Like most on this thread I had similar results with a 7mm 154 gr SST. I still use them for deer and antelope but greatly prefer to step up to the 154 interbond which I have had great luck with on Elk.
I upgraded to a vac master 215 chamber sealer last year and love it. Yes, they are expensive, but they are a commercial product and meant to high volume use. Between my animals and friends I generally package around 500 pounds of meat a year.
I had used several traditional out of chamber...