Sesshoku wrote:Here is the video I shot today. I have each clip in regular speed then a short replay slowed down to 10%. I sure hope this shows someone what the heck is going on. Well, besides my bad form.
http://youtu.be/bsc5XOJLucQ
At the end of the clip, I tried to show the gouge in the brass of the live round after it got jammed. It doesn't show up well partly because it was the smaller gouge of the three times it happened. The first two dented the brass a good 1/8th of an inch.
I looped on that FTE about 20 times and it looks like either a gritty or weak ejector plunger, or when Bushmaster milled the ejection port, they milled too little or left an inward facing rough edge around the rim of the opening that's catching the case occasionally. My primary feeling is the plunger though. If it were me, I'd drive out the retaining pin, remove the plunger and inspect the spring. Stick a tube from a spray can down in the hole and give it a squirt to dislodge any possible debris. Alternately, polish the plunger on a wheel (no simple task) or with a dremel and a polishing fob. The plunger spring tension should be so strong as to almost be impossible to push it all the way in with the tip of your finger. When it successfully ejects a case, how far does the case fly away from the gun? If it's a ways off, then perhaps look at the ejection port milling job. Look for brass smudge or actual buildup where the cases are possibly hitting. Lastly and I know it's expensive burning through ammo to troubleshoot, remove the magazine before each shot for the number of shots it typically takes for an FTE to occur and see if they stop. The mag may be sitting a little too high and is deflecting the cases upward as they travel back. Then when they clear the barrel extension and begin to flip out, that upward deflection makes them run into the top of the ejection port.
Hoot