This was a first for me. While at the range today I was shooting my 28 inch 12guage m2. I have a tube extension on it to hold 10 rds. I figured I'd load up the last 10 and see how well I do at rapid fire. Keep in mind I had only put about 15 rds down range prior to this mag load and the gun was not that hot. Well I let loose and when complete, the bolt stayed open as it should but the barrel and chamber were on fire. I'm sure it was some un spent powder from the shells, but it could have been worse and here's why. After I put the mag tube extension on and replaced the spring, the last round never chambers. The new spring that came with the extension doesn't have enough tension to chamber that last round. So I puckered up and swatted the fire out before it had a chance to ignite the final round that failed to chamber and was sitting down below. I know I need to get a stronger spring and I won't be shooting it again until but I sure was grateful it didn't end in a major flare up. Lesson learned. Never fire a gun that you know is not functioning properly. I never would have thought that could happen.