I suspect that the problem is with the quality of the bits and the
hammer drill.

SDS grade bits from Bosch, Milwaukee, DeWalt, etc in an SDS type
hammer drill should solve your problem.

Powder actuated guns can certainly shoot nails through 2x4 into
concrete or steel. The hammer drill method is better. The PAT
tool may not fully drive the nails to full depth and/or may blow
out large chunks of concrete.
______________________________
Keep the whole world singing . . . .
DanG (remove the sevens)




wrote in message
ups.com...
Went through 4 masonry bits installing framing for windows in a
concrete foundation. Some holes were very straightforward - the
bit
cut easily to the full depth. Others either immediately
destroyed the
bit (remove the carbide flange) or would just not cut into the
stone,
like it was hitting some aggregate that was very very hard.


Suggestions anyone? Can I use a power nailer to attach 2 x 4s
to
concrete?