This is a common mistake to think of when it comes to amsec safes fire protection.
Although I'll be the first to admit that many safe companies do many things that don't make much sense, I'm going to give AMSEC a little more credit here than you are.
After all, AMSEC is one of the largest safe manufacturers in the US that produces tens of thousands of safes each and every year. They have full time engineers on staff that work with these issues day in and day out. I'm confident that this issue was thought through, and the conclusion reached that this design was superior to others.
No "concrete" is a solid material. Gypsum board isn't solid either. It being "solid" isn't the point. Take an empty sand bag and fold it in half. Now, fill it with sand (not solid) and bend it in half.
Or....take that empty sand bag, lay it across your chest and let somebody swing a baseball bat at it. Now, try the same thing with it full of sand, and tell me if it makes a difference.
I'm not cheerleading AMSEC for any other reason than they build one heck of a product. Sturdy builds a better product than a lot of the big names too. I still think the AMSEC is better though
I'm not basing this opinion on what I read on the internet. I'm basing this opinion on 15 years of experience dealing with safes. 90% of my business is commercial, so if it's been burned, burgled, moved, or malfunctioned, I've seen it in person.
DryLight or other cement compounds are not really like cement. It's a plaster-pars type of substance and although it adds a lot of weight, it's not sturdy. It's capable of breaking easily, so assuming cement would add to the thickness/security/strength of the safe would be incorrect.
So let's discuss the 99% of safes built between 1850 and 1930 that were built like this. There are a lot of these safes still in use today, and for obvious reasons.
The fill material itself is not hard like steel, and it doesn't add "a lot" of weight, because it doesn't have a lot of moisture inside of it. It is not a material that you would use for a driveway or a building, but that's not what it was engineered to do.
The weakness of any steel on a brute force attack is the steel flexing. The more rigid the steel is, the longer the safe is going to remain intact. There are essentially three ways of making steel rigid:
Use thick steel. This is obviously the best choice, but creates two big issues. Steel is expensive, and steel is heavy. So now you have a really expensive safe that is too heavy to go into a house.
Form the steel into a rigid shape. Think I beams, or car frames. If you shape a thinner piece of steel, it becomes much more rigid. This can work out for the door frame of a safe, but you can't really do this with the safe body or door.
Lastly, you can Sandwich the steel onto another rigid material. Think cardboard. On its own, the paper is very weak. Take two weak pieces of paper, and place them on either side of more weak paper with some glue, and all of a sudden it becomes very rigid.
So now the question becomes this: Is Sturdy's 7 gauge steel body more or less secure than AMSEC which uses a 10 gauge steel body, 2 inches of composite fill, and a 16 gauge inner liner.
I am not an engineer, but here's the simple math. The Sturdy has a body that offers a total steel barrier thickness of .1793". The AMSEC has a outer steel barrier thickness of .1345", and inner steel barrier thickness of .0598" for a total steel barrier thickness of .1943". So AMSEC is using more steel than the Sturdy, not counting the rigid fill material between the steel layers.
* Some Types Weigh The Safe Down
Some gun safes with certain cement like compounds for fire insulators have weights that are ridiculously high. With safes that use 12 gauge steel, the weight will have too much pressure bearing down. Therefore, they have been known to literally fall out of square several years later. It also raises freight prices.
Safes are supposed to be heavy.
Please tell me which gun safe manufacturers (there are only two that I'm aware of) sell gun safes with ridiculously high weights as a result of the fire fill.
If you could also tell me which 12 gauge safes using this construction method have had issues with their "squareness" I would also like to know.
The vast majority of fire rated safes and file cabinets have been built using the exact same method you describe for over 150 years.
* It's Cheap
It doesn't cost the manufacturers much money to use this as an insulator, so it will seem like your getting a good deal.
Drywall is much more expensive
It's not the material that adds cost, it's the process. Filling a safe with any type of fill material is much more labor intensive, and requires a variety of machinery.
*
It's Is Not Good Enough
Cement compounds work best on smaller safes about 2 ft high and in really, really thick layers, unfortunately they do not work best for larger safes. When it comes to DryLight, a 90 minute rating at 1275 degrees is not much better than sheetrock's UL ratings for an insulator, and we all know sheetrock does not work like an insulator, but turns the safe into a dutch oven.
Then please tell me why every major safe manufacturer that builds fire rated safes builds all these huge safes with UL ratings. If these 6' and 7' tall safes using these cement compounds don't work, then UL must be wrong.....Especially on the safes that will withstand 1800 degree temperatures for four hours.
Sheetrock is not UL rated as an insulator, and to my knowledge, no UL fire rated safe exists which uses gypsum board. UL rates drywall as a flame barrier for construction purposes. A cement filled safe will outperform a drywall lined safe in a fire everytime.
There are other products gun safe manufacturers have used as well, but the bottom line is this. Millions of cement filled safes are being used daily, and the only safes with the UL fire ratings are cement filled. If all of the other methods were better, wouldn't more real safe companies be using them?