Guess I can post this here now since I replaced the KAC RAS with the Centurion C4! 80% pistol build, 10.5" barrel. LAW folder with KAK blade. DD rear sight. OTAL-C
, Magpul, Tac-Con 3MR trigger. Recently added a WMLx.

Here it is tucked away in my Haley Strategic INCOG sub-gun bag. This is my truck gun.

Very slick there, my friend, and a cool concept. I hereby dub thee "The Backpack Bandito", aka "The Mini-Me Maurauder", aka "Secret Sauce".

Watch your fingies near muzzle. You may want to also try out one of those offset HSP mounts with the WML. Much more comfortable. I'll check to see if I have any extras laying around.

Great looking rifle!! Who makes that fsb?

Thank you sir! Love the names.

Muzzle device is a compensator, so closed on the bottom. It does a very good job of deflecting the blast up. That's also why the Magpul AFG. Haven't seen the offset mount, I'll check it out.

Thanks, one of my favs and really fun to shoot. Just simple irons but they keep you honest (and sharp).

The FSB is from DEZ Tactical. Very nice piece. This was a virgin barrel and I didn't want to drill taper pins for a std FSB. I found this and the screws lock it down solid. There is one in the bottom as well and that matched up with the factory dimple on the barrel perfectly. Its a dead on F marked post.

https://shop.deztacticalarms.com/A2-Fixed-Front-Sight-Clamp-on-750-w-Bayonet-Lug-DEZ-1035-GB.htm

Cutout Larue 12" SAT rail.

Kickass.

Nice mod! Good looking rifle.

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Love it.

Keep 'em coming, gents.

I have a 80% FSB build in the works. Sort of a CAR-15, Colt XM177/GAU-5/A inspired but built on a flat top upper. 11" ish barrel, TBD when I start chopping the 14.5. In the meantime I am also working on a Block II FSP.  14.5" SOCOM barrel inbound.

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Waiting to see which lower I will put it on.

I like that a lot.

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A few updates to Post #1 on Page 1.

Enjoy.

At the request of "mhbaker81" I'll post my latest "Free Float FSB" build. I decided to do the "kino" thing with this guy.

Build details:

"Mega Arms" forged receiver set
Faxon SOCOM profile 12.5" barrel
"F marked" FSB with a Magpul pro rear sight
Midwest Industries 11.5" Combat rail
Toolcraft BCG
Radian Raptor charging handle
Magpul K2 grip
Geissele maritime bolt catch
Battle Arms pin set
Battle Arms magazine release
Battle Arms short throw ambi safety, "short crank" and "scallop" levers
Mega trigger
KNS anti rotation pin set
Vltor A5 buffer system
SBA4 brace
Arisaka finger indexer
Streamlight Protac HL-X on Arisaka offset scout mount with Cloud Defensive tape switch mount

The "kino" build was a lot of fun and a little complex to get perfect. I have access to a cnc 2-axis Bridgeport and made a couple custom fixtures to make this thing correctly. How I did it:

First I had to locate the FSB at the mid length gas position. I made glorified barrel dimpling jig that pilots on the gas port or the barrel at the carbine gas length position and allowed me to put a dimple at the midlength position. I then made a fixture to drill and tap the FSB to temporarily locate and secure the FSB to the barrel. The jig has a tapered set screw in the shaft that you tighten though the hole in the bottom of the FSB and pilots on the gas port hole in the FSB making it perpendicular to the mill. Then I could precisely drill and tap the bottom of the FSB for a #10*32 set screw. After that I milled off the bayonet lug and sling lug from the FSB. Put a little cold blue on the fresh exposed steel to give it a finished look. The Faxon SOCOM barrel isn't the same as the BCM 12.5" barrel profile which created it's own challenge. The BCM barrel is the same .750" diameter from the gas block journal basically all the way to the muzzle. The Faxon barrel has a .750" gas block journal but then steps down to .730" heading towards the muzzle. So a standard FSB wouldn't fit without something to take up the .020" difference. I used a lathe to turn a .750" OD steel tube to .730" ID (only .010" wall thickness!) and made two cylindrical shims to fit in the FSB to make it tight to the barrel at it's mounting location. Next I made a fixture to rigidly hold the barrel so I could accurately locate the tapper pin holes on the FSB barrel assembly. I then drilled and used a taper pin reamer to install the FSB. I then installed the barrel without the FSB into the upper receiver and attached the handguard. The MI combat handguard is particularly nice for this this project not only because it's high quality and competitively priced, but also because the MLOK slots are not offset from each other like other rails and the first slot from the muzzle end is a full slot, which makes the spacing pretty perfect. With the upper assembly in the vice, I located off the barrel edge and muzzle to mill the access holes in the each side of the handguard for the taper pins. I used a band saw to rough cut off the section of rail that had to go. Then I was able to use a 1/4" end mill to remove the remaining interfering material. Put a little aluminum black on the raw aluminum to finish the handguard out then installed the FSB and flash hider. I personally think it turned out pretty slick and has a professional/stock look to it.  

