I’m not sure what you mean by “visible”.
To cowitness iron sights with a red dot sight (RDS), one turns off the RDS. One gets a proper sight alignment front/rear of the iron sights THROUGH THE WINDOW, with both the rear and front sights visible, ideally in the lower 1/4-1/3 of the window. The iron sights must be just the right height to protrude into the window AND align for an accurate shot.
Then one adjusts the iron sights for Point of Aim (PoA) to Point of Impact (PoI), just as with any gun with iron sights but while seeing the sights (visible) through the window.
Next, one turns on the RDS. One looks through the window and adjusts the position of the dot in the window until it covers the same PoI produced by the properly aligned iron sights that are visible through the RDS window. So, using either sighting system, alone or together, one will get the same bullet strike. This is cowitnessed.
The front and rear iron sights must both be visible through the window for this to work. If they are too low to protrude up into the window, as is the case with the extra tall Leupold Delta Point Pro (DPP) RDS which blocks use of the OEM iron sights, they are useless for any kind of sight alignment as long as the RDS is mounted to the gun. The rear sight is always “visible”, but unusable, and the front sight is invisible when the gun is held in a firing orientation.
The shorter and more common height bases of other RDS’s allow the OEM S&W suppressor height iron sights to be seen through the RDS windows of almost all other RDS. This thread is about the OP’s disappointment that his chosen sight (DPP) would not work with his S&W OEM suppressor height (higher than normal) sights. He solved his problem by getting a standard height Trij RMR which allowed both front and rear OEM suppressor height sights to be visible in the lower 1/3 of the RMR window and therefore used for cowitnessing.
I hope this clarifies the relationship between visible and cowitnessed.
CO-WITNESSING PISTOL SIGHTS AND RED DOTS? | Gabe Suarez Blog
