jcutonilli
Ultimate Member
- Mar 28, 2013
- 2,474
OK, I re-watched the video and I will eat my hat if the bolt carrier is anything but a standard auto bolt carrier.
The .22 converstion bolt does not travel back far enough to interact with the "sear/lever/trip" that the echo trigger uses to prevent the hammer follow.
I do not own a 9mm AR rifle but, I would think that if you do not need a special fire control group to make the 9mm upper work, the echo trigger would work fine. That is as long as you use an auto 9mm bolt carrier.
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I suspect you will need to eat your hat.
The bottom of the Fostech bolt is visible at the end of Tim's videos (MAC). It clearly shows a chamfer at the location where it would contact an auto sear. The Fostech part is different from a conventional auto sear in that it has a tail/extra material. (see your picture above) I suspect that this chamfer and tail prevent a standard auto bolt carrier group from fully seating and operating properly. It is unclear if there are other differences, but the presence of this chamfer makes the Fostech bolt proprietary.