My short review of the First version of this bolt is here:
Imagine Derlin ACS Test
This is the Derlin ACS Bolt, Imagine model. Kingman has relased a second version of these bolts.
If your bolt has "steps" on the sides of it, you can send it to Kingman Tech Services and they will send you a new Verson 2 bolt. My turnaround was less than a week, Monday to Saturday.
Anyway, on to the notes.
Here is the first version of the bolt. Note the sides of the bolt. The 'steps' indicate it is the first version.
This, on the other hand is the new version. Notice it has no stepping- The bolt is smooth all the way down its length. This isn't where the changes stop, however.
The air inlet is also different. Perhaps a longer oval-shaped passage will result in less blow-back, which plagued the first bolt badly.
Also, although not visible in the pictures, there are some minor surface cuts and changes.
- The front half of the bolt is slightly larger, probably to seal better. It is so slight a change from the rear half that it is hard to see on the bolt, but it can be felt.
- The bolt has a detent cutout on each side, as opposed to just the single side of the older bolt.
- About 1" from the nose of the bolt, there are two lines cut. It almost looks like they tried to make an O-ring effect out of the derlin itself. There's a line, then nothing, than another line. I can only guess as to the purpose of this, and I think it may be an attempt to seal against the barrel during firing.
Also, on the first Imagine bolt, when it anti-chopped and if it faield to recock, the recocking handle often burried itself inside the bolt, leading to some shaking and poking before you were able to pull on it and recock your gun. On the new bolt, the handle does not fully enter the bolt, so this shouldn't be much of a problem. The ACS spring "feels" lighter as well. I can't test this though, so your results may vary. If so, the recocking problem may just disappear altogether.
The new handle stop position-
Conclusion:
If you have the first version of the ACS Bolt, and are unhappy for any reason, I think this is worth the small cost of sending it to Kingman.