Re: Magpul B.A.D. lever
Doorkicker and sobrbiker make some great points. If you'll never use one downrange, there's no need to get into the habit of it back here. The most significant advantage of the BAD lever is on malfunctions where you're moving your hand off the pistol grip to manipulate the bolt catch. For me, malfunction drills are easier for me in multi-gun comps, so the BAD lever works for me. YMMV.
I'd have to disagree with sobrbiker a bit on one point though. It is possible to manipulate the BAD lever without your finger poking into the trigger guard if you're careful. While many weekend warriors may not exercise the care to do that, others can and often do. If you're used to resting your finger on the lower receiver, then bringing the index finger directly down will release the bolt, while reversing that movement and racking the charging handle will lock the bolt to the rear. When acclimating yourself to using the BAD lever, you have to train yourself to manipulate it safely. Obviously, the point of fine motor skills deteriorating under stress can absolutely hurt you here, though manipulating the bolt catch during a malfunction is a fine motor skill anyway.
Bottom line: try it out, it's only a $30 experiment. Train yourself properly and safely. But if you roll with an M4 variant in real life scenarios, keep practicing your original malfunction drills since your issue won't have the BAD lever. That's my take on the issue.