Castle nut help

DirtySCREW

I am Negan
Charter Member
Life Member
Multi-Factor Enabled
Joined
Dec 18, 2016
Messages
9,188
Location
NC
Rating - 100%
4   0   0
I'm trying to tighten my son's Castle nut to 40 ft lbs on his newly build AR.

The buffer tube keeps twisting as I attempt to torque it.
I'm not an octopus and don't have 8 hands to hold everything.

Lower is in a mag vice block. Castle nut is screwed down by hand all the way.
Buffer tube is straight. When I apply the castle nut wrench with my torque wrench set to 40ft lbs...the buffer tube twists clockwise.
Why...and how do I fix it so I can properly torque the nut.
I'm using a pos DPMS WRENCH.

HELP


DS
 
Last edited:
You should have the stock end plate that engages with the lower and the buffer tube to keep it from turning. Plate shown in red below. If the buffer tube is turning with the plate installed properly, you have a problem with the plate or the buffer tube.

Is your plate turned so that the bulge is set into the recess of the lower? If your plate is turned around (bulge out) it will allow the buffer tube to turn.

4A3757C3-0B4A-4616-8BAF-11DBBB0667CE.jpeg
 
Last edited:
Isnt the endplate supposed to have a key in it to prevent this?
Right?

I’ve never had one turn because the endplate has a tab that fits in the indention on the receiver.
 
I got it fixed guys.

Yes buffer spring detent was installed... everything was like it should be.
However when I went to torque the castle nut, the last 10ft lbs or so rotated the buffer tube slightly....10 degrees?
My OCD wasn't having that!

So...I put the stock on and shortened it up on the buffer tube so I could hold it and counter the Mrs. as she torqued the wrench.
It worked out...stock is straight now.
Gun is 99% complete....just wanting on a Magpul rear sight to arrive on Monday!!

IMG_20200104_173653484.jpg

Thanks guys....just got really frustrated as I never had that happen before. It's an Anderson lower....PSA upper. ...

DS
 
Funny, I just switched out the end plate on my new build for the same reason. The lug was too short.
 
Hopefully y’all are tapping the selector spring hole and installing a screw at some point in this process. Makes removing it in the future much less frustrating.
 
Hopefully y’all are tapping the selector spring hole and installing a screw at some point in this process. Makes removing it in the future much less frustrating.

Stop reading me mind. I was just googling what size tap and grub screw I need lol
 
Stop reading me mind. I was just googling what size tap and grub screw I need lol
I bought a box of 100 screws and have at least 90 left.

If you want to hold off, I’ll bring it whenever we meet up again and you can use it on the spot.
 
Stop reading me mind. I was just googling what size tap and grub screw I need lol
4-40 as short as you can get them?
I keep a little tap and die set and a bunch of screws my gun tool box because why not?
what i DON'T have in there is some side cutters to shorten up the springs...
 
Those nuts have a torque spec? Huh.
so they say. I've found that "tight enough" works fine until you put enough torque (via sling) on the stock that you manage to rotate the tube. then you're boned.
Now i make it "tight enough" AND solidly stake my end plate to the castle nut
 
so they say. I've found that "tight enough" works fine until you put enough torque (via sling) on the stock that you manage to rotate the tube. then you're boned.
Now i make it "tight enough" AND solidly stake my end plate to the castle nut

A drop of blue locktite does it for me.
 
Back
Top Bottom