9mm Non-dedicated Rig

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I believe they stated that because the standard carbine tube is 3/4” shorter than the A5/rifle tube, the spacer will eliminate the use of the bolt catch with said carbine system.

Appreciate your time explaining this, I’ve built a few 556 ARs, but this is new territory.

After sleeping on it, I will probably go with the A5 system I’ve got in the parts bin. Makes sense to me because I will be running shorter barrels/gas systems on the pistol lower; I feel like the A5 would tame any higher felt recoil from the shorter uppers.

Any given spacer will have the same effect on a carbine buffer and tube as it will with an A5 buffer and tube. Definitely nothing wrong with using an A5 for this. I’d have to measure again later, but you can probably simply use your A5 buffer in a standard carbine tube and spring. I’ll review the thread tonight to refresh myself on what you already have on hand to get you started. Half the point of a PCC is saving money shooting.