http://rossrifle.com/forum/index.php?topic=1116.0
http://rossrifle.com/forum/index.php?topic=1116.msg7434#msg7434
here is a link on exactly this topic from the Ross Rifle Forum.
I have formed 280 Ross from both 300 H+H and 375 Ruger.
Both are a bit of an involved process.
here is my post on re forming 300H+H from the Ross Rifle Forum copied below
I haven't used 375 Ruger as a parent case for 280 Ross. My first attempt at loading for the 280 Ross was just this month. I picked up some new Hornady 300H+H brass to use as the parent for the 280 Ross cases.
I have reloaded for a long time including for a wildcat cartridge (340Gibbs) that I need to fire-form from 30-06. Followed a similar process to make 280 Ross. I had initially just resized the 300 H+H and stoked the brass with light charges. Then I thought better of it and pulled the bullets and started over.
Here is what I did to make 280 Ross from new 300H+H.
1- trim 300 H+H cases to 2.6 inches
2 camfer case mouth
3 install 30 cal expander on the decapping rod in the 280 die
4 lube case and inside case mouth- run it through the die - you will have a 280 ross case with a 30 cal neck
5 install 28 cal expander on decapping rod in the die
6 re-set the die so it is about 1/8 to 3/16 inch higher in the press- should be a gap of 1/8 to 3-16 between shell holder and the bottom of die
7 run 1 case through the die again- the neck will be 280 for about 2/3 to 3/4 of its length and then will remain at 30 cal just above the shoulder- This bump, in essence a false shoulder, is what will hold your case firmly between the bolt face and the chamber when fire forming. Feed a case into your rifle (unprimed). You should feel resistance but bolt head should turn and lock. If not, re-set the sizing die lower(reduce gap between die and shell holder) until the brass will feed into the chamber with resistance and bolt will lock up.
8 Re size the rest of your cases.
9 prime cases- load with 13 grains of 700x powder-
10 fill remainder of each case right up to the case mouth with cream of wheat- stuff a wad of Kleenex in the end to hold it in there
11 go to range . carefully feed each case into chamber and fire down range- you now have fire formed brass
12 Trim, resize and reload your brass again as you normally would with a starting load ( I am using 52 grains of IMR 4350 behind 150 gr bullets)
13 fire these rounds
14 anneal, trim, re-size and reload
I have seen different suggestions on how to go about fire forming cases. Some suggest trimming parent brass to length, resizing in the 280 die, stuffing a long bullet like a 175 gr Hornady RN into the case over a starting load and seating the bullet far enough out to jam into the lands. This process will work as well but I have a preference for the Cream of Wheat method.
The one thing I noticed about the 300H+H brass is that it re-sized very easily because of the similar taper of the case walls as compared to 280 Ross. Some have used 7mm rem mag as parent but it ends up too short (2.5 inches). Others suggest 300 Win Mag. Easy to get and cheaper than most because it is so common. But there is a lot of case to squeeze down to 280 Ross dimensions.
I have a 280 Ross die with a crack in it which I am sure is the result of resizing something really big into 280 Ross.
As stated at the outset, I have no experience with using 375 Ruger to form 280 Ross. Hopefully your 375 Ruger brass will re-size easily. Once you have it squeezed down to a 280 Ross case, the rest is pretty easy.
and another post on reforming 375 Ruger into 280 Ross
Fellow .280 Ross reloaders:
Here is my formula for forming .280 Ross cases from .375 Ruger cases using Imperial Sizing Wax.
1. Use a .348 Winchester FL die w/o the stem to size the neck down to the shoulder of the .375 Ruger case.
2. Use a .280 Ross FL die w/o the stem, backed off 1/16" from the shellholder and resize.
3. Resize again, as above, but with the shellholder contacting the bottom of the die.
4. Trim to 2.600 and deburr.
5. Resize again with the expander stem in the FL die and check to see if the cases chamber in your rifle.
Following this procedure I lost only one case out of the 50. I annealed the case necks and shoulders afterwards. Fired cases look wonderful and do not show that ugly bulge you get forward of the belt by using .300 H&H or .375 H&H brass.
I have tried several powders and bullet makes and weights in my rifle but have settled on the following load. 55 gr. of IMR 4350, Federal 210 primer and a Hornady 175 gr. spire point, seated to 3.500" COL. Velocity averages out to 2557fps with groups running about 1" at 65yds. My rifle has a 6X Weaver and a somewhat frosty bore but still shoots quite well. I plan to take it deer hunting this coming Fall.
I have done a similar process using a 338 win mag die with the decapping rod assembly removed to squeeze
just the neck of the 375 Ruger case down to 338. Then I run it into the 280 Ross die- once without the decapping rod assembly and then again with the decapping rod in place to properly expand the neck to .284.
Trim and camfer and done.
It has been suggested by a gunsmith I met, to try 28Nosler. Same case head dia and length as 375 Ruger. Should be a 1 pass operation- lube, resize in the 280 Ross die, trim and done.