Reloading for Canadian 303 Ross Rifle

[ireload2]

Ray,
Sorry I am late to this party. Looks like your chamber is reamed even larger than any fired .303 case I have ever seen. I buy lots of once fired brass when I can find them.
Have you ever made a chamber cast of your chamber?
As far as suggestions go:

1. The 7.65 Mauser can also be use as a neck sizer if you are careful not to set the shoulder back.
2. If your chamber is much larger at the head than a maximum Lee-Enfield chamber you could possible reform other brass if you do not shoot a lot.
Do you have any idea how you headspace is set up? It appears the Canadian method for the #4 eventually was the shortest bolt head without going over .074. I ask about the headspace because Hornady .405 Win brass (pricey) has .457 to .458 heads but the rim is a little thicker at .068 to .070. The rim is also a little larger in diameter.
.444 Marlin can also be reformed but it runs a little large than most .303 chambers so it required the head be swaged or reduced slightly.

[tiriaq]

The phot of the fired case shows pretty much what you would expect from a Ross with the altered chamber. The rifle no doubt has E, or LC stamped on the top breech of the barrel.
I would suggest that if you want to reload cases fired in this rifle that you try a Lee collet type neck sizing die. Or a conventional neck sizing die that contacts only the neck, but no part of the body.

[Alfred]

Looks like it was reamed for another cartridge altogether. Could be they adapted the reamers used for some other chambering.
Should make headspacing on the shoulder easier with that much surface area.

[tiriaq]

The chambers were deliberately reamed oversize in a misguided attempt to eliminate jamming problems. Some rifles were altered in a workshop in England. New production rifles were made with the enlarged chambers after the introduction date. There are different patterns of enlarged chamber.
FWIW, chamber drawings for the SMLE were revised in 1915 because of the same ammunition problems that affected the Ross.
Cases fireformed in a specific rifle could be treated as if headspaced on the shoulder, but this can be done with many calibres.

[green]

MkI and early MkII Rosses were made with a .299" bore and a .309" groove dia. even though they were .303" cal. It is advisable to check the bore size on these arms.

[tiriaq]

Yes. Many do. My II** (1912, I think) commercial target rifle has a .303 barrel. With Rosses it is best not to make assumptions. I do not think any Mk. III rifles were made with the tight bore.
Some Mk. II rifles had their chambers reamed, as well.