I have seen them but never used them. A guy at the gun show yesterday had them in sets of 5 or 6 dont remember the price or calibers. I have one that is adjustable for different calibers but basically works the same it does a pretty good job.
Wasnt paying attention, its just like the one mentioned above.
The bore sighters are a nice savings in time. I have so many calibers I use the Bubba method.
Put the rifle in a shooting vise. Fire off 5 rounds with the iron sights at 100 yds. If they are on the paper then adjust the scope to the center of the group.
Move out to 100 with the scope, you should be on the paper. Adjust as necessary.
Move out to 400, if your rifle is good for that range. You should be on paper, adjust and refire. Done deal.
Get one of those keychain lasers and take the keyring off. Use some electrical tape sticky side out on the part that will contact the chamber and hold the 'on' button down. Of course this only works with bolt actions or rifles that give clear access to the chamber. Go ahead and laugh, I've done it. In the back of your mind you may be thinking *******....that's okay too, I'm not ashamed.
I have one like Gunzzi mentions and it's saved much time and many rounds sighting in rifles and handguns. I used the "Bubba" method for the last 30-sumpin' yrs and did fine, but heck, I only paid about $40 for the thing (got mine from Midway) and it's quick and easy.