So I just finished my first ar pistol build and found out I'm being transferred to Honolulu. I have about 8 guns and all kinds of ammo. Ar15 pistols are illegal in Hawaii so I'm planning on leaving that at my parents house with a lot of my ammo (.22,9mm,.40and my 300/556/223) planning on taking my at rifle and s&w shield to the island and leaving the other ones. Is it logical to keep the ammo I have. Maybe around 2500 rounds combined or sell it? For the guns I'm leaving behind I planing on lubing them up real good. Is there anything else I can do to the guns and ammo. Or the guns? I'll get back probably once a year to shoot them? As far as the ammo I have ammo cans but should I consider selling it it keeping it in the cans with some desipac's

I have stored ammo in the garage, the shed, the attic, etc. for up to 25 years.  Even the stuff in the hot summer/cold winter attic shot fine.

As for the firearms, again, stored in the attic, in the rifle/shotgun cases for up to 8 years (longest I went without getting them down and wiping them off again) with no sign of rust.  I just make sure I put a good coat of oil (3n1 oil was what I used back then) on the outside surfaces and in the barrel/chamber and then don't touch the metal with your bare skin when putting it in the case.

We, my family, never had issues with rust on our hunting guns following the "no touch" rule.  My father-in-law, on the other hand, would blame his rust issues on spider shit, my mother-in-law moving them to vacuum the carpet (kept some of them in the corner behind the TV till he got a gun cabinet at the end of the hallway) or "someone" visiting the house handling them.

Keep the ammo in ammo crates or storage boxes indoors and you'll be fine.  It will outlast you.  As for the guns keep i'd oil them up really good, even maybe try some spray lube and just do it every time you are able to come back to visit them as maintenance.  Your stuff will be fine if you keep up with it.  Maybe see if  friend or family member will let you keep them at their house.

I think the ammo will be fine. Best to keep it in a closed container and indoors where it's temperature controlled. If that's not possible it will still probably be okay for three years even in a garage. I had 20 ga skeet reloads in my attic (Texas) for better than 20 years and it functioned fine.

There are lots products around for preserving guns in storage, from simple CLP to wax products like Renaissonce. For guns I keep in my safe which are not shot very often (like my deer rifle) I put  Rig grease on the action parts and Breakfree "Collector" in the bore and outsides, and put them in a lose fitting gun sock. Collector is specifically designed for storage where you don't want to spend a lot of time cleaning it off if you want to shoot the gun as you would with Cosmoline. Just wipe it down and you're gtg.

Keep it somewhat temperature controlled and it will last a century.

Keep the ammo in airtight ammo cans and you will be fine. Toss in some desiccant if it makes you feel better but it is not needed.

I have a couple mil-surp guns I only shoot once and a great while. The rest of the time they just sit in my safe. I had a tiny spot of rust on one a few years ago from sitting. It had been cleaned, lubed with Hoppe's oil and the exterior wiped down with Remoil. The Remoil area is what got a spot of rust. It cleaned up luckily.

I went looking for something I could use that would last but didn't require a cleaning before shooting. I tried CO Collector about 2 years ago. I just pulled the gun that had the rust spot out of the safe to check it. It has been 18 months or so since I shot it. Still looks good. This stuff seems to work. This is the stuff.

The bags are great if you plan to store them. If you plan to use them periodically then the bags might be a pain in the neck. They do work.

Another option is a gun sock or the Bore Stores bags. I have one of these and I use it for transporting a gun to the range but they are silicone impregnated so they will prevent rust.

One last thing. Do not store them in a standard gun bag or case. The cloth and/or foam absorbs moisture and will cause the gun to corrode pretty quickly. I made this mistake once. Luckily it was not an expensive or rare piece.

History- I live on the Gulf Coast of Texas, not far from the Gulf. I have, along with my Dad before me, stored our Ammunition in Military cans, in the house for a more constant temperature. I shoot my oldest ammo first. Right now in my M1 carbines, I am shooting, with no failures, 1952 vintage from the Korean war. My best luck with corrosion protection has been with Corrosion X or ReelX (they are both the same product, called the developer/old owner and asked}. They have taken the red dye out to save money so the regular oil color [light brown] is still all the same. It stays on better and works better than anything I have used. If it is in my safe, no problems for years. If it's out [the firearm] used or handled, it gets wiped with a small piece of leather shammy I keep in a small jar. This has worked for me. The CorrosionX makes a decent lube but there are better and is also a decent cleaner but if real dirty I start with Kroil, especially the barrel.

I'm shooting some 1949 8mm Mauser ammo right now. About 68years old. Put it in ammo cans if you can and your fine. Get some good oil. Breakfree Collectors is great and wipe your stuff down. Its for storage . Brownells or midway has it .

Look into VCI bags and emitters. Best protection for storage and the guns can be stored in a completely dry state if you want for decades, regardless of humidity. I have several long guns and pistols stored for over 5+ years in bags, no problems and they're ready to roll.

I usually buy surplus .30-06 for my Garand. The earliest you can get are usually from the late 50s, maybe 60s/early 70s depending. They look great, shoot great, and never had a single misfire. Aside from having a lot of dust, they otherwise shoot fine.

Point is, ammo lasts a long time.

Store ammo in mil-spec cans at decent temperatures and the life can be many decades.
I would not use the moisture absorbent packs in air tight cans.
Also this may vary for the “green” ammo (lead free primers ?).
Depending on environment weapons may sit for years oiled down or could require special purpose storage bags.

BoeingShield or whatever.

Not sure why everyone is more concerned about temp than moisture. I'd think that would be the biggest thing.

I'd clean and degrease 100%, then spray them down with the linked product.

With ammo, I'd buy sealed cans if possible. You could nitro-pack them I suppose.

Because moisture is related to temperature and temperature variations can cause condensation of moisture. It's not two things that are separate issues, they are directly related. 

Lube the weapon up real good and put in a silicone sock will be fine.