Greetings, first time poster, long time reader...
There's some information on here and other forums about smoking meats at altitude but some of it is a little inconclusive. I live south of Denver at an elevation of 6,800 feet, and water boils at 190 for me. I'm new to smoking, and as I learn more I'll try to share what specifics I discover in case it's of benefit to others.
Last weekend, smoked a pork shoulder for the first time. I'm using a Masterbuilt Electric (yeah, yeah, yeah... Hey, I'll be the first to admit it - I'm lazy :) ). The cut was 3.5 lbs on the nose (it was a 7.5 lb that I cut roughly in half as it was only three of us sharing it).
Started out at 225, smoked with a mix of hickory. Stopped the smoke at about 140.
Internal temp got to the high 150's and stalled f-o-r-e-v-e-r. Not unexpected. Spent many hours in the high 150's to the low 160's. I eventually turned the temp up to 275 for the last hour or so, and pulled the shoulder off at about 192. I wanted to get to 200, but what can I say, we were hungry. :)
At 192 it was right on the edge of fork-pullable. I was able to pull it with a couple forks, but it wasn't the easiest thing in the world - not "falling apart" - but it was delicious and everyone enjoyed it, not dried out at all. Smoke amount was perfect, not overpowering, glad I stopped it at 140.
All told, the 3.5 lb shoulder was on for 7h45m to get to 192. The "hour for every 1.5lb" rule DOES NOT apply, that's for sure - not unexpected. I think next time rather than going longer, I will turn the heat up to 240 - since generally baking requires a little higher heat at our altitude, I'm guessing the same will be true here.
I'm thinking that I will probably do baby backs this weekend, 2-2-1 won't cut it, so not quite sure what I'll do there (any suggestions for time and temp for baby backs at this altitude?)