Does anyone know if the PH 1100 and 1200 Santa Barbara receivers retained the standard M98 action screw thread (1/4-22) or did they change to 1/4-28?

On Numrich and they have action screw sling swivels with both thread sizes.

Also, I'm planning on making target rails. Any idea what size the holes/threads were? I've ordered hand stops, so I may have to wait and measure the thread.

Thanks.