Just wondering about the suitability of the 6PPC as a deer cartridge. One I'm looking at (a Sako) has a 1:14 twist. This would limit it to 70-grain 6mm bullets, I'd guess. Anyone here with experience with light bullets in a 6PPC when deer hunting?

6PPC is the benchrest version of a 6ARC and people shoot deer with those.
Here on the fire jack wagons shoot deer with 222 Remington's with 1-14" twist
pick a good bullet and keep the distance reasonable and it will work fine

I have a Sako Vixen in 6ppc. I got it from my dad and he had it built to be as light as possible. It has an 18" barrel and a fiberglass stock. He has taken deer and antelope with it. We are usually close or less than 150 yards when hunting in those few places and using 70 grain bullets. I’m a lefty and usually shoot it at the range now but I carry it to mess around sometimes when hiking and such. It’s uncomfortably light. Kind of feels like a kids toy. I haven’t weighed it lately but in the past I remember it being right around 5 pounds. It’s getting a new barrel because the old one had a lot of rounds through it and was opening up real bad. I hope to have it back soon.

I’ve got a 6PPC my ex used to tag a nice antelope. Used light copper bullets (GS Custom). Worked like you’d want it to.

I imagine that, with the 1:14 twist, I'll need to stick to 70-gr. bullets and lighter. Is there a good 70-grain 6mm. deer-hunting bullet available?

Not really, I'd be looking for some flat base 80 grain bullets. I've used the 70 grain Noslet BT on white tail and pronghorn but I kept the MV lower 2800 fps or there about, and tried not to shoot anything under 100 yards. I shoot a 6X222 RM with a 1:12 twist and it loves 70 grain bullets.

I had a 6PPC Encore barrel with a 1-10" twist about 20 years ago. It would stabilize 85 gr. Sierra BTHP just fine. I killed a few mule deer with it, nothing beyond 250 yards. But it worked just fine.