Tandemkross Cthulu 22/45 Lower and Volquartsen Competition Bolt Compatible?

[Flatland Shooter]

I purchased a Tandemkross Cthulu 22/45 Lower to put under a Volquartsen Mamba X upper.  With the factory Voltquartsen/Ruger lower the Voltquartsen gun runs 100% with CCI Mini-Mag and Standard Velocity ammo.  But with the Tandemkross lower, it will not allow the Tandemkross hammer to drop. Per the Tandemkross instructions, the pretravel and the overtravel screws are correctly set.

 

Put the Tandemkross lower on two different Ruger Mk 4 uppers and on the Volquartsen Mamba X upper and all looks good.  Installing several different Ruger Mk 4 bolts (two are stock and one has Volquartsen internals) all guns run great.  Add the Volquartsen Competition bolt to the mix and the hammer will not fall.

 

Visual inspection shows no difference between any of the bolts, but the Volquartsen bolt will not work with the Tandemkross lower.  No strange wear marks are seen on the bolt. 

 

I'm at a bit of a loss.   Any suggestions?

[Farmer]

Does the trigger pull like it’s disconnected? Maybe there’s a different cut that affects the disconnector. 

[Flatland Shooter]

Farmer, I hope you are on the right track.

 

After no responses on the Enos forum I touched base last Sunday with "22 Guru"on YouTube about my problems. He shared emails that he received from Tandemkross and Volquartsen.  He keeps tracks of his videos and answered my questions within minutes. It turns out he has several Volquartsen Mark IV bolts and only a few have the same problems as me.

 

Tandemkross indicated a problem with their disconnector and recommended 22 Guru contact Volquartsen.  Volquartsen indicated problems with some of their Mamba bolts that may not work with all disconnectors.  They recommended a switch to their high end disconnector and advised that the change "may" solve the problems.

 

Further research on the web indicated that just changing the disconnector alone may cause additional problems.  So  I have the Volquartsen Accurizing kit on order.  This kit includes Volquartsen's target hammer, sear, and disconnector in one package.

 

Hopefully this will fix things.

 

Thanks.

[Ltdgun40]

Any news on a fix?

 

[Flatland Shooter]

Got the Tandemkross lower back from Volquartsen late last week.  Put it on the Mamba X upper and it seems to be working ok.  I will test fire it and report back the results.