Not my first build, but likely my best

[masan]

Greetings Gentlemen, long time lurker here, though I am a relatively new member and first time poster.

Wanted to share the build I recently finished...
http://i1335.photobucket.com/albums/w665/masan7/IMG_0186_zps0539343f.jpg (http://s1335.photobucket.com/user/masan7/media/IMG_0186_zps0539343f.jpg.html)

This rifle was built in order to see whether I could build a rifle on the AR platform that could compete with the benchrest rifles that friends and family members who are IBS competitiors are constantly clamoring on about. ( I have been behind some of those rifles and they are addictingly accurate)

Parts:

20" Kreiger Barrel 1-7.7 Rifle length Gas
BCM Blem Upper Receiver (still cannot find the blem)
WMD NiB BCG
BCM Gunfighter CH
Magpul PRS
Syrac Ordinance Adjustible Gas Block
Centurion Arms C4
Stripped S&W MP15 lower
Geissele SD-E
Nigthforce 3.5-15x56 NXS
Nightforce 20 MOA Ultralight Unimount

I had to take special care mounting the Syrac Ordinance Gas Block. I was afraid to dimple the barrel for the two set screws on the bottom of the gas block, fearing that the loss of metal and subsequent pressure from the set screws would displace enough metal in the bore to cause a choke point in the barrel, which could swage the bullets slightly and degrade accuracy. Ultimately I decided to use loctite as the primary method of securing the gas block, turning the set screws until they only touched the metal of the barrel enough to pull the top of the gas block down to the gas port. After nearly 100 rounds there are no signs of carbon build up around the gas block, nor has the gas block shifted from its original index point.
http://i1335.photobucket.com/albums/w665/masan7/IMG_0047_zps74e793c9.jpg (http://s1335.photobucket.com/user/masan7/media/IMG_0047_zps74e793c9.jpg.html)

http://i1335.photobucket.com/albums/w665/masan7/IMG_0092_zps006af7a5.jpg (http://s1335.photobucket.com/user/masan7/media/IMG_0092_zps006af7a5.jpg.html)

The finished Product weighs in at just over 12.6 lbs.
http://i1335.photobucket.com/albums/w665/masan7/IMG_0186_zps0539343f.jpg (http://s1335.photobucket.com/user/masan7/media/IMG_0186_zps0539343f.jpg.html)

Currently, I am having good results from H322 and 77gr SMKs with the gas block tuned.

I was very surprised at how well the rifle performed, both during the original ladder testing and subsequent fine tuning of both the gas system and final load. The rifle shot far better than I could have guessed at the outset of this project and I am extremely pleased with the final product:
http://i1335.photobucket.com/albums/w665/masan7/TgtGfx_zpse49f0383.jpg (http://s1335.photobucket.com/user/masan7/media/TgtGfx_zpse49f0383.jpg.html)

I haven't had nearly enough time behind this rifle to truly know what it can do (I hope to spend this entire weekend behind the gun) but I cannot wait to find out. While it doesn't really compare to a true Benchrest Rifle, this little beauty has surpassed my expectations.

[SpankMonkey]

Very nice build OP. But you need to pin the gas block or dimple the barrel. You will have problems down the road if you don't, it's just a matter of time.

[masan]

I agree with you completely, in fact the gas block was discussed bewtween myself and others, concerning the least intrusive way to mount it with the least impact on the barrel. One of the main reasons the gas block was left exposed was so that I could easily see if/when the loctite fails. As this is a rifle that will be used almost entirely off of a bench I am not concerned about the gas block being exposed and will likely re-attach it using loctite again if/when the old loctite fails.

[dlh2689]

That rifle turned out looking really nice. I'm kind of jealous.

[jmnielsen]

With the gas block exposed I would do nothing short of pinning it. Which I can't imagine pinning would degrade accuracy but I'm also not an expert. I just know I would pin that thing and call it good.

[TehLlama]

If it's just a bench rifle, the gas block will be fine - but the recommendations now are preventative hassle avoidance - no sense thinking the Syrac has gone off when the block has just started to twist and go wonky on you.