4
That end piece is just a pig nose adapter. Remove the two allen bolts and the outer portion will come off. Then there will be an inner threaded portion that will unscrew out of the inner threads. Then you are free to add any M4 type buffer tube or folding adapter you like.
I just sold a Hera arms and Sylvan arms folder cheap, but one of these will work. Alternatively, I've added a KNS 1913 adapter and MCX folding stock a few times. Just be sure to get the KNS with the flange to retain your rear spring and detent for the rear take-down pin.
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Lastly, I currently have on a 556xi a KNS 1913 adapter with flange and Zhukov stock with Haga Defense 1913 hinge adapter. If you're looking for something unique, but very comfortable / functional and still side-folding...
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I just sold a Hera arms and Sylvan arms folder cheap, but one of these will work. Alternatively, I've added a KNS 1913 adapter and MCX folding stock a few times. Just be sure to get the KNS with the flange to retain your rear spring and detent for the rear take-down pin.
Lastly, I currently have on a 556xi a KNS 1913 adapter with flange and Zhukov stock with Haga Defense 1913 hinge adapter. If you're looking for something unique, but very comfortable / functional and still side-folding...
