Every now and then, customers will bring to us their M16 and M4 rifles with stucked empty shells inside the chamber of their barrels. In some instances, the empty shells have ruptured at the base. In other instances, the empty shells got split in half and the front half gets stucked inside the chamber. Others would have dropped primers, etc.
Here are the following possible causes:
The headspace of the chamber is incorrect. For this, we find the chamber reamed for the caliber .223 and in other instances, the chamber of an old barrel is already loose. Sometimes, what we do is to ream the chamber for the correct 5.56 NATO caliber but this is after removing (destroying) the barrel extension and then refacing (shaving off) about 2-3mm of the chamber lip. Then we ream the chamber for 5.56 NATO. But if the barrel is already too old, we just advice the owner to replace it.
But the real focus of this topic is the DANGER OF USING RELOADED 5.56 NATO AMMUNITION. In the picture we have attached with this post, it shows a reloaded ammunition which ruptured at the base. When the rifle was brought to us, the bolt assembly cannot be retracted and we had to literally dismantle the whole rifle to disengage the bolt head’s lugs from the barrel extension. After we were able to retract the bolt assembly, we were also able to extract the empty shell (as pictured) and saw it got ruptured near the base. Luckily, the back pressure found its way in the magazine and deformed it (see picture). Now what are the possibilities?
Overcharged, e.g., pistol powder was inadvertently used. Pistol ammo powders are faster burning than rifle ammo powders.
Weak case from several times of reloading.
Case mouth flow into free-bore causing bullet exit delay due to pinching of the case mouth against the bullet. This defect can drastically raise pressures.
All cases stretch when fired and have to be re-sized and trimmed before reloading. If the reloader does not use gauges, then this is a big problem.
So what is the moral lesson of this story? Don’t be STINGY. Buy factory-loaded, brandnew, never-been-fired ammunition for your 5.56 NATO rifle. The example and the pictures we shared with you is a ”mild” accident only. But it could be worse. Your rifle may blow-up on your face and damage your eyes and hands. Awful !!