Picked up a brand new Kel-Tec RDB about a week ago.  Finally got it to the range today.

The first 70 or so rounds, the gun worked great.  No problems at all.  Then the bolt locked back in the open position and I can't get it to close at all.  Bolt release does nothing and doesn't seem to even have any tension on it almost like when the bolt is closed.  Charging handle is just slack and doesn't seem to have any engagement with the bolt carrier weldment.

I was able to field-strip the rifle and pull the bolt out.  But when I re-assemble it, it's back in that "locked to the rear" position.  I also noticed when disassembling and reassembling that the action spring is free of the bolt carrier weldment but in the parts diagrams and disassembly instructions it appears to be "captive" inside of the weldment.

Ammo was standard 62gr green-tip.  Rounds were fed from a 20rd Magpul and a 20rd USGI mag.  The final 30rds were shot with an AAC 762-SDN-6 on the rifle (attached via 51T Blackout flash hider).  There was no felt change in recoil with the suppressor and no gas to the face.  Since it worked fine until that point I did not alter any gas settings.

Any ideas on what happened and how to fix this?

Can you post some pics? I had an issue when i reassembled mine once I managed to assemble it in such a way that the bolt & carrier was "stuck" back. I've never been able to replicate the issue since but it sounds like you might have something similar going on.

Think I just found the problem.  A google search turned up this thread here:  https://www.ar15.com/forums/t_6_43/469684_Kel-Tec-RDB-Malfunction---known-issue.html

The action spring on mine did the exact same thing.  It IS supposed to be internal to the weldment and mine let go already.  What a stupid, shitty thing for a gun company to fuck up.  I'll have to give Kel-Tec a call and return it so they can fix it.

Glad you solved it. Let us know how they take care of it for you.

OP, what is the range of the serial # of your RDB?  After reading that thread, I took mine down to verify that it had the proper depression/welding spot.  Luckly, mine is in the early 700 range.  So far so good.

Not sure of the "range".  My serial number is Z0LXX where the "XX" is a number between 00 and 20.  Mine looks like it has the proper depression and weld.  But apparently the weld let go anyway.  Not very reassuring even if it gets fixed.  

Fuck, I was really stoked that these would be reliable and break the Kel-tec curse

One sample in the ones they've got out there is hardly enough to cause mass panic. Mine's been 100% as have loads of others. Having said that we should look to see if this becomes an ongoing issue or if this is a one off. Also to see how kel tecs CS handles it.

Kel-tecs curse is that they will never be anything more than range toys.  They have cool innovative ideas but I really think that some people expect way more out of them than what they really are, I really don't see why this problem is a turn off for people interested in the RDB. I'm sure they'll fix it.

Overgassed the ever loving daylights out of it!!!

Doesn't TFM say to adjust the gas with a can on?

Not too surprising you broke something like that...

Actually, no.  "TFM" doesn't say anything about adjusting the gas with a can on it.  It DOES say that "too much gas pressure on the piston will give a sharper recoil" (which it didn't with the can on it) "and deform the ejected cases" which again, it didn't.

Interesting - my  RFB manual definitely does, I just ass*u*me*d the RDB would too.  I'm sure Kel-Tec will take care of it regardless, but that's still my suspicion on your "what happened?" question.  I could be wrong - you might just have gotten unlucky, or it could be all the "horrible Kel-Tec QC" that I hear about on the interwebs.

Ive got 2000+ rounds through mine, no issues. Biggest issue with these rifles is the adjustable gas system. That is a defective op rod though, it has happened to several others.

Contacted Kel-Tec back around 02/20 I think it was, via the contact info on their page.  Received a reply the next day saying to send in just the bolt carrier group so they could fix it.  Said it would take "5 to 8 weeks" to fix.  Shipped it off that day and they received it the next day.

Received the bolt carrier group back yesterday and the BCG is fixed and the rifle appears to work fine now.  Turn around time was less than two weeks so that was great.  I did write "RDB Bolt Repair" all over the box as someone in another thread suggested that doing so expedited the repair.

Haven't had a chance to shoot the rifle again yet.  But I'll definitely give props to Kel-Tec's customer service.

Glad to hear it, thanks for the update - and here's hoping your rifle runs right from now on!

Glad they took care of your promptly thanks for sharing OP