Peep Sight Rotation.
It goes without saying that you need to thoroughly break in your bow before you go hunting. An important part of the break-in process is getting your peep positioned in the string so it comes back perfectly every time you come to full draw. All archers should know this, but bowhunters miss shots every year because of peep-alignment issues.
Here are some preventative measures to help you avoid this bitter mistake.
Ready, Set, Draw!
First and foremost, before you ever climb into a treestand or go on a stalk, you should draw your bow, with an arrow nocked, to ensure everything is in working order--especially your peep's rotation.
If the peep isn't perfectly aligned, you can temporarily fix it by letting down and twisting your D-loop so it rotates on the string in the appropriate direction. (This is one of the least appreciated but most beneficial aspects of using a D-loop.)
There are a couple of ways to correct this problem when you get home, too. A tried-and-true method is to press the bow and add or remove string twist. You can do this from either the top or bottom cam, but the peep will rotate a bit less with a twist from the bottom because the peep is closer to the top cam. You need to shoot a couple of shots each time you tinker with the peep to let things settle into their new positions. This is a time-intensive operation, as it requires a great deal of trial and error to get it just right.
A faster and more consistent way is to press the bow, then take a single fiber from one side of the string (where it splits to go around the peep) and move it around the peep to the other side. You then take a single fiber from the opposite side of the peep and take it around the peep in the same direction. This ensures that you have the same number of fibers on each side of the peep. (You can incrementally rotate the peep by using this method, but not once it is fully tied in.)
When you installed your peep sight, you presumably adjusted it to come back in perfect alignment. Unfortunately, as you continued to shoot the bow, the string settled in and rotated a little clockwise or counter-clockwise. (The direction the string begins to rotate is the direction it will continue to rotate if left to itself.)
One of the best ways to minimize this peep rotation is to use a high-quality, custom bowstring from the get-go. I use Winner's Choice strings, but there are plenty of other great brands out there. These companies use the best string material available--I prefer BCY; Brownell's is top-notch as well.
These custom string makers also pre-stretch their products under tremendous force to minimize stretch once the string is on the bow. Their strings are then able to be "shot in" with as few as 30 shots. Once that's complete, the strings usually don't rotate much at all.
Today's custom strings also make installing your peep in the exact center of the string easy because many of them are made of two different colors of fiber. By separating the colors, you essentially split the string perfectly in two, so it's not as likely to turn during the draw cycle.
Don't Baby Your Bow
Shooting isn't the only thing that causes the string to twist and the peep to rotate. In my experience, bows that are kept inside the house and only taken outside to shoot in the backyard don't tend to change very quickly. However, when you take a bow into the elements (e.g., when you take it on a hunting trip), all change will be accelerated, especially peep rotation. Hot and cold weather, as well as high humidity, can cause the string to twist. To be completely safe, I expose my bow to a little heat and a little cold, as well as some serious humidity, before I go hunting.
My point is this: If you're barely able to see through your peep while shooting at home because of peep rotation, you're going to get yourself into trouble when you take the bow afield. A day of humid weather or serious temperature change will cause the peep to rotate enough to block your vision completely. You must start out with the peep in perfect alignment!
Caption: A misaligned peep sight (top) can ruin an otherwise perfect bowhunt. Be sure to inspect your rig while at the range and make all necessary adjustments so your peep comes back perfectly (bottom) when you finally get your shot in the field.