I am going to build a custom #1 in 303 British. I understand that bores vary from .310-.312. Which is the best for modern ammo and jacketed bullets?

Thanks!

.311

.310

this way you can shoot all "30" cal bullets with a minimum of undersize or oversize

I heard Ruger is making a special run of #1's in .303.

.311 ,, which perfectly shoots .311 303 bullets

Or, if your handloading assuming you live in the states, .308! I would go with .310.

The bore dia. is roughly .303". Groove dia. as much as .313". .310 to .312 dia. bullets work just fine or have so far. roger.

I think that first you need to determine which bullet(s) you intend to use.

The outside diameter of those bullets should tell you what groove diameter you want your barrel. What you probably don't want is anything over bullet diameter, so that no gas can scoot past the bullet in the bore even before it "bumps up" to fill the grooves.

Such "blow-by" will be caused by the physics of the situation to greatly accelerate the gas, thus increasing the likelihood of gas-cutting both bullets and barrel.

Ordinarily I wouldn't get too hung up on it, but with a "Custom" rifle, the profile of the barrel and its cavity in the stock forend will also likely be "one-off". Replacing such bqrrels with custom profiles can be quite expensive and if you don't get the same profile when you must eventually replace the barrel, the stock work required may not be cheap either.

So, I'd want as little gas-cutting in my barrel as possible.Besides, a good bullet/barrel match is likely to make for easier good accuracy.

the Brits measured tthe bore on the .303 from the lands,NOT the grooves of the barrel-so you need bullets of .311 dia...best wishes from Limeyland....

Save some money and use it to go hunting with.

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