My neighbor and I have the Remington Ultimate Muzzleloader.
I am using the recommended use of Triple 7 powder and the supplied 250 gr accutip bullet. By mixing 50 gr Triple 7 and the 60 gr magnum Triple sevens was able start at 200 gr and work down. The best load for this rifle is three 60 gr magnum pellets for 2346 fps @ 38 degrees. Using Fed 215 primers.
Some observations:
After shooting the rifle once it is extremely difficult to load second round without cleaning crud ring just above where pellets sit. I clean after every shot and it shoots 3/4 MOA.
This rifle has the laminate stock. Front swivel stud is a wood screw. The channel for the ramrod offers very little wood for the wood screw to hold. IT WILL PULL OUT! I made a short plate and tapped it for a machine screw threaded stud. Plate has to be somewhat thin to for ramrod to clear.
Will be using mine on a NM cow elk hunt next week. The laminate stock is very slippery and even worse with gloves so I added some strips of non slip grit adhesive. A small strip around grip and one on each side of fore end.
You cannot use Blackhorn 209 powder with the factory breech plug. It will erode the plug and Remington won't warranty it. It is designed to use pellets only.
My neighbor also has a Rem Ultimate Muzzleloader. He had Arrowhead's ignition/breech plug system added. He is using Blackhorn powder with the Scorpion gold 300 gr bullet. (
https://www.harvestermuzzleloading.com/products/scorpion-pt-gold ) As I see it besides getting higher velocity Blackhorn doesn't make that crud ring allowing for easy loading and multiple shots without the need to swab of bore between shots and no loss of accuracy.
Based on the results of my cow elk hunt I will either stay with the current breech plug or spend the money to upgrade to Arrowhead's system.
https://www.arrowheadrifles.com/product/uml_replacement_plug/