Trying to make decisions Building a 338-378 Weatherby

N

NorthernWeatherby

Member
Joined
Jun 2, 2009
Messages
24
Location
Prince George, British Columbia, Canada
I am building a 338-378 Weatherby Magnum. I am starting with a Nesika round action, I have no experience with Nesika, but have chosen them for a few reasons(if anyone has a thought on this let me know.) I am going to go with a 28 -30" fluted barrel with a 1 in 10 gain twist. I currently have a .300WBY Mag. with a 1 in 10 gain twist with a 28" fluted barrel 1.25" to .8" taper and it shoots very well, I have not pushed it past 500m. I am building the .338 to cover 500m to 1200m.

Can anyone give me advice on these choices. I have been shooting for the better part of 20 years and am accustomed to recoil, the rifle will be heavy and should not be to bad to shoot in the prone position.

NorthernWeatherby
Custom .300 Weatherby Magnum
gun)
 
Welcome to the site.

What bullet are you planning on shooting, Sierra MatchKing 300gr?

Should work well for that.

AJ
 
Nesika was sold a few years ago and their quality control might not be what it once was. You might consider a different action.
 
NorthernWeatherby said:
I am building a 338-378 Weatherby Magnum. I am starting with a Nesika round action, I have no experience with Nesika, but have chosen them for a few reasons(if anyone has a thought on this let me know.) I am going to go with a 28 -30" fluted barrel with a 1 in 10 gain twist. I currently have a .300WBY Mag. with a 1 in 10 gain twist with a 28" fluted barrel 1.25" to .8" taper and it shoots very well, I have not pushed it past 500m. I am building the .338 to cover 500m to 1200m.

Can anyone give me advice on these choices. I have been shooting for the better part of 20 years and am accustomed to recoil, the rifle will be heavy and should not be to bad to shoot in the prone position.

NorthernWeatherby
Custom .300 Weatherby Magnum
gun)
Click to expand...

The 338/378 is an awesome round and should do everything you want it to.

I don't know much about the Nesika action but it should be OK.

As to the barrel, 28'' to 30'' will produce good ballistics. I would not flute the barrel
because you will need the weight unless you put a brake on it.

My best piece of advice is to have you or your smith hold the head space to less than
.001 (I set mine .0005 to .0001). solving the free bore issue.

And you should neck size only to improve brass life, even then don't expect more than
3 or 4 firings.

I would look at the 250gr accubond for hunting and the 300gr SMK for targets beyond
1500 yards.

Just my 2 cents.

J E CUSTOM
 
Last edited:
My .300WBY Mag. is based on a Japanese Mark V action, the only reason I am thinking of not going with a Mark V is the one I have now is starting to lose its smoothness. Becoming what feels to me as a little loose. I was thinking of something with tighter tolerances. Due to availabilty it would be an easier action to go with for sure. Do you think that a tighter action is going to make that big of a difference? Worth the extra cost? If this rifle shoots well it is likely that I will not build another one. I still have the same Model 60 Cooey I had when I was 10 years old, it shoots like nothing else and I will never replace it for that reason.
 
I still hunt with my original 338-378 that I built on a mk 5 action in 1979. 28" hart barrel that still shoots like a dream making half mile shots on big game fairly trivial. This particular rifle was built for the 250 gameking which had just came out with the highest BC of any hunting bullet ever produced up until that time. It was for sure a new innovation in hunting for that time pushing the 250 nearly 3400 fps. Now I am pushing the 225 AB at over 3500 fps with a .550 BC. The big 6 point bull elk I shot last year with it just dropped in his tracks at 814 yards.

You will need a muzzle brake on the rifle to shoot it accurately. 28" barrel is long enough since you gain very little velocity with barrel length in the big 338's. I currently own seven 338-378's along with numerous other big 338's. If most of your hunting doesn't exceed a half mile the 225 AB will have a much flatter trajectory and kill anything you encounter inside that range unless T-Rex is reincarnated. If your hunting goes out to a 1000 yards and beyond shoot the 300 matchking with Retumbo or H-870 and you can get it over 3000 fps in the 28" barrel. I have seen them shoot clear through an elk at over a thousand yards out of a 338-378.

I hunt with all the popular big 338's off the wby, lapua and ultramag cases. There is not a whole lot of difference in any of them but the big 378 case and the 416 improved case gets a little more velocity to take away a few clicks in elevation and wind since time of flight is a little quicker.
 
Well it looks like I might have to go back and re-think things for a bit........Hopefully not too long. I would like to be shooting this rifle some time in 2010......Thanks everyone for your 2 cents.....any more comments would be appreciated......while I go back and weigh things up again.lightbulb
 
NorthernWeatherby said:
My .300WBY Mag. is based on a Japanese Mark V action, the only reason I am thinking of not going with a Mark V is the one I have now is starting to lose its smoothness. Becoming what feels to me as a little loose. I