ELR 338-378 Weatherby

[Timber338]

So one of my hunting buddies owns a semi-custom 338-378 around a Weatherby Mark V action, but it only has a 26" pac-nor barrel on it. He has finally gotten around to realizing he wants a true ELR elk/bear rifle and is looking to getting a really long heavy contour barrel... something on the order of 34-35 inches long plus a brake. And shooting the Berger 300 grain Elite Hunter.

I wanted to see if anybody out there who has a rifle like this could pass along any advice? I've never loaded for the 338-378 so what are the top powder choices? My guess is that H-1000 would work, maybe RL-33? Are there other powders that are better?

Are there any pitfalls to an ELR build around the 338-378?

Dan Lilja wrote a great article where he started with a 46" barrel and collected velocity data while he continued to cut the barrel down in 2" increments.

Lilja Precision Rifle Barrels - Articles: Barrel Lenghts and Velocities in the 338/378 Weatherby Magnum

Thanks in advance

 

[dkhunt14]

It takes a really long stock to balance out that long of barrel. It also takes a stiff action to hang the barrel on. It also has to be a Heavy contour to handle the length and heat. We shoot 36 inch 1.450 diameter barrels but have them in a barrel block to hold the barrel and action and stiffen them up. My buddy has a 338-378 in this configuration and has shot H50BMG and Re33 really well with the 300 Berger. It is not the speed but accuracy that kills. If you go to the Longrange Hunting and Shooting forum and look at the thread Pictures of my hunting rig you will see Pictures of my gun. Matt

 

[Timber338]

It takes a really long stock to balance out that long of barrel. It also takes a stiff action to hang the barrel on. It also has to be a Heavy contour to handle the length and heat. We shoot 36 inch 1.450 diameter barrels but have them in a barrel block to hold the barrel and action and stiffen them up. My buddy has a 338-378 in this configuration and has shot H50BMG and Re33 really well with the 300 Berger. It is not the speed but accuracy that kills. If you go to the Longrange Hunting and Shooting forum and look at the thread Pictures of my hunting rig you will see Pictures of my gun. Matt

Thanks Matt. That's an impressive rifle you've got! All great info in the threads you've started about your build. Overall I think it's more rifle than my buddy wants to tackle... probably going to scale his barrel length back to a max of 30".

I'm trying to talk him in to selling his rifle as-is, and going with a proven setup... something like a Canyon Rifle. He wants to save some money, but I'm worried that he won't get the accuracy from his Mark V action.

 

[idaho elk hunter]

I have had many of these IMo t is the finest over the counter cartridge for Long Range Hunting. 338s are a hammer. This is a sledgehammer. The longer barrel is going to support 20 to 25 fps per inch. Not as much as one would think. After every conceivable combination with every bullet, The hardest hitting combination is a 250 gr bullet with a load of RL 25. you should end up around 11gr or there abouts. 3250 fps. The 300 gr bullets are great but they will notbe as flat shooting or have as much retained energy at 1000 yds.

 

[dkhunt14]

I agree the 250 is better to 1000 but a lot of shooting we do is at 1500 plus and the 300 is better. Also I like the bullet to pass through no matter what it runs into. I also believe hanging a 36 inch barrel on a Weatherby action is not what I would do. If you use a 36 inch barrel it needs to be heavy or the heat will make it walk all over. When we use 36 inch barrels we use 1.450 diameter and glue them in a barrel block. There is nothing wrong with the choice of 338-378. I just like my Lapua Imp better because of the Lapua brass. I can get 3100 plus with a 300 so they are about equal. Matt

 

[Timber338]

I agree the 250 is better to 1000 but a lot of shooting we do is at 1500 plus and the 300 is better. Also I like the bullet to pass through no matter what it runs into. I also believe hanging a 36 inch barrel on a Weatherby action is not what I would do. If you use a 36 inch barrel it needs to be heavy or the heat will make it walk all over. When we use 36 inch barrels we use 1.450 diameter and glue them in a barrel block. There is nothing wrong with the choice of 338-378. I just like my Lapua Imp better because of the Lapua brass. I can get 3100 plus with a 300 so they are about equal. Matt

It didn't take long reading the thread on your rifle to realize that the idea of a 35" barrel on a Weatherby action was a bad idea. You provided exactly the information I was looking for, passed it along to my buddy, and he is re-thinking the whole thing.

Overall I think he should start from scratch with a custom action, but $ for a full custom build is definitely a valid reason to stick with the Mark V.

Thanks again for your advice on this. Perfect example of why this forum is so valuable.

 

[sp6x6]

If your patient youll see about everything for sale on here.Ive seen canyon rifles ,338 ax,338 am,375 cheytac,375 am,etc.Dont think Ive seen a used LRMK yet

 

[Outlaw6.0]

I don't believe there is anything wrong with you buddies MK5 action. It's big & it's strong enough to build a great custom rifle from. The down side is, aftermarket support for you WBY is going to be limited compared to others.

I agree with others that a 34-35" barrel isn't a great idea, 30" will get you all you need while keeping the weight down.

The up side is, you buddy is saving ~$1500 on his build by already having a usable action in hand.

Pro's vs Con's... How much does he want to spend?


t