Yep, it looks like only the MOE SL hanguard will not work with the triangular cap.

I decided I really liked the Magpul SL handguard.

So I

- removed the flash hider
- knocked the front sight base taper pins out
- removed front sight base and gas tube
- took the triangular front cap off
- installed a round cap
- reinstalled the front sight base / gas tube
- installed new crush washer and flash hider
- installed Magpul MOE SL handguards

Took about 15 minutes.



With the Magpul furniture and the cheapo UTG 'placeholder' Mk18-style rear sight, this is still a sub-$500 rifle.