Re-chambering to 303 Win Mag wild cat

[kombi1976]

I've been thinking over a project over the last couple of days and wondering whether it'd be effective long term.
Years back a number of Canadians rechambered their P14 and M17 rifles to 300 Win Mag(because of their superior action strength) but stayed with the 303 cal barrel, loading .312 cal bullets instead of 308 cal to retain accuracy.
Since the head size for 303 Brit rim is the same as magnum rim sizes there was no need to play with the bolt face(correct me if I'm wrong here).
But something concerned me about such a conversion.
The barrel twist used in Enfield rifles is 1 in 12"(again I may be wrong, please set me straight if I am).
But what is the most common barrel twist on rifles chambered for 300 WM?
In other words, would the original barrel twist properly stabilise the bullet at the speeds a 300 WM powder column will push it at?
There are companies that produce suitable bullets to cope with these velocities, Woodleigh of Australia and GS of Sth Africa to name a couple, but is it capable to produce an accurate long range rifle from such a project?

[gunnut69]

Normal twist is 1 in 10 for the 300WinMag and most 30 caliber rounds.  Barrels are made in 1 in 12 but would likely not handle the heaviest bullets well, and of course those are the bullets that perform the best at long ranges.  It would likely work OK with lighter weights but fail to properly stabilize the longer, heavier bullets the big magnum cases favor..  A barrel is not all that expensive in the grand scheme of things...

[Rick Teal]

I have a "303 Canadian Epps Belted Magnum".  This was a P14 chambered to a .308 Norma but shooting a .311 bullet.  Factory specs on the .308 Norma place it slightly ahead of the WinMag, but brass is relatively hard to find.

My father had this gun made back in the '60's, and found it to be very accurate with 180 grain bullets.  He (nor I) have tried heavier bullets to date, however, I've just begun swaging my own .312 bullets, so I expect to be testing heavier loads soon.  I don't know the twist rate of the P14, however, I would expect it to be sufficient to stabilize a 215 grain bullet, which was still a common military loading when the gun was designed.