Learning to load with a wildact is considerably difficult. My Nosler book says that there is no max case length for the 280 Ackley Improved. I understand the process to determine seat depth placing the bullet into the lands but from what I read here and elsewhere, that may not be the best thing.
Can someone give me some better advice?

Looking at the 140 NBT and Partition now as a primary go too load as defined in Nosler #5.
Again 280 Ackley Improved.

Not sure what you mean about not the best thing. Most rifles will group better if the bullet has a shorter jump. The solids like a Barnes need more.

I set mine a little different. I take a flat base bullet and seat it backwards in a fired case with the neck sized for about 1/8". Then run the case in and allow the lands to push the bullet into the case. I keep this standard (gives distance from bolt to lands). Then take the specfic bullet I'm going to use. Put the tip in the muzzle of the barrel and turn it so the lands leave a line. I set the seater up so that the line is shorter than standard by what ever distance I want that bullet from the lands. Then check to see if the bullet will fit the magazine.

I used to use the 140BT and Partition. I switched to the 140 accubond. I see no reason to need the partition at least not in a 140.

My first Jarrett rifle was/is a 280 AI that has accounted for tons and tons of deer. You will love the round but forget the dang data in the Nosler reloading manual. They (Nosler) wimped out big time with respect to load development with this fine round! Most wildcats, AI's in particular, you need to push the envelope with loads to take advantage of their extra capacity. I am not saying go stuff the case and blow yourself up, but Nosler's data was basically 280 Rem data....they were afraid to give you "real world" 280 AI data. Notice their velocities, etc....very ho hum and not indicative of what this cartridge can do. I was really disappointed. My accuracy load with my Jarrett has been 62.0 grains of RL-22, 140 grain accubond, Fed. 210M primer. IMR-4831 at max levels worked great as well as 58.5 grains of IMR-4350 with the 140 grain bullet.
I used to blow out my brass with mild loads until I was told to blow em out with bullseye powder with a quarter square of toilet paper tamped on top. I'll have to go and get the exact blow out load from my shop if you want me to. My rifle loved the nickel plated WW brass, but I switched to Norma and got better accuracy.

Just my 2 cents worth.

Forgot to add...I seat my bullets @ .02 off the lands.

quote:

RL-22, 140 grain accubond

I agree with Hank. Hard to beat RL-22 and the Nosler 140 Accubond. My 280 case has the shoulder moved forward so I end up with more capacity so I can't help you with loads.

Contact the gunsmith who built your rifle, he should be able to give you an OAL with the bullet you are going to use. If not the method used by RR340 will work well or buy yourself a Sinclair or Stoney point seating depth tool. Twenty thousandths (.020) is a decent starting place with a hunting rifle because function is just as important as milking the last few thousandths out of the group size. Be very carefull with your load development an AI cartridge does not show some of the "standard" pressure signs until you are somewhat beyond the pressures the cartridge is designed to handle.