Rechambering a 300 Weatherby to a 378 weatherby

The Accurate Reloading Forums

This topic can be found at:
https://forums.accuratereloading.com/eve/forums/a/tpc/f/9411043/m/2951097031

12 April 2010, 15:57

rutten

Rechambering a 300 Weatherby to a 378 weatherby

Recently received a Mark V 300 Weatherby action from a friend. Was wondering if it is possible to use this action to build a 378 Weatherby. Was wondering if opening up the bolt face would be do-able and also if the 300 magazine would accommodate a 378 case or would there have to be modifications done. Guess I am just wondering if it is possible.

12 April 2010, 16:57

jeffeosso

short answer is no.
the 378 is larger in diameter, and longer, won't fit mag or bolt. requires a rebarrel not rechamber, btw

opinions vary band of bubbas and STC hunting Club

Information on Ammoguide about
the416AR, 458AR, 470AR, 500AR
What is an AR round? Case Drawings 416-458-470AR and 500AR.
476AR,
http://www.weaponsmith.com

12 April 2010, 20:08

AfricanHunter

quote:
Originally posted by rutten:
Recently received a Mark V 300 Weatherby action from a friend. Was wondering if it is possible to use this action to build a 378 Weatherby. Was wondering if opening up the bolt face would be do-able and also if the 300 magazine would accommodate a 378 case or would there have to be modifications done. Guess I am just wondering if it is possible.

Design of magazine box and follower are different, but I would expect you could get correct ones from Weatherby. I would think any 'smith worth the name could handle the bolt face alteration.

13 April 2010, 06:49

PoppaW

Weatherby will sell you the box and follower. Put a new barrel on and open the bolt face. Oh and a new extractor. Fairly easy to do.