Can shoot under 250 FPS without any problems, lightens up your gun, and adjustable.
Works like the stock bolt guide.
Well i went and got one of these cuz i play indoor alot, so it was something that would help me out, and it did, i chrono'd my gun to about 240 FPS with no drop off or bolt stick problems, quite imressed, but i didn't really notice any difference from the stock bolt, or any other bolt guide, lubing it can be a mess sometimes (more like an inconvenience) cuz you might accidentally adjust the bolt guide while it's in your gun rather than remove it, but thats no big problem, this shaves some of the wieght off the upper part of your gun, so if you're going for a lighter shocker than this can help, and you don't have to maintain this guide as much as the stock or other ones because it doesn't have a rear bumper o-ring, instead it uses a little plastic washer, only problems i've had with this is that i've lost that washer a couple times and it's a pain to try and get it replaced.
Overall i'm pretty impressed with the way that the bolt guide works (under 250 FPS), can help your shocker shoot consistantly, but it really does work just like the stock bolt guide, so unless you have any particular use for this, just stick with the stock.
It seems to me, that you don't know how to adjust it properly, if are scared of messing the adjusment if you take out the bolt. The outer part of the bolt guide needs to be set. After it is set, you can take out and in the bolt without messing the adjustment.
Call NDZ to help you...