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Discussion in 'Gunsmithing' started by Moman, Jan 13, 2012.
Can the bolt face of a Mark V in 300 Wtby be opened up into the .585 range?
Yes. very easy and the extractor for a 30 378 can be used with little if any modifications.( you
can order the extractor from Weatherby).
J E CUSTOM
I would order a spare while you are at it...
Alright, thanks guys. I found a japanese Mark V in that caliber and it seemed like a decent price. Thought I might pick it up for a future build.
The extractors are pretty weak, this is the only down fall of this action as far as I am concerned. But they have only broken for me when I was doing load development and got a little pressure sign.
Yeah, something in that range. I can get this action for quite a bit less than going custom so thought I would give it a try.
Old thread, but someone should chime in.
The 30-378 or 378 Weatherby has a Lapua-Norma boltface correct. Would that mean it is stronger than buying a 300 Weatherby and opening it up?
That was my impression anyway. Who might know that answer?
Yes, it can be opened up. No, the 378 is not stronger.
I stopped by Weatherby specifically to broach this subject. I live near there.
Yes for $300+ more than a 300wby or 340wby Mark V you can get a 378 Mark V but they are the same except for the machining on the bolt face and the extractor.
Never hurts to get an extra of something like an extractor if you are going to push things very hard.
I just bought a 30-378 stainless, one of the original Mark V's so I just don't have to have the boltface opened up. I paid 805, which I think is a pretty good price. It has a composite stock and only about 50 rounds down the tube. I'm going to convert to 300 Norma though. Although I'm tempted to play with the 30-378 a little. If I have it re chambered, can the barrel be taken off and put back on if I want to go back?
Thanks for telling me about the boltface. I'll keep that in mind.
Most barrels can be set back about one thread without weakening it, but I don't recommend any
more than that for the big magnums.
Some cartridges require to much set back to re use a factory barrel with the factory contour (Custom barrels normally have more shank and removal of the entire shank is possible).
The 30/378 is a great round and all it would cost you to find out how well it shoots is a box of
ammo. I would recommend the 180s because recoil will be brisk with the factory barrel and
rifles weight. (Probably why the guy sold it).
J E CUSTOM
The barrel on a Weatherby goes on and off just like a lug nut on a truck. No harder than anything else.
I believe most 30-378's built in the last 15 years came with a muzzle brake that does a pretty good job. I have no trouble with the larger 338-378 even with 300 grain bullets.
The Weatherby barrel has a relief cut at the end of the threads up against the barrel. If you try to set it back it won't have much threads left.
I agree with JE, just run the 30-378 like it is but I would use heavier bullets 200 grain and up.
Thanks, I've decided to get a JP break for it and give it a run. If I don't like the round I can always sell the dies and the barrel as it's barely broken in right now. The 300 Norma can be done anytime in the future. Thanks all for chiming in.