I posted this on another thread...
The DD Mk18 Mod1 is the civvie street version of the CQBR/Mk18 of JSOC issue. It is also used in several variations by numerous NATO SF teams working with JSOC.
I have a DD Mk18 Mod1 that I have about 1000rds through right now. So far I have had no issues with the rifle.
The rifle is wel balanced and compact. OEM has the rifle come in with a MOE stock, but I replaced this with a SOPMOD stock ASAP to give me the sighting ergoes I am familiar with. I also added a VTac VFG and an ADM Mod11 sight mount for the Aimpoint T1. I use a Pig sling with QD that pops right into the mount immediately below the buffer tube.
This setup might weigh 7-7.5lbs.
When working the long shot with the issued rifle I was able to tag a static target at 500m using a T1. In the intended ranges for this type of rifle accuracy is usually superior to the operator. I figure that I'm getting about 1.5-2.0 MOA from the DD Mk18 Mod1. In timed headshots at 50m I'm usually scoring about 60% in a two second window from low ready. At 20m, same timings I'm making 95% or so. At 10m with a one second window I'm scoring 99-100% from low ready. All shots are controlled pairs. So clearly the rifle is comfortable, fast to bear, combat accurate and has a better than acceptable recoil impulse.
I recommend keeping the rifle wet, I'll use whatever CLP I can get, but some use lithium grease, froglube etc. The only time it choked was sixty rounds into a session where I neglected to do a weapons check prior to lighting it up.
I'm planning to throw a irlam on it sometime to support a nv monocular in the future. The irlam will add about 0.75lbs.
On such a compact platform you have to plan very carefully where and what accessories you put on it to avoid screwing up the weight and balance of the rifle.
Hope this helps...
-S.