where can i buy firearms companies old prototype shells?

Are you looking for the ammo, or mock-ups of the guns without internal parts? If it's the latter, I suspect that these may get scrapped when no longer necessary.

Have you ever been to a gun show? No? Then you should go to your nearest Barnes and Noble book store and buy a copy of "Shotgun News". Most news stands will carry this too - and - they are online. If you are serious - a short subscription would be money well spent. In SN you will see ad for all the guns shows in all the states.

Nearly every gun show I have attended since 1968 has had at least 1 if not more - people who buy, sell and trade old shells and boxes. You can always find their table - it is chock full of old guys with big guts, old skinny dudes - all talking about how their grandpappy used to have boxes of ammo that looked like the ones on the table. These collectors and sellers - are the kind of folks you need to cultivate a relationship with. Some will advertise in SN - most wont. Most are very willing to trade - but not so much sell. If they have something you want - you get a better deal providing them a unique shell and some $$ instead of straight cash. (my way of telling you to open your wallet if you stumble across anything cool in your search - it can be important trade material later) If you arrive with an 3x5 card that has your contact info and a list of what you want - they will get back to you. They will be happy to see that 3x5 card - it means they are not stuck writing your contact info down when they could be making a sale!

Next - look at the forums online. Expand out to any other firearm that may have used the cartridge. Post questions. You'd be shocked what some 'normal' and 'common' folks have stashed in an ammo can. I have steel case 45acp ammo from world war 2 and some of the old Winchester Silver Tip 45acp that the silver tip still looks like the day it was made and ready for some werewolf action! I forget where I got it from back in the early 1980's but I just hang onto it.

Good luck.

Interesting question. The kriss k10 uses standard .45 acp. You are looking to buy as a collector, and unfortunately yours is a VERY small market. You need a professional for this. Old prototype shells (if you mean actual prototypes from the factory testing) are going to be supremely rare and extraordinarily difficult to track down (even if the owner is willing to sell, how are you going to find the one guy who has that one round he bought from a collector years ago and forgot he even has it).

Your best bet, without professional help, is to go to gun shows. Be available. Ask around. I guarantee that someone at a gun show will be interested in what you're talking about. Give out your information, talk to the people. Eventually, someone somewhere will run into this round, and if they have your info, they should remember something so unusual and will remember that YOU were looking for it. Dealers at gun shows get around. A lot.

Austin, why don't you just buy an airsoft version of whatever gun you can't buy in real life, and put that up for display? Gun companies typically destroy the "mock-up" versions of the guns they intend to manufacture... or they display them at their offices. They don't sell them to delusional kids who cosplay.

ummmm...probably from those companies, right ?