Upcoming new ice screws

At over 5" tall and 2 1/4" wide this old Fixe screw has few competitors.

I've only placed once, and it took some effort;the slots below the handle are intended for you axe pick to help screw it in.

I put three different screws in the freezer at 30*F for about twenty minutes.

The top screw a Cassin Thunder(an older aluminum screw with a steel tip) measure .923 at the screw tip, after the freezer .880

The screw body measured.875, then after the freezer .875

The Petzl(clockwise) measured .709 at the screw tip, then .698 after the freezer

The screw body measured .708, then .695 after the freezer.

The BD measured .764 at the screw tip, .764 after the freezer.

The screw body measured .753, then.749 after the freezer.

The BD has the most steel at the tip, and also the most complaints, at least on this site regarding getting stuck.

Chromoly is thermally a very stable material, aluminum is not.

I think the main problem with aluminum screws getting stuck is the use of dissimilar metals in regard to thermal expansion and contraction. 

With the aluminum body shrinking causing the ice core to get stuck.

Unfortunately, this is not all of the answer as to why a screw places better after being removed, then placed again.

I thought I'd add some of my experience here. 

Old style 4 tooth Petzl--gets stuck often

New style 3 tooth Petzl--gets stuck often during first 1-2 cm in ice, but if removed and replaced then goes in fine. 

Blue Ice--Seems to place well but the plastic knob broke off the hanger lever the third time it was placed :(   It will probably be warrantied, but blue ice asked my friend to go through the original store where he bought it, which is fair enough, but time consuming.  

I've basically switched completely over to Petzl 3 tooth, but I might carry one long screw in steel, just to be sure I can make a-threads if need be.  Then again, the longest lengths are where you save the most weight so....