From left to right:

1. ANS designed the "quick" pull bolt (in blue) which is basically designe like the old push button pull pins. When the button on the back of the bolt is pushed teh 2 bearings will retract into the the bolt. No pull pin necessary. Later system X made some half aluminum/half delrin bolts that used this same system. These came in pre2k and 2k+ only.

2. Second in pics (slik )is known as an Evo (evolution) style pull pin system. A spring loaded detent is used to hold the pull pin in place, which has a groove around the middle of the pin to allow the detent to rest. Notice the detent is located away from the back of the bolt within the hole
*(available in all bolt designs)
*(see pull pins in tech section for an expample of a bolt detent removed from the bolt)

3. Thrid (shocktech) is the same as second other than the detent is located on the opposite side of the pull pin hole (toward the back of the bolt)

4. Fourth (Old Evolution) is the original standard style. A push button (or non evo) style pull pin must be used. ther is not a detent within the bolt to prevent the pull pin from falling out.

5. Fifth is the twist lock bolt, this bolt was created by DYE and does not require a pull pin. The bolt has 2 steel pins (dog ears) sticking out of each side of the bolt where the pull pin hole would normally be located. The back block has 2 "L" shaped grooves for each pin, inside that groove is a detent to prevent the bolt from twisting out. (much like the older mag barrels). On this type of system no other bolt or back block can be used without modifications. (I'll take pic later)

6. Sixth is a cam locking "pull pin" that actually twists to release the bolt. Like the Fifth they are only compatible with each other. (pic later)

7. Seventh is the off-set pull pin, rather than the pull pin going through the center of the bolt, the pin is located lower on the back block and goes through a slot on the bottom side of the bolt. I assume this prevents from accidently putting the bolt in upside down. (no pic at the moment)

If you have anything to add please feel free to contact me on www.customcockers.com/forum as K.macocker
thank you,
Kmac