Randomly came across these guys.  They have a comp, flash comp, and muzzle brake.  Anyone used these?  Thoughts?  They look promising....maybe a tad expensive.

http://griffinarmament.com/accessories/centerfire-muzzle/

I have a M4SD II and like it quite a bit.  I use it on my RECCE and it helps reduce bounce when prone.  Allows me  to stay on target.

There are several dealers that offer better pricing, and with some you can get free shipping, or combine it with an order you are already making.  

AR15.com dealers: Aim Surplus, SKD, ADCO firearms, and Weapon Outfitters offer them.

Muzzle Device Video

Griffin is good stuff for the price.  I don't know that I'd go with the brake/hider combo, but I think them and rainier are the best bang for the buck in beakes––behind PWS, then Surefire.  If you just want a flash suppressor, there are cheaper and better options––like a vortex.

Looks like a good compromise between flash suppressor/compensator.

I just got my M4 SD II a couple days ago. I mounted it yesterday and I am leaving for the range in about an hour. I have the Battlecomp 1.5 and wasn't to thrilled with it. The Griffin isn't as well known, but everything I read about it was positive. They were a pleasure to deal with, answered all my questions and shipped right away. If you want to talk to anyone at the shop I will provide the email address to the man that I spoke to. I will post back this evening as to my findings.

Sorry it took me so long to get back to this thread. Well I took my Spikes M4gery out for a run with the M4 SD II comp installed. Let me say that I tried the Battlecomp 1.5 and wasn't really impressed. I fired 300 rounds the other day at the range and the M4 SD II did just as I expected and wanted. Muzzle rise was not even present. I was able to fire multiple shots as fast as I could pull the trigger and I was amazed how easy it was to keep the muzzle in the same position for each shot. This meant the grouping was extremely tight. I left my cell phone at the house but I will be going back next week and will be sure to get some photos. I know the Battlecomp has a lot more users and is by far the most popular comp out there. There was a definite reduction in muzzle rise with the Battlecomp 1.5, just not as much as I was hoping for. The 1.5 was also quite a bit louder than the M4 SD II. All comps are going to be louder than a A2 Flash Hider, but the M4 SD II was the most quite and the lest amount of muzzle rise. Between the two I prefer the M4 SD II over the Battlecomp 1.5. As I said before, it isn't as widely used as the 1.5 but everything that I found praised the M4 SD II just as I am. Now I want to try the Spikes Dynacomp and I will report back as to how well it does compared to these two. I may soon have a 1.5 up for sale, but the M4 SD II is staying on that rifle!!! I hope this helps some of you.

In my experience the griffin is a slightly better comp than the spike's Dynacomp.  The Spike's is a little quieter but puts out more of a flame when shooting rapidly.  Now if you are talking about the Dynacomp Extreme (the longer version) that's a horse of a different color.  The Extreme does a slightly better job than the Giffin.  Only issue is the added length.  Works great on a 14.5" pinned.  I did try one out on a 16" and it was nice but just wasn't a fan of the added length.