I loaded 174's to over 2750 in a standard 303 British in a modified P14 with a Shilen 303 barrel. There is little question in my mind that pressures had to be high yet there were no typical pressure signs. The ability of rimmed cases to be loaded to high pressures seems to be a common characteristic. I see the same thing in 30/40 Krag when chambered in a strong actioned rifle.
The truth is this; two cartridges of the same capacity will produce the same velocity at the same pressure if evrything else is equal. The 303 Epps has slightly less capacity than the standard 30/06 so a load which produces max pressures in a 30/06 will produce slightly higher pressure in a 303 Epps. In other words, the 303 Epps will require slightly less powder to achieve the same pressure levels than will a 30/06. Velocities will be similar.
The capacity of the 303 Epps is about identical to that of the 7.5x55 Swiss or the 7.62x 54 R.
My own 303 Epps is built on a Ruger No.1 and is actually a 30-303 since I chambered it in a 30 caliber barrel (I reduced the throat diameter to .3085 and used a 2998 pilot for the Douglas barrel). I have yet to chronograph any loads but I am expecting to easily obtain 2800 with 165's and this will be sufficient for my purpose. I had originally intende to chamber this to 30/40 Krag but ended up with a set of Epps dies and already had the reamer so I went with the Epps. I always wanted one anyway. Leeper

I love Leepers stuff. He has done some really cool things. That is all

Epps sporting goods in Ontario will still do the ream job to .303 EPPS
I just called them

Bringing this back from the dead. Who in Alberta has the 303 eps reamers and is willing to do the work.

I'm wondering about this as well. I have a P-14 Enfield and possibly a Ross M10 that I was thinking about turning into 303 Epps. I would want to make them with .308 barrels though to take advantage of a wider selection of bullets.

With the 308 barrel would one require custom dies?

It would definitely require a custom reamer and a new barrel. I would just get a standard 303 reamer with a 30-06 neck and lead combined together.

As for dies, you could get away with a 303 body die and a 308 or 30-06 neck die with bushings to take care of the slightly smaller diameter. Or go custom if you really want to.

It's been a project on my mind for quite a while, especially for the Ross.