Does anybody have experience in uplifting an old retail/ bank safe into a gun safe?
The DIEBOLD Cashgard is a TL30 rated safe that looks to be able to be had for $3-5k and big enough to put a Secure-it system inside.
Any reason not to? The one I found doesn't look to be fireproof. Does a normal TL-30 safe provide decent protection in the event of a house fire?
@MartinHewitt your insight in the past has been invaluable.

Great you have found it helpful.

I don't know much about fire safes. It is difficult to build up knowledge without burning down houses. So I can't say that much about this topic. The Cashguards I have see are burglary-only plate safes. Really, really solid, but nobody put a thought about fire protection into their design. I do expect the content is heavily damaged in case of a fire. Actually every fire rating in the US not from UL is not convincing me. Even when truthfully measured there is the common shortcut of measuring the temperature only while the fire is burning. It is then ok if the content is destroyed half an hour later while the safe is cooling down and still transferring heat to the inside. In Europe we have our LFS (Light fire rating) with this shortcut. This is very common here due to price advantages, esp. with the 30 minute rating. Our dry wall is "cat litter" (that's how it looks) and expanded clay balls (exactly like these used for hydroculture). Fire protection is not as important here. Mostly stone buildings and the fire brigade is not far away. With a wooden building far away from the fire brigade I am sure fire protection is much more of an issue. Risk assessment is very personal.

I don't know where you are in the US, but that's quite a bit for a used TL30. Is it from a private party or a reseller who has refurbished it? It may be worth it if it's refurbished.

For fire protection, you may just line the thing with a layer or two of sheetrock then complete your build out. Put a strip of intumescent tape around the door. I don't think you'd be too far from an actual firesafe at that point. I'm sure someone more familiar with fire safes will have more/better details.

ETA: seems like alot of fire safes use sheetrock (moisture) to protect against fire. It still allows a fair amount of heat inside the safe though. Heat and moisture don't do well with metal objects. So while you may not have flame inside the same, you nay have enough steam to rust all your guns.

@MartinHewitt
Thanks for your insight as always. Any opinions on upfitting it to a SecureIt style interior?
Per everything I found online it is labeled as having 1/2" sheet body with 1/2" steel frame, whatever that means. Unfortunately there's no good drawings available.

Correct, I believe it was @TheSafeGuy that said the idea is that the steam will act as a temp regulator to keep contents below the 350 degree mark
I've also read similar regarding rust if not removed within 24 hours or so of fire

I picked up a Diebold cashguard for $700 dollars and I absolutely love it. But a couple things, it would offer NO fire protection.... and mine was only rated TL15. I built wood gun racks inside it and it's great. Night and day compared to the "gun safes" sold at the big box stores, just no comparing it. I don't think trying to make it fire proof is even worth trying, it was never designed for that and I don't think it would work. It would be a night mare to make a new way to seal the door for fire. For 3k though, look at banks that are under construction (remodel, changing names). And see if they are getting rid of the "portable vault" often they are not rated, but they are often fire proof but think weights in the thousands of lbs.... They are often "free" but cost a few grand to move....

I found a photo of the Mosler TL-30 someone here converted to a gun safe. I just can't see how to upload here a photo.

The safes banks use are all TL rated to various levels. The "portable vaults" ie modular vaults ARE all rated, but not on a TL scale. There's a different rating they use.
You're not going to get those for free, and it won't cost just a few thousand to move. It'll be a fair amount more depending on the actual size.

If you are putting it on concrete then you can add drywall to the outside and brick it in for additional protection with a fire rated steel door on the front with insulation mounted to inside to help
The drywall will work, Ie release water to cool the safe from the outside under the brick