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View Full Version : .300 BLK / Armalite monolithic



Ned Christiansen
02-05-13, 21:40
About a year ago I took a customer's AR pistol and changed it over to .300 AAC Blackout. Used an Armalite SPR-1 monolithic upper and a Satern barrel.... it worked and shot very well.

I asked him to send it back recently to put an adjustable gas block on it-- I got a few from Paladin Machine and I thought they were very nicely made so I thought his BLK might be a good place to try one out.

Barrel with gasblock installed. It is made with two 10-32 set screws to hold it on the barrel-- as is my practice I used them to hold the thing in place while I drilled for a cross pin. Same deal with the gas tube-- the instructions are cut .900 off it and then it's held in the block with two set screws. I put two .078 roll pins in place to make sure it stayed put when the screws come loose. The rotating adjustment shaft is held in place with a snap ring. The whole thing is heat treated but is on the 'tough" side rather than the "rock hard" side, so I was able to take a little weight out of it-- maybe 1/2 ounce, big deal. It is not heavy to begin with. I had to do a lot of machining and fiddling with the Armalite unit to make room for the gas block-- it is a little larger than the lo-pro unit I had used originally.
http://farm9.staticflickr.com/8089/8448658741_6936ec9352_h.jpg

Close up of it all together.
http://farm9.staticflickr.com/8334/8449743498_4f31378ef2_h.jpg

The muzzle device is a simple cone flash hider made out of titanium. I took one web out of the rail for access to the adjustment. Worked out about right, you can get to it but it doesn't stick out anywhere.
http://farm9.staticflickr.com/8360/8449743984_f0357f51e3_b.jpg

ReaperAZ
02-06-13, 11:42
Nicely done. That thing sure looks the part with that muzzle device on it.

Ned Christiansen
02-13-13, 14:11
A couple more pics.....

First one: Carrier insert which contains (pick one):

A. Rack-and-pinion regulated reciprocating tantalum counterweight dampened in gas-charged atmosphere (nitrogen, argon and flatulus). Gives a rate of fire that is not slower, not faster... but just right.

B. A little Delrin cup containing a couple tools for working on the gun.

http://i368.photobucket.com/albums/oo125/NedChristiansen/DSC01792.jpg

http://i368.photobucket.com/albums/oo125/NedChristiansen/DSC01787.jpg

Here's the cup removed and tools spilled. One is for removing the flash hider. It fits into the slots on the end and then, using the slot at the rear of the bolt carrier as a cheater, you can remove or install it in the event you want to change to something else. Otherwise the fore end has to come apart so the FH's wrench flats can be accessed.
http://i368.photobucket.com/albums/oo125/NedChristiansen/DSC01786.jpg

And-- the gasblock adjustment tool in use. Gasblock adjustment without a tool is easy-- until you've fired a mag through it. I hate having to use a tool to do it but I did not want anything sticking out-- like a big knob or lever-- to snag on things or get broken off. Big green dot= wide open, subsonics. Small green dot= reduced gas passage for supersonic ammo. Red dot with "X", closed. Tool uses a cartridge or case as a "T" handle.

http://i368.photobucket.com/albums/oo125/NedChristiansen/DSC01789.jpg