammo than you started, which you will theoretically need ONLY at your bug out destination.
You can read, all day, about how a company of soldiers can march 30 miles in a day. Or a navy seal can swim upstream for five miles. The soldiers don't START OUT marching 30 miles a day, they work up to it - in your bug out scenario as well as mine, I'm not going to be training for several weeks, neither am I going to be, on average, 20 years old, neither will a mess tent be waiting for me, or a medic humvee if I can't walk. They train so that they trade their sweat for blood when it counts. TRY to 100 miles march on successive days, have someone drop you off at last nights stopping point. Don't pamper yourself at night in the comfort of your home, see how long it takes you to walk it with just 50 pounds in a backpack ON A ROAD that you wont be using when you really do bug out.
The ammo will become secondary after this.