This is probably not the issue but make sure the recipes are written for the Instant Pot specifically, not stove top pressure cookers. Instant Pots cook at 12psi as opposed to stovetop which are traditionally 15psi and cook a little faster. Still, that shouldn’t account for that much disparity and it seems like more recipes are oriented towards Instant Pots than stovetop these days.
I found the America’s Test Kitchen pressure cooker book to be decent enough but it’s very clearly intended for Instant Pots based on the technique and how overcooked the results are when I use my stovetop. They definitely have a corned beef recipe so maybe that would be a useful starting point…?
Oh, also if you do find the corned beef more tender than you anticipated it should still firm up decently if you cool it down. I find corned beef shreds when I let it go too long but even so if you slice it when cold it retains its shape well enough and if you want you can still reheat it over steam briefly for a hot sandwich. I would recommend this route as undercooked corned beef is serious shoe leather
No veg and sliced for sandwiches, I’d try it at the 60 minute mark and cool and slice per @WireMonkey notes. I agree that undercooked braised proteins can be troublesome. Chilling and slicing will achieve what you want.
It’s available now as an ebook from LA Public Library so I checked it out and looked over the recipe. It’s a bit fiddly but the overall cook time for a 3-4lb roast is 1.5 hours with a natural release. That seems a little long even for an Instant Pot but there ya go.
I would note that the cook time for vegetables was 12 minutes which is pretty bonkers even for an Instant Pot so maybe they overestimated the time needed regardless of the model used. The one time I tried it the cabbage turned out like wet tissue paper. Maybe I need to rethink this book generally…
I wouldn’t use the Instant Pot for any recipe with multiple steps or with ingredients that should cook at different temperatures or for different lengths of time, like beef and cabbage. People who think it’s great for all kinds of things must not be very fussy about cooking.
I’m about to cook the corned beef. I went to the Instant Pot website to see what they suggested.
70 minutes for slicing, 90 minutes for falling off the bone
Numerous recipes I ran across went with 90. After thinking about it, I’m going with 90 minutes. Don’t want to risk toughness. Rather go a little further than not enough.