I decided to build an 18" rifle using a melonite barrel and nickel boron upper and BCG from WMD guns.  

The barrel began as  an 18" 416R stainless, standard profile, rifle length gas, 1/8 twist 3 polygonal rifling (3P) from Black Hole Weaponry:





Receiver, pre paint (gunkote):



WMD NiB-X BCG:



The barrel and gas tube were sent to Wynn at WMD Guns for salt bath nitriding (SBN) or melonite.  Turn around took about 4 weeks.  Everything came back a beautiful, uniform deep black finish.  It took a bit of scrubbing to clean the bore post-treatment; you remove a brownish gunk to reveal a shiny black bore.  The barrel originally had a bead-blasted finish so it came back matte.

I had a few extra tubes, so I sent them in as well.  





Here is the final product.  The rails are the 12" Rainier Evolution series.  I love the light weight and slim profile of the Rainier rails.



The lower is from Kaiser Defense (wish I bought more of them when I could find them for $89/ea...), trigger is the Geiselle SSA.  Magpul MOE+ grip.
Receiver plate sling loop is from arfcomer I Kick Hippes, the SLAP - I love the SLAP. http://www.ikickhippies.com/  

Buffer is Spikes ST-T2 with a Sprinco white "standard weight" spring.

Wow, that is a fantastic rifle. You put a lot of thought into it and it shows. Anything you wish you had done differently?

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Thanks...  You know I learn a little bit more with each one and my paint work is getting better.    

I was having trouble with my airbrush that day on this receiver...looks OK but could be better in a couple of spots, so I might redo that.  Other changes?  I need to find a better barrel wrench and I have one of the Spikes on order.

Next, I'm waiting to find a brakeout comp for the muzzle.

I have that same barrel in black finish -  it's an awsome shooter .  Nice Work!

Great build OP - WMD have done a lot of work for me - they're great guys.

I bet all of that NiB feels pretty shlick! I run their BCGs, but haven't messed with the uppers yet.

Again, nice build. Get 'er dirty!

Range report:

1st trip out I was a bit all over the paper.  Upon getting home and cleaning I found I didn't quite get everything out of the barrel after the melonite treatment.  You do need to scrub them a bit and I found there was a little residue I could see just in front of the chamber.  So more scrubbing wih a brass brush and patches.

After getting everything clean I went out again and everything was much tighter.  I was hitting between 1.1-1.2 MOA average to center on 10-shot groups (measured in OnTarget software) using Prvi M855 at 50 yds resting the front on sandbags.  So I was happy with the results.  



With a little better trigger control and eliminate the two outliers I'm at 0.835 MOA.  Not bad using M855.  

Just curious: You mention regrets for not getting more of the  Kaiser Defense lowers. Is that because of the cost, or are there other reasons that make you like it over others?

Oh, I also love the look of the weapon.

Thanks, Rob

A brass brush is not a bad thing on a coated barrel?

Shouldn't harm it at all...they're actually the phosphor-bronze bore brushes from Brownells that I'm using...  But it isn't a coating that's applied to the barrel, it's the converted steel of the barrel.  The process produces an iron nitride layer at the suface that's around 55-65 Rc hardness (compared to about 25-32 Rc of the original steel).  Hard chrome is around 60-66 Rc for comparison.

ETA:  On the Kaiser lowers...they have some of the best fit and silky black finish of about any lower I've tried - and they were sold at a bargain basement price.  I believe, from what I've found, that they used to do machining on lowers for guys like Spike's and Noveske.  The partners who owned Kasier Defense split into JD Machine Tech and Kaiser Military Technologies.

Update:

Did some velocity testing w/XM193 55gr Federal - the new stuff with the square crimp.  Chronograph was at about 10' from bench.

10-shot string (fps):  3341, 3312, 3282, 3284, 3302, 3301, 3317, 3294, 3309, 3303
Average:  3305 fps
Std Dev:  17

Those are approximate of what a 20" barrel should do with XM193.  Maybe some of the marketing claims are true about increased velocity from polygonal rifled barrels and or reduced friction from melonite.  I convinced a friend to jump on the Surplus Arms & Ammo deal for the same BHW barrel so hopefully we'll have a non-melonited barrel for comparison data.