Michael from United States, CA Public Profile

I'm really happy that I saw this ratcheting castle nut system mentioned in a TFB article and was able to find it here on OpticsPlanet! I included this ratcheting castle nut on my first two builds, where there was a very high probability that I would go full-on "adult lego" and end up swapping in/out a lot of parts. By the time I got my lower Cerakoated and assembled with the rifle-length adjustable buffer tube I eventually swapped in, I had assembled and disassembled the whole lower four times. Not only was this easy to assemble and disassemble with just an armorer's wrench, this holds securely without staking, and was also able to be Cerakoted to match my lower without interfering with the ratchet system. This thing is awesome, I love it!

I purchased two CMMG lower parts kits: this Gunbuilder Kit and the complete lower parts kit, I've had problems with parts from both kits being out of spec. In this Gunbuilder Kit the included bolt catch wouldn't hold the bolt on my gun open, both when I manually pressed down on the lower half of the catch and when the magazine follower engaged the catch when empty. It occasionally hold the bolt open for a few seconds before slipping off and allowing the bcg to slam forward. I swapped out the bolt catch from this kit with a $5 replacement I picked up at a local gun store and the new catch works just fine. In the other kit (complete LPK) the fire control group was so out of spec I had to modify it to get the hammer to release upon pulling the trigger (it was totally locked up), the safety selector also didn't sit straight in my kit. Other parts are okay. From here on out, I will not be buying anything from CMMG. I'm happy to spend more for parts that actually meet spec out of the box.

I've used these for two builds so far, they work as-advertised. I prefer to buy the extension tube, spring, and buffer together for basic builds so I don't need to do the leg work or forum research to find an optimal combinations for a given rifle (you also tend to get a better deal in my experience). I did swap a third one of these out for an anti-tilt buffer on a lower that I wanted to pair with a piston upper, but that is sort of a special case where the upper was has a notorious failure mode to with special components. I'm happy with this extension tube set.

I was expecting better from CMMG... gets the job done but you'd be disappointed in yourself if you paid full price for it. The pistol grip feels really cheap, the safety selector lever and arrow are offset by about 15 degrees (to the point were my wife looked at the finished product and asked me if it was really on "SAFE"), and worst of all the disconnector and hammer are so rough out of the package that the trigger would absolutely not fire when pulled. I took it apart three times to double and triple check that I didn't mess up the spring orientation, I didn't, just super rough surfaces. I worked out the roughness by pressing down hard on top of the disconnector with a punch before each trigger pull and then working the trigger while guarding the lower from the hammer with my had (repeat about 200 times until your hand is sore and it will wear down the roughness such that it eventually resets properly). I'll definitely be going with a different LPK brand when I build out the lower for my wife's rifle.