School me on castle nuts

[Bruce3]

I was installing an Aero Precision castle nut and it cracked before reaching 40 ft/lb with Aeroshell 64 on buffer extension threads. I noticed the castle nut appeared to be Metal Injection Molded. The location of the break, it appeared to be grainy, see pics. Are there any castle nuts that are CNC'ed that are not aluminum?

Cracked Castle Nut.jpg

Cracked Castle Nut 2.jpg

[Hairball]

Torque specs are usually designed to be applied when tightening on dry threads. Using any type of grease/lubricant can change those settings by as much as 40% or so. A second issue could be the torque wrench used as it might be out of calibration. Third issue may be that you just happen to have a defective part that broke. Lastly, they do make steel castle nuts. Here is an example

https://outdoorsportsusa.com/Steel-AR-15-Castle-Nut-Tan

[kev301]

Get a pws ratcheting castle nut would be the best

[mrkubota]

40 inch/lbs and stakes. NOT 40 ft/lbs

[Bruce3]

40 inch/lbs and stakes. NOT 40 ft/lbs

Its interesting, this Army Manual has rifle extension tubes to be torqued at 35-39 ft/lbs on pg 199 but a carbine length extension at 38-42 inch/lbs on pg 200.

http://pdf.textfiles.com/manuals/MILITARY/Army%20M16A2%20and%20M4%20manual.pdf

[tabascoz28]

foot pounds, ouch. Mine have always been steel. You can also just put a 1/4 drop (use toothpick) on one thread so it stays. This way you can change it later as most people do in the years to come. I think I've been trough 3 different end plates with different QD mounts.

[NATO762]

[lexo98]

Ft. Lbs. seems really high for a tube.

[tony270]

Looks like the tool wasn't seated into the spacer slot all the way, the worker didn't keep constant pressure forcing the spanner wrench tooth against or into the spanner nut slot. Did you use an AR vise adapter to hold the lower?

[Bruce3]

Looks like the tool wasn't seated into the spacer slot all the way, the worker didn't keep constant pressure forcing the spanner wrench tooth against or into the spanner nut slot. Did you use an AR vise adapter to hold the lower?

Used a Foward Control Design Castle nut wrench with a torque wrench. The work was held in a KZ buffer tube block. Fairly certain the wrench was fully engaged with the slots and even pressure applied. The wrench slipped out of the slot after the castle nut snapped. The crack occurred right by the slot. To AP's credit they replaced the Castle But and Extension tube, marred by the slip, promptly. Repeated the process with no issue. Also built another lower using BCM Castle nut and Extension tube with no issue.

[tony270]

I was installing an Aero Precision castle nut and it cracked before reaching 40 ft/lb with Aeroshell 64 on buffer extension threads. I noticed the castle nut appeared to be Metal Injection Molded. The location of the break, it appeared to be grainy, see pics. Are there any castle nuts that are CNC'ed that are not aluminum?

[ATTACH]981627[/ATTACH]

[ATTACH]981628[/ATTACH]

You need to use a quality tool, and a brace goes inside the magazine well that claps into a vise. With the rifle secured, tighten while applying even and direct pressure in the direction of the red arrows.

Don't allow the spanner wrench to twist or torque out of the slot while pushing in and turning/tightening/setting‐torque .

The evidence are the marking left on the nut, you never had the wrench pushed into the slot while tightening (it wobbled or twisted out), the gouge markings show what happened.

A gun shop can do it for less than 20 bucks.

[tony270]

Used a Foward Control Design Castle nut wrench with a torque wrench. The work was held in a KZ buffer tube block. Fairly certain the wrench was fully engaged with the slots and even pressure applied. The wrench slipped out of the slot after the castle nut snapped. The crack occurred right by the slot. To AP's credit they replaced the Castle But and Extension tube, marred by the slip, promptly. Repeated the process with no issue. Also built another lower using BCM Castle nut and Extension tube with no issue.

I did the above while you posted this, lol. Okay you got it fixed.

[M1NM]

Its interesting, this Army Manual has rifle extension tubes to be torqued at 35-39 ft/lbs on pg 199 but a carbine length extension at 38-42 inch/lbs on pg 200.

http://pdf.textfiles.com/manuals/MIL...4%20manual.pdf

Steel nut vs aluminum nut

[Bruce3]

I did the above while you posted this, lol. Okay you got it fixed.

Appreciate the effort in the illustration! I guess my question is, how are castle nuts manufactured? MIM or CNC'ed? Aluminum or Steel?

[Bruce3]

Steel nut vs aluminum nut

Confused which is steel and which is Aluminum?