I know this thread is pretty old but I wanted to share my recent stovepipe problem and solution with my 715t. I bought it in '13 and it worked fine never seemed to have a problem with any type of ammo in the first couple years, but I stopped using it until last year when my daughter started shooting, IMO the collapsible stock is perfect for young shooters, but for some reason now it was getting very frequent stove pipes and FTE, which was very annoying to have to keep clearing them out for her. I tried everything I could find on the net for suggestions like the ones in this thread, ie; 10+ different types of ammo, very thorough cleaning, polished the carrier and guide, changed the angle on the guide to help the ejection, took the extractor out and cleaned/polished it as well, it was still having the same problem at least 1-3 times per mag. I couldn't find anyone suggesting a problem with the extractor spring, but I felt it was a likely cause of the problem since many times the spent case would just lay in the receiver right next to the half chambered new round, it just seemed like the extractor wasn't holding the rim of the case on its exit from the chamber. So I started looking for a new extractor spring (the tiny 3mm dia spring behind the pivot point of the extractor on the side of the bolt carrier), I couldn't even find a exact replacement online, so I ordered a spring kit from MidwayUSA and it had a spring with a 3mm diameter that was a bit stiffer, but I needed to cut it down to fit the pocket behind the extractor, turned out to be piece of cake and after it was all back together again it definitely had much more force against the shell. When we went to the range to test it out, I was a bit let down to have a stove pipe half way thru the first mag, but we pushed on and tried another mag, but this time no stove pipes, then another, and another, we probably went thru 10+ mags with no more FTE or stovepipe. We didn't even clean the rifle before we went back again the following week and shot another 10+ mags with no stovepipes at alll!!! Iwas shocked after all the problems we had to fix it with a 3mm spring. I know It may be to soon to say it's 100% fixed, but we went from multiple FTE's in each mag to none in 20, I would have to say the spring was the problem. My presumption is the extractor spring on these rifles gets weak over time (mine just went bad sitting) and just starts to fail since it doesn't have enough force to hold on to the rim. I was very close to giving up on it and replacing it with a m&p15-22, but now I'm very happy with it and I have some extra springs ready to go.
