One of the first issues I've encountered is the chamber was designed for thinner rims. The modern .303 brass I have is by Winchester, and it looks like I will have to do something about thinning the rims, to get them to chamber. Any suggestions on sources for "thinner rim" .303 brass?
The "bad" news is that a few years ago a discussion on an Enfield forum identified a batch of Winchester ammo as already having thinner rims than other modern brands and was currently thinner than the published specification (
https://enfield-rifles.com/303-rim-thickness_topic10315.html). So that doesn't look promising.
Since it's an older rifle, you may have to go onto a place like GunBroker and try to find some older ammo (possibly mil spec) to see if you can find something suitable. The problem with this option is the random hit-or-miss nature of blindly trying potentially expensive options. I have four types of .303 British ammo: 150gr Hornady, 150gr Federal, 150gr S&B and 174gr Graf & Sons (which was loaded by Hornady but uses PPU brass). If you send me a PM with your address, I can send you a sample of each for testing if that would be helpful.
Otherwise, to my way of thinking, I would probably look at getting a gunsmith to determine if milling the chamber to fit modern rounds was an option. This of course might be an unacceptable option based on cost or an aversion to modifying a historical rifle. That is obviously a personal judgement call if it's even doable at all. Another option might be to send a PM to
Steve Redgwell and ask him. He runs
https://303british.com/ and comments on this caliber in other posts here. Maybe he has some useful insight.
I have a nostalgic affinity for the .303 British ever since I shot my first deer with one. I currently own two falling blocks in this caliber. Here's another Holland & Holland that sold for $2,588 a few years ago. That's a pretty rifle!
Last year I was looking around for some scope mounting blocks for an 1885 I was mounting a Malcolm scope onto at Steve Earle's website (
https://www.steveearleproducts.com/index.htm) when I saw that he was producing a similar Fraser action. I already have too many projects I'm juggling but I couldn't help think it would be cool to build a custom rifle in a classic caliber if I had several thousand dollars laying around that I didn't know what to do with.
The fact that the action came in a left-handed version made it even more intriguing (and expensive!) to me.