I have a custom 28 Nosler and I can tell you, they can be picky finding the right combo of powder and bullet. I have tried H1k, Retumbo, RL33 and IMR8133. Mine seemed to like RL33, however, this powder is temp sensitive and like others stated above 80 degree's and you developed a max load in the winter, you will see a spike in pressure and bolt stick with a possibility of popping a primer. It is very dirty and will require cleaning every 20 to 30 rounds. I will also warn you chasing those tiny groups in this cartridge will eat your throat, it definitely is not a target rifle, if you do not have a borescope, get one, you can find one for 50.00 on Amazon called Teslong, very good scope for the price. I noticed on my Brux SS barrel, I would see about 1/8 inch of throat erosion every 100 rounds. My suggestion, pick one bullet you want to use for this rifle, once you determine that part, work slowly with the seating depth first with the powder you want to use. I would start at around the minimum powder charge and run a seating depth test like Berger recommends with a hunting rifle, except I would keep it at 3 shot groups max per seating depth. Once you find the correct seating depth your rifle likes, say under .75 group, then work on powder charge, you should see it at minimum holding what you found on seating test, then it will or should open up as you go up in powder and then start back to closing up, you may see a couple of nodes that are good in the powder range. Groups will open then close then open again and maybe close by the time you hit max charge. I would suggest using a Chronograph on all your testing, this will give you a good idea on what your combustion looks like on each charge, you should see ES/SD go up and down through all of them, you will probably see some that have large spreads that shoot great and some with small spreads that shoot crappy, but you should find one that comes together with good group and spread. Once you find a node, you need to see if you can duplicate it. If you can then move out to 500 yards and test it. Go at slow, don't swap bullets, powder or primer stick with one combo. I will also say, since this is a factory rifle, it is probably setup on SAMMI specs and probably shoots the 160gr class bullets very well. Good luck, but keep an eye out on round count, depending on how hard you push it, your barrel will last anywhere from 700 to 1100 rounds, but more likely below 1000. The powders that are hard on throats are RL33 and N570, H1000 is probably going to be your coolest burning. I have mine shooting 169HH at little over 3200fps at around .650 on size, remember this is a hunting rig, so anything below 1 MOA is awesome, don't sweat it to .50 or less. You should be most concerned with the first cold bore shot from 100 to 1000 yards, this will be a real hunting scenario.
