Okay - excluding possible feeding problems, what's the largest diameter bullet/cartridge (I handload and know what I'm talking about - just not that darn articulate right now...) that I can stuff in a rifle made on a 14 or 17 (still not sure which it is) Enfield?

On that case head size? A .475 Ackley/.470 Capstick. Nearly cylindrical.

Yup. On the .532 case head, a 470 capstick is it. And a darn nice caliber too.

If you are going to the expense of converting a 14 ore 17 to big bore use, then there is no reason not to consider opening up the bolt face, as it is a triveal expense compared to the whole cost of the project. With that in consideration, you can use the 460 Weatherby case for a 50 caliber, the 500 Jeffrey, 505 Gibbs and 585 Nyati. Oh yeah, almost forgots Robb's 600 on the belted 577 NE case blown out for the .620 pills.

If I were going to use a 1917 Enfield, I would build something serious on it. You can easily open the boltface to .590 ( 470 MBOGO, 500 A2) or .640 ( 505 Gibbs, 585 NYATI or .600 OK) with that one or go to .688 and build a T-Rex. You will need a P-14 bolt for these conversions, but that's the least of your problems. If you stick to .532, then I agree a 470 Capstick is about it. Just be aware this is not the easiest action on which to build a big bore. Make sure you have a gunsmith who knows what he's doing.-Rob