Heat-treated, phosphate-finished castle nut for AR15/M4 carbine buffer tubes, with large wrench notches and small notches for staking. Made in the USA.
$11.74
Available on back-order
The Magpul Heat Treated Castle Nut (MAG817) secures the receiver extension (buffer tube) and end plate on AR15/M4 pattern carbine lowers. It is heat-treated steel with a mil-spec manganese phosphate finish, has large notches for an armourer’s castle-nut wrench and small notches so it can be staked to the end plate to prevent loosening. Made in the USA.
Does it fit commercial buffer tubes?
It is specified for AR15/M4 mil-spec receiver extensions; check your tube’s thread before ordering.
Should the castle nut be staked?
Yes, staking the small notches to the end plate is the standard way to stop the nut backing off.
Is it still in production?
This part no longer appears on magpul.com; 3GT’s listing is for remaining stock and supply is not assured.
The Magpul Heat Treated Castle Nut (MAG817) secures the receiver extension (buffer tube) and end plate on AR15/M4 pattern carbine lowers. It is heat-treated steel with a mil-spec manganese phosphate finish, has large notches for an armourer’s castle-nut wrench and small notches so it can be staked to the end plate to prevent loosening. Made in the USA.
Does it fit commercial buffer tubes?
It is specified for AR15/M4 mil-spec receiver extensions; check your tube’s thread before ordering.
Should the castle nut be staked?
Yes, staking the small notches to the end plate is the standard way to stop the nut backing off.
Is it still in production?
This part no longer appears on magpul.com; 3GT’s listing is for remaining stock and supply is not assured.
| Brand | Magpul |
|---|---|
| Model | Heat Treated Castle Nut |
| Part number | MAG817-BLK |
| Fits | AR15 / M4 carbine receiver extension |
| Finish | Manganese phosphate |
| Country of origin | USA |
Reviews
There are no reviews yet.