After many years of trials and tribulations using JAC, Spikes, and CMMG .22 conversions on registered lowers and semi autos I have several uneducated opinions about their design and reliability.

1. Why does the bolt not have a hard stop? It seems timing the bolt cycle would be easier if it simply had a hard stop under recoil so that all ammo regardless of power/velocity would be forced to cycle a limited amount of motion in the bolt. Leaving it open ended just makes timing ammo (cutting springs) more difficult. With a set amount of bolt travel different power springs could be offered in a set length for different types of ammo. I am not an engineer but this and the extractor issue are the 2 biggest annoyances I think are present in the system.

2. The extractor design has in the past been weak. A tunable extractor like those found in a 1911 would save a lot of issues once you lose tension. The way the part is designed now there is no way to adjust tension w/out heat/bending. I like using my 1911 tension tool to set my extractor tension correctly every time and it seems something similar could be used on these bolts. After all its just a claw that needs to grip the case rim long enough to contact the ejector. Several of mine were machined in a manner which grabs the case rim well enough to pull the round out of the barrel but don't hold it against the bolt face long enough to contact the ejector casing stovepipes. In lieu of this simply manufacturing/finishing the part to work correctly so we don't have to tune them would be great.

3. Bolt bounce has been an issue but the ball detent improvements help greatly.

I believe 90% of the troubles people have seem to reside with the extractor losing tension causing jams and the inability to work with a set amount of bolt travel causing some types of ammo to be stripped too quickly off the magazine (long stroke/high velocity ammo) or perhaps too much energy being expended moving the bolt back too far by weaker ammo. These bolt stop devices meant to hold the kits steady in the upper seem to address this as energy is used up when the assembly moves. I really would like to see what a hard stop just beyond the travel needed to eject a round does to the reliability of these kits.

I traded a glock kit for a cmmg kit in SS years ago.....and its run 100% in my 16" middy, my 20" a1, 11.5" 733 and mostly in my 10.5" sbr. I use mostly cci subsonics and suppressed on the current 10.5".