So I took my 870 out yesterday amongst other goodies for a long range day extravaganza. I got about 80 rounds through my 870 until a round was fired (last in the gun). There was a bang, and then the sound of metal hitting gravel. A split second later and I noticed that the factory extended mag tube, spring, and magazine cap/ union nut was on the ground. Upon further inspection it appeared that some threads on the mag cap -- not from the portion of the extended of the mag tube, but from where the extended mag tube attaches to the "standard length" mag tube are sheared off. I should mention that I have a GG&G front sling attachment mounts in between the mag cap and the "standard length" tube. I am thinking this problem can be attributed to the fact that the GG&G front sling mount does not allow all of the threads of the mag cap to be utilized, due to the extra space of the sling attachment itself. I have been looking around for some aftermarket type mag caps that are not so -- I suppose, inferior. Any suggestions?