I have a full length review inbound but i wanted to go ahead and post my first impressions of the rail after the install. I have NOT shot the setup yet but i will be doing so on Saturday. Also, please note that this IS a preproduction rail and there are certain changes being made as i will note in this review. There may be other changes but i am unaware of them at the time of writing this.
The rail is very well made. The anodizing is a matte black and is type 3. The machining is clean and there are no sharp edges despite the rather intricate S shaped cutouts running the entire length of rail.
This thing is light. I dont have a postal scale so i cannot get exact weight but i believe that the quoted weight on the "other" site was 10.8 ounces including stock AR15 barrel nut.
Install is very easy despite my desire to ghetto gunsmith. I shaved my FSB, cut off my delta ring, pulled off the weld spring and the c-clamp as well.
The tensioning device for this rail acts as a thermal heat sink according to Samson and its really quite neat the way in which the whole thing locks up. No issues with fit, everything went on smoothly except for one minor hitch which i will detail later.
The diameter of the rail is perfect for my particular hand size and if i choose to do so i can wrap my entire hand around the rail with my thumb well over the top. Diameter of the rail at the widest point is 1.75 inches.
Perfectly round tubes are too hard for me to hold onto without a hand stop. This tube seems polygonal in design and this definitely lends itself to getting a better grip on the tube. I will have to shoot this thing in the Florida heat and see how well i can grip it with my sweat spewing hands and with gloves.
The lockup portion on the bottom of the rail that tensions it against the heat sink has two helicoil inserts. I intentionally tried to strip these out by over torquing the two bolts and was unable to do so.
When properly torque down (i dont have a torque spec for the two retaining allen head bolts, i will be calling Samson today to get one) the rail has almost ZERO flex. For a rail this small, light and thin im surprised by this. Normally if you apply pressure towards the end of the rail you can push enough to get the tube to shift location. Its not such a big deal as these rails are free floated around the barrel but if push comes to shove i prefer a rail that is 100% solid. The evolution rail is definitely solid.
The rail comes with three rail sections to add to the tube. I havent added these yet as ive never needed picatinny rail on my guns for anything other than a vert grip or handstop. I will be shooting the gun without a handstop for the time being as the profile of the rail lends itself to that style of grip very well. I will say that the way in which the rails mount up is quite nice. They will NOT shift on the tube as backer that secures the 1913 section is indexed to the rail itself. Once you torque down the rail sections they're on there to stay.
There are two anti rotation tabs that index on your upper receiver. This rail is not rotating, period.
I only have a few cons thus far.
The rail cannot shotgun open completely as the locking collar prevents the upper from hinging open completely as it butts up against the lower receiver. This is a pretty big deal for me as every time i open the receiver i cringe if i dont do it slowly. I really do believe that uppers/rails/lowers that prevent the gun from opening completely are adding undue stress to parts that dont need to be stressed in that manner. Im not sure if Samson is addressing this although i did suggest that he radius the FRONT edge of the locking clamp to remove the square edge there and he said it was already in process on production rails.
Im a natural born skeptic and while the rail locks up SUPER tight its only held on by two screws. The rail itself does not actually lock itself onto the upper or the barrel nut. It is held onto the thermal collar by nothing more than friction and clamping action provided by two allen bolts. Now, let me say that the thermal collar DOES index onto the splines on the stock AR15 barrel nut so the entire assembly should not be rotating or moving. This is pretty neat as the profile of the rail, the profile of the thermal block and the actual anti rotation tabs provide TWO points of anti rotation to the system. I dont know exactly how much pressure is being applied to that area but i wasnt able to pull the rail off forward despite trying pretty damned hard. I think with the helicoil inserts, some locktite or rocksett on the allen bolts and you should be good to go for life.
The 11 inch rail is indeed 11 inches but the VERY front of my gas block is exposed. Not a big deal but if i had the option i would prefer a 11.25 or 11.5 inch rail to cover the shaved FSB completely. This is mostly a non issue and is more of my personal opinion being interjected here.
This isnt so much a con as it is an observation. The anti rotation tabs were very tight on my upper and gouged the material slightly upon installation. Truth be told i would rather have this too tight as it is a cosmetic issue and nothing more. I just wanted to point this out in case you sleep with your rifle at night and it requires plastic surgery if it should happen to fall and scrape its knee. Personally, i dont give a darn as the rail is locked on there. This is the "hitch" I alluded to earlier by the way.
Here are some preliminary pictures. I will be adding to this thread with more details and pictures once i get a chance to beat the rail up a little this weekend.