I've been researching the .375 2 1/2-inch flanged nitro express in the No4 action, and here's what I've come up with. Initially I was all enthused about the conversion. Then I read somewhere on-line that Kynoch cartridges won't feed from a standard .303 military magazine. That was discouraging. I got to digging deeper and then found on the Mauser forum here that there were different loadings of the .375 in the old Lee Speed days, and some would work through the Lee Speed action and some wouldn't. The nominal OAL for the .375 is 3.1" The OAL of the .303 is 3.05" You can see already that the .375 won't fit in the .303 magazine. Making matters worse, Kynock is supposed to load .375 to 3.15" Back in the old days, .375 was used in modified Mannlichers, the older ones for rimmed cartridges. The rimmed 6.5mm Mannlicher has a rim and head diameter essentially the same as the .375 (and the .303) However, due to the fact the Mannlicher magazine is also too short to load a 3.1" round, .375 for the Mannlicher were loaded to 2.96 OAL. Different ammunition manufactures in the old days loaded cartridges to there own specs, not to a common spec as is done today. So, for Mannlichers, and obviously Lee Speeds, too, ammo loaded to 2.96 would feed, and the double gun ammo wouldn't. I now surmise I can proceed with the project, using handloads, and not factory Kynock rounds, and make the .375 NE feed through the action.

Since new Kynock cost $10 a shot, I've always planned on using handloads based on .405 Winchester brass anyway, which is much cheaper. (I might use more expensive Bertram brass, just to get the head stamp.) So loading to the correct length to feed through a magazine won't be a problem. I've planned the .375 rifle as a cast bullet shooter anyway. There aren't any good 270 grain cast bullet moulds available that I have found. The .375 is normally loaded with 270 grainers. So, I've figured on having a custom mould made. Doing so, I could control the shape of the bullet nose to optimize feeding from a .303 magazine. Of course there is always the option of using lighter bullets loaded to an even shorter OAL.

As mentioned above, I took my initial inspiration from here:http://www.lee-enfieldrifles.com/nitro.html I actually talked with the owner on the phone a couple of days ago and got a long BS explanation of how to make the .375 feed through the .303 magazine. He obviously isn't aware of the length issue.

I'd like to know how others feel about this. I still want to kick ideas around.

My project will progress slowly, but I will try to post more on the feeding issue as I learn more.