This problem is caused by the triger plate (block stop) being to short,the best way to fix this is to add metal to the block stop ( the small rounded peice at the front of the triger plate)You can also do aquick tempery fix by placeing a shim between the uper and lower block(a very thin washer around the conecting shaft of the upper block is the eaisest)but this fix also can cause the action to tighten up and is only puting off fixing it properly but it gets you out of trouble,make the washer from a soft dink can and if the action still over travels add another washer,if the action gets tight replace the washer with a thiner one