Soldiers, word from the field is that some of you are reporting M16 and M4 bolt damage. The bolt locking lugs are cracking, breaking off, causing weapon stoppages, and creating a risk of injury and weapon damage.
There are warnings in every weapon technical manual (TM) telling you to keep your ammo clean and dry. Don’t
be fooled by the incorrect field-expedient guidance that says a little lube in your chamber and on your ammo helps the weapon perform better!
Here’s why you don’t
lube your ammo. Whenever you fire your weapon, the brass cartridge case expands to fill all voids between the cartridge and the chamber walls to keep the hot gasses in. For a quick two (2) milliseconds, the brass cartridge case binds with the chamber walls as the bullet leaves the barrel and the chamber pressure drops to zero. The brass case then returns to nearly normal size and is extracted from the chamber.
If you put lubricant in the chamber or on the ammo, then the cartridge case can’t bind with the chamber wall as intended for the weapon to reliably function, increasing force on the locking lugs.
Here’s what you can do to keep your weapon operating properly.
- Keep your ammo clean and dry as stated in your weapon’s TM.
- Inspect your weapon every time you clean it after firing.
On your bolt, look for any obvious missing parts, like the missing locking lug in the image below.
Look for missing parts on bolt
Also, look for hairline cracks at the base of each bolt lug. An easy way to see the hairline cracks is to follow these steps.
- Put a drop of CLP at the base of the lug.
- Then try to wiggle the locking lug while watching the lube.
The oil will seep into the hairline crack and make the crack easier to see.
Bolt with a crack
Squad leaders, teach this technique to your Soldiers. You’ll find the inspection listed in the AFTER OPERATIONS PMCS in TM 9-1005-319-10 (Aug 18, w/Ch 2, Apr 19).
Always inspect your whole weapon with attention to detail. Report any defects to your NCOs and the unit armorer to get it repaired. And remember that the serviceability of your weapon is your responsibility. Your life could depend on it.