Last Summer my neighbor, his son and a couple of his friends were shooting on the back side of my property. Laura (wife) yells to me while I was working in my gunsmith shop telling me that I better get to the range because two of Warren County’s finest had shown up. While the Sheriff department is great, they don’t normally just stop in to be friendly. The deputies were very nice and said that they received a call from an anonymous person who was worried about all the shooting. The officers said their concern wasn’t with noise but rather where the bullets were traveling, more like where they were stopping. By the time I had arrived they had checked out my backstop and were satisfied that the bullets had a nice place to come to rest. I explained that I had a gunsmith business on the property and that I had jumped through all the local government hoops, including getting my backstop approved by their boss (Sheriff) in order to receive my business license. We had a pleasant conversation, including as many names that I could drop as possible, soon they went back to doing whatever deputies do.
Since I was already at the range I asked my neighbor to introduce me to his friends. While I was watching with the Good Lord self-equipped hearing protection we all are given at birth (fingers in my ears), I noticed one of the neighbor’s friends (let’s call him Sam) shaking his gun sideways and rooting around inside the ejection port with his fingers like a hog looking for that last piece of corn. I offered my services to him (the free kind) in hope that he would stop shaking the gun. My neighbor reminded him about my gunsmith business to distract Sam from his gun shaking frenzy. Upon recognizing the truth in my neighbor’s statement, Sam’s convulsion immediately ended, and I was handed his AR-15. (Oh no, not one of those!!!) He explained to me not many shots were sent down range because of the malfunction. When I peeked inside, I found the nose of bullet had stopped against the end of barrel extension and the bolt was laying on top of the case having produced enough force when closing to bend the case near the neck. At first it appeared the bolt had stripped the round from the magazine but lost purchase before the cartridge could be shoved into the chamber. The bolt was wedged tight along with the magazine, and no amount of rooting around with fingers was going to set the poor cartridge free; but some brute force would. I grabbed the charging handle and yanked on it as hard as I could: three times. Finally, the bolt came loose, and I locked it in the open position. I turned the gun with its ejection port face down, the unhappy cartridge fell out, and I removed the magazine. I couldn’t see anything obviously wrong, so I reinserted the magazine. I handed Sam the rifle and watched him release the cocking handle to manually feed the next round into the chamber. Without a word Sam stopped, turned around, and handed me the AR. The jam looked just as it had before. He asked me if I could fix his gun for him. I gave it another field evaluation, but no cause was evident. I told him that I would have to keep the gun and there would be a charge. Sam agreed. He said he had just purchased it new along with a bunch of ammo at a gun show, and he just wanted it work. I told him to follow me to my office to do all the unsatisfying but necessary administrative stuff.
When I began working on the rifle, I found the problem I was expecting. It is claimed by experts to be the most common feeding issue for an AR-15. What I found was barely noticeable even with a light shining where the bullet had stubbed, but using a dental pick, I could feel the leading edge of the barrel extension sticking over the top of the frame feed ramp; it is required to be slightly behind it. There is a formula for the relationship between the two feed ramps, but I won’t get into it here. Simply put, the actual problem was the tip of the bullet was stubbing (sticking) on the leading edge of the feed ramp of the barrel extension. This sudden stop caused the base of the cartridge to be forced off the face of the inertia laden bolt, allowing the assembly to slide over the top of the cartridge (known as override) until the case stopped its forward momentum bending the case near the neck.
The solution was to reshape the barrel extension feed ramp, so the edge of the ramp was behind the frame feed ramp, allowing the bullet nose to jump onto the extension feed ramp somewhere beyond the leading edge. To perform this task, I needed to pull the barrel and the extension, so I could get to the ramps physically and visually to recontour them. Getting to the barrel was time consuming, not because of the design of the AR-15, but because an unscrupulous salesman at the gun show where the gun was purchased saw someone new to the AR-15 world and convinced Sam that he needed to be ready for the apocalypse. Sam’s new AR-15 had a least one of every conceivable attachment possible (slightly exaggerated, but not much). I took me quite a while to strip the gun down, just so I could just get to the place of normal disassembly. I finally removed the barrel and looked at the ramps. The problem was obvious.
The leading edge of the barrel extension ramps were not ground to a knife edge as it should have been. What I thought was a barrel ramp edge extending over the top of the frame ramps was just improperly cut feed ramps that were left too thick at the leading edge. The barrel ramp was behind the top of the frame ramp, but since the edge was too thick, the nose of the bullet was getting caught on it. I reshaped the barrel extension ramps (AR-15 has two) to create a knife edge. This actually put the edge about ten thousandths of an inch (0.010”) behind the top of the frame ramp. Perfect! Grinding to a knife edge caused me to change the angle from the bottom of the ramp to the transitions into the barrel extension mouth. After the recontouring of the extension ramps they were polished, and the rifle reassembled (Sorry,no pictures I wasn't planning on using any of the pictures in the write up.) I tested the AR by emptying a 15-round mag through it. The black rifle worked flawlessly. The customer picked the gun up and was very pleased. I hope this long post, but short article will shed some light on probably the most common feeding problem for the AR-15.
A Little More to the Story.
Knowing Sam was a new to the AR-15, and maybe the shooting world in general he needed to be warned not to shoot 5.56x45mm ammo through his Frankenstein AR. The reason for the warning you will have to wait on because in my next article I want to explain what a “Frankenstein AR.” and if it is a monster or not.
