Please Help: SF 1 Cell Heads Won't Work on Nitecore Extreme Body!?

[PseudoFed]

Just got my Extreme yesterday. Let me say that the extreme head works well on it's own body, my SF Backup body, or on the VG 1 cell body. However, when I try to put my KL1 or KL4 heads (older), or my SF backup head on the Extreme body, threading goes good, but then gets very stiff. I believe I'm making battery contact though I do not want to fully tighten the head. Does not appear to be crossthreaded, and I did not yet crank down on the O-ring.

Any ideas why my SF heads which run well on other 1 cell bods won't light up on the Extreme bod?

Thanks....Jeff.

 

[PseudoFed]

Can anybody with the Extreme and SF heads tell me if theirs fits on the Extreme body. I tried again, and all my SF heads will not thread very far onto Extreme before the threading locks. Before even reaching the O-ring. Anybody?

 

[glockboy]

My Extreme body and SF KL4 head work, if you tighten the head all the way, it tight at first but keep tighten it until turn on, after that it easy.