Home Forums Hunting & Shooting Custom Rifles & Wildcats Building up from 300Ultra...suggestions

Here is the situation I'm in,

#1 While I don't have any immediate plans, I will eventually hunt for a griz/brown bear in the some what future.

#2 I'm currently waiting for a new barrel to arrive. My original plan was to chamber it in 300ultra to replace the shot out factory barrel (chambered in 300ultra) on my M70. The new barrel is a Shilen select match #7 to be finished to 28". Because I had the dies/brass, I did not bump up to a .338 bore.

#3 Since the barrel was ordered, I've added a lightweight 300WSM to the mix.

Instead of a heavy truck/atv gun, I am thinking I would like to instead have a rebarreled rifle in .338. It will be either a .338ultra or a .338-378Wby. I want something that will properly handle a 250gr pill.

Sooo... can I properly use the M70 action (factory chambered in the ultra mag family) to be rebarreled for .338-378WBy? I'm unsure of my magazine OAL and feeding issues.

I'm just looking at options at this point

the 338-378 Wtby needs a larger bolt face than the 300 RUM.....just rebarrel to 338 RUM if you want/need a 338 bore.....no other changes will be necessary.

You might look at the 338 Edge, it's a wildcat based on necking up the 300 Ultra to 338. The guys on Long Range Hunting swear by this round and shoot the 300 SMKs with great accuracy. I would work great especially if you already have a bunch of 300 Ultra brass around. Shawn Carlock in ID was the initial designer of the cartridge.

If you want a big 33 then I'd just quit mucking around and build a 340 that will come in scoped/slung/loaded and ready to rock at no more than 8.5 lbs and go forth and fill up an ark!

Of course I honestly feel that you could and should well do a 338 instead, trust me it'll be all the gun you ever need.

Plus I'd do it so it was all up at 8 lbs and no mas.

Dober

I would at least take a look at the 340 WBY if it was me. The 338-378 WBY would require bolt face modifications. The 338 RUM is also good but the Remington brass is not the best quality from what I have seen.

+1. The dies for the .338 Edge are available from Defensive Edge (Shawn Carlock's shop) and Redding (and likely some others), or you can use any .338 Ultra dies for neck sizing and shoulder bumping. The advantage of the .338 Edge is that match 300 RUM Nosler brass is available and it has a powder capacity advantage over the 338 RUM for which only Rem brass is available.

When it comes to .338 caliber rounds I really believe the sane limit is .340 for most people. Thats just IMO.

No flies on the 340 , but in this case ,assuming the gun fed Ultra cases well , it would sure be easier to stick with what works and go with the 338 RUM .

I don't believe the M-70 is really compatable with the 338/378.......the size of the reciever ring and barrel shank may not be enough , along with the bolt face and locking lugs.....that 378/Rigby case is a big ol' jug..

I have travelled this road at one point having the .338 Winchester, .340 Weatherby and .338/378.

I kept the .340 and also have it magna ported and it is the most sane big game cartridge out there. The .338/378 belts you like a .378 Weatherby and does not get the gain over the .340 that the .340 gets over the .338.

It makes a clear case for the .340 when you try them all side by side.

>y .340 shoots 185 TSX, 250 Woodleigh and 300 grain Woodleighs into the same group. The 225 TSX is a wonderful single bullet choice for this round and you can hutning any legal game in the world with this rifle.

A point missed above is that the model 70 action and magazine length will not accommodate the .378 case so forget that route if you want to use the Mod 70 action.

JW

It might be worth checking out what Lazzeroni has to offer. I own two Warbirds and they are an awsome round.

.340WBY all the way. Perfect match up, and I HAVE a 338 wildcat called the 340 Tyrranosaur. Would still go .340WBY today on a new gun.