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Guy's a pro... Nice mod, my friend.

Looks factory, to me.

Very nice, my Ricky! This is the 0321 "Fat-Finger" build... Trigger fingers so jacked, they require custom lowers / trigger guards to accomodate the girth! Well done.

I'm really loving these new M-lok C4 rails. Also genius how they're designed in a way that the CMR covers line up with the cuts on these. I've been debating updating my Midlength on page 1 with one of the FSB cut versions, but I'll likely keep that one as is.

I guess I know now what type of rail will go on my next build... God be damned... It never ends!

So this is possible...

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Very possible...

This is my only free floated FSB build...

Mega Arms GTR Ambi lower and upper with a Noveske 10.5" barrel, pinned FSB, Vortex FH, Centurion Free Floated Rail... "WMD" LPK w/Nickel Boron Trigger/Hammer & JP Enterprise springs, JP "Enhanced" buffer spring, Kaw Valley H3 Buffer... She's our "in furniture" go-to downstairs go to rig...


"Wall-Art"...

Took the place of this rig... no current pics of the Mega/Noveske build aforementioned above yet...

FSB gang no matter what

Great write up and excellent finished product; a mid-length FSB build (aka mini-disapator?). Very, very nice jigs! I am an armature machinist with all manual machines (but I have DRO) and love tool making. You sir are a pro! You may be able to sell this as a service.

When the parts clip in Gunstruction.

You build ships in bottles too, don't cha?

Thank you sir. Engineer by trade, self taught machinist after hours. I think the second most fun part about machining things (first being the finished product) is figuring out how you accomplish it. Order of operations, figuring out rigid work holding, tool selection, determining accurate reference surfaces, building jigs, etc.

I probably could sell this service at this point. This one obviously took a whole lot of work, but now that I have the fixturing, the next one would be pretty straight forward. The toughest part was making the FSB shims. Cutting the tube with such a thin wall was puckering to say the least. I was taking super light cuts as to minimize tool pressure and not catch the material too hard and wad it up on the lathe. Was glad when I got it to size and was able cut it off.

This one could be done on manual machines, but the CNC sure helped with the barrel holding jig to make the standoffs the same size with minimal effort.

Looks like I see a KAC free float RAS chop here. Nice job. Looks even better that their original MRE rail.

I hereby dub thee "The Knight Slayer".

I concur.  And the paint is sexy.  I bet assembly was a pain, though.

Because Mk18 Mod2?

Not really. As you thread the locking collar, the rail will move and you can line up the taper pins with the holes in the handguard.

I've had several chopped rails, and this is one of easier ones to assemble.

@FONTY

Sorry for delayed response.  

Nefarious Arms dimpled the barrel.  Very well executed.

Somebody say MRE?

Nice! Love the Redi-Mag. I need one for my GWOT/Block I

I've been meaning to snag at least one more salty one for my Block 1 but things always come up that seem more important at the time. Maybe one day I'll get my life together

I want to join this club

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Long boy! What barrel and rail combo is that? Love the look with the A2 stock.

@Kuraki we need to know! A Dissy set up like this would be perfect!

This is the 15" rail I used. I milled the clearance for the FSB and taper pins myself.  Barrel and upper are FN.

I also added a QD socket and a thorntail.

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Cool!

Who's going to be the first to do a 19" rifle FSB cutout rail?

I have a 15" G mk4 that's itchin' for a 20" w/FSP.

Haven't convinced myself yet.

Almost looks like a Geissele

I wanting to get a 13” rail, and have it cut for an FSB at the mid-length location (cut similarly to the RIS II FSP). I would have it professionally cut, and installed.  Thoughts on this?


Ideally I would use a BCM MCMR, but I’m somewhat worried about rigidity. I’m also considering a Geissele MK8.

Can't speak for the BCM, but the G will be more than rigid enough.

That looks super nice.

How hard was it to get the pins back in the FSB?

The biggest thing is access to how you are going to mount the FSB. Either holes or M-LOK slots that line up with the taper pins or screws on the sides or M-LOK slots that line up with set screws on the bottom. I don't know if the MCMR allows either.