I’m curious as to the purpose of the indexing channel on the RE and the tab on the end plate after installation of a Receiver Extension. I ask because I installed a BCM Receiver Extension on a build last night and like an idiot, I didn’t stabilize the tube when I torqued the lock nut (I tightened and loosened 3 times to seat the threads). After the third time, I looked at the alignment and it was a bit off to say the least, as the tube had rotated as I torqued the lock nut. I removed the whole stock assembly, and check out the threads…sure enough, as the tube turned, the tab on the end plate pretty much removed about 3-4 millimeters of the threads on the tube. I reinstalled the RE, and this time held it tight, as there were no threads to engage the tab on the end plate and prevent it from rotating as I torqued. It worked, and the stock assembly is straight now.
My question is; does it matter now that the castle nut is torqued and end plate staked? Does the indexing channel and end plate tab serve much of a purpose to keep everything straight AFTER the Receiver Extension is installed, or are they only there to aid in installation? My though process is that if the gun took a fall on the stock hard enough to twist the RE, the same thing would happen anyway (The tube would twist and the end plate tab would destroy the threads). I have another BCM RE inbound as I type this just in case. I feel like an idiot, and lesson learned for next time. Thank in advance all
It looks like he put the Receiver End Plate on backward. I’m not talking about the protrusion on the end plate that mates into the lower receiver. I’m talking about the little indexing tab that rides in the channel on the Receiver Extension that prevents it from rotating when the Castle Nut is torqued.
He did, it’s in the comments that he realized it after shooting the video and corrected it later. I thought that was funny though.
But I don’t understand what you did. How did that tab damage the threads? It should have stayed in the channel on the RE?
All these things serve a purpose and work together. I wouldn’t loose any sleep over the threads, but if you ever find that the RE has rotated, perhaps change it out then. Chances are that You’ll never have any trouble out of it.
Next time you install one go ahead and slip the stock on and have someone apply torque in the opposite direction using the stock.
Sometimes you need to work with what you have and I know many people use a mag well vise block (myself included at times), but the most correct way to do the castle nut to avoid issues is to clamp the receiver extension and not the receiver via holding it down or placing it in a mag well vise block. If you do use a mag well vise block just be careful. Those who do it a lot will probably have no issues but those who are new to it have been known to create issues or break things.
You can lock the tube in a vise (with copper vise jaws as an example) and then torque the nut. I also show people in the class how to use the buttstock on the tube to help hold the tube and stop it from moving.
It is amazing, of all the receiver extensions I have installed over the past 10 years, I have never had one that wanted to rotate when I was tightening the castle nut, nor did I have any issues with end plates. It is not rocket science. You either know what you are doing or you do not. If you do not, then you can screw it up.
Agreed, it’s common, a weak area in the design as far as assembling it goes. Doesn’t seem to be an issue once it’s together, even when the RE’s keyway is completely buggered up.
I think Renegade has gotten very lucky for the last decade. I definitely understand how to perform the procedure as well as how to use the tools I use. My dumb ass just didn’t think to hold the RE in place…I figured the tab/channel would do that. I fully comprehend now that 40 ft/lbs of rotational force is enough for 7075 aluminum to be defeated by steel. I’m embarrassed honestly. I just wanted to make sure that it’s good to go when assembled and didn’t require the tab/channel to remain straight after the fact. It makes sense that it’s more about the tension between the Castle Nut and End Plate.
On a side note; I got my MOACKs Plain a few weeks ago Ned. It’s awesome! Thanks again
This is an area that I’ve buggered a few in my time (and I always confess this in classes when we get to this area ). You have a keyway cut into relatively soft aluminum, and then half the aluminum keyway’s side area is removed via the threads, then a key to fit into the keyway that is steel, but A) not very long (ever notice how Woodruff keys are like 4X longer than wide?), and B) very likely the key’s side area is reduced by the fact that it’s a stamping and as happens in stampings, the steel has “rolled” a bit before the part was sheared out. The result is very, very little bearing area, key-to-keyway. No wonder it’s so technique-intensive to not gnarf it up.
). You have a keyway cut into relatively soft aluminum, and then half the aluminum keyway’s side area is removed via the threads, then a key to fit into the keyway that is steel, but A) not very long (ever notice how Woodruff keys are like 4X longer than wide?), and B) very likely the key’s side area is reduced by the fact that it’s a stamping and as happens in stampings, the steel has “rolled” a bit before the part was sheared out. The result is very, very little bearing area, key-to-keyway. No wonder it’s so technique-intensive to not gnarf it up.