JPK: I agree that some peeps do block a substantial amount of view. One that doesn't is the old Swedish jaktdiopter. I have one on a Husqvarna Model 46 and it works well for me.

I wonder if the following two fellows were Cork Poppers?

Old John Buhmiller, the barrel-maker turned elephant hunter favored the wide V rear {he must have been sober most of the time} mated with {oops, here comes the bottle...} a thick wide BLADE up front which according to Bob Bell in Gun Digest, 54th Edition, he kept painted white. Mentioned elsewhere, I can vouch for this painting business myself, though due to conditions here, often black serves best. Buhmiller favored this combination even over a large peep.

And some may remember the late Harold Johnson, the originator of the .450 Alaskan. Possibly he grabbed the whole jug, as during his years in Alaska for bear hunting and on the custom guns he made, he favored the SOURDOUGH front mated with an adjustable peep rear with the threaded aperture insert removed. Cited in Handloader August 1999.

Two more guys I would have liked to have in the discussion here and I'd have been happy to provide the bottle.

And then there is Craig Boddington. He has stated in print he likes the V/Bead for an open sight on big critters but finds the peep faster and more precise. I wonder if he is a cork popper? Maybe just sometimes...

So, back to the actual topic for a moment.

If I remember correctly, you actually asked for target types used for zeroing. I assume that means paper. At least it does for me. Not sure for others:

Here are several I find useful.

The large target is the Norwegian hunting test target. ErikD will be familiar with this one. The smaller ones are of my own design, using the principles of the norsk target.

Use whatever to set your sights, a small dot on a large white background, a round bull, an anchor-type or whatever. I frequently use a small 1" square of masking tape placed on the center of the Facing Deer target pictured below.

Once sights are set, the use of the silhouettes establish exactly how you use them on asymmetrical targets {not many round bulls in the field}. I submit that if a fellow has to go through some complicated holding or gymnastication to use a set of sights he's better off with different type, but to each his own. I place the top edge of the front sight where I want the bullet to go and shoot.

The Facing Deer is a symmetrical target, and very easy to hold on. The Broadside Coyote is less so, and ditto the Broadside Cow Elk. We shoot all of them at various ranges from field positions after zeroing, no bench allowed, but the point is that the targets have lightly scratched kill zones that cannot be seen with the naked eye when shooting. The targets do not lie. the shots are either in or out. I have used them to teach limits of shooting ability and they seem to be a bit of a revelation for some.

I consider an 8 inch circle to be a conservative diameter of a deer kill zone, and six inches ditto for the coyote. If a fellow cannot on-command place 5 shots inside the 8 inch kill zone on the "Elk" {with no shots outside the invisible circle} at a given range, then he shouldn't be shooting at a deer at that range in the field. In practice, I will take any shot given on a coyote or dog {even a mere wound is A OK by me} but the Coyote target is a good one for practice anyway, particularly for pistol when approaching a trapped yote that might "erupt" and break away when seeing the trapper.

The targets are instructive. Granted, small varmints obviously demand a level of precision far beyond 8 inches at 100 meters but for deer we find these targets very helpful when used at all ranges. I have seen many otherwise confident shooters throw wide shots on the targets, followed by excuses. As I tell my kids, a target, paper or critter, doesn't lie. You can either hit it, or you can't. I confess, part of the reason I quit using beads was that I got unexplainable flyers on these types of targets at ranges beyond 50 meters.

Hopefully they may be of some use to you.

Here they are:

The Coyote with the scratch tool for scribing the circles: