There’s a lot more that goes into it besides just the number of grams of thinsulate, such as the sole and the insulation between the sole and your feet, how well they fit, how compressed the thinsulate is, what material the boot is made out of, if they are gortex or have a similar membrane, etc.
Quick answer is yes, you will not find 1 boot that works good at all temperature ranges.
I usually use 600 gram boots for upland bird hunting. They get a little warm on the warm, sunny hot days, but they will also keep me warm enough on the days I’m walking through snow, or if I’m posting and not moving for a while. I wear them a lot for early spring and late fall fishing in the boat. And I’ll wear my 600 gram boots on occasion when deer hunting or ice fishing, but they need to be warmer days and being able to move around is a key. 400 grams is another good option for bird hunting.
I have a pair of 800 gram boots that are excellent, they are Timberland Iditarods. Probably my favorite boots. Too warm for bird hunting except on the coldest days, warm enough to cover many deer hunting and ice fishing scenarios except for the coldest days. There are a lot of 1,000 gr boots that would perform like this too I think.
When you get over 1000 grams you need to worry about the insulation being compressed too much to work very well. Insulation needs space to trap air to be effective. I bought a pair of 2000 gram boots (or something like that) specifically for ice once that Cabelas had marked way down. They’re really not that warm of boots. I had to go up 2.5 sizes from normal to have room for my toes to move, but even so the sole of the boots and the toe of the boots isn’t insulated well and my feet get cold quicker than they should. All that insulation is at the sides and top of the boots. They are a hiking or hunting style of boot, not a pack boot with rubber bottoms (which is a better style for lots of grams of insulation).
You for sure want gortex or a similar membrane in your boots. The nature of the membrane will help keep your feet a little warmer than a boot without a membrane.
A couple important things to note are making sure you have enough room for your toes to move comfortably – if they’re too tight they won’t be warm enough. And how much you’ll be moving around is a key also.
I often deer hunt in cold weather in a pack boot, the ones I have are warm and lightweight so they’re comfortable for walking, easy enough to climb in and out of treestands, etc. The rubber soles and bottoms are nice for holding a lot of insulation, keeping the wind at bay, and controlling scent.
Another option to consider for a more all-purpose boot that could be used in cold weather when you’re not moving around is the foot-heater chemical packs, either for insoles or that go under your toes. I don’t use them much myself but know some people that use them a lot and really like them. Again, make sure you have enough room in the boot for something like this if you go this route.
Good luck, I hope some of this helps.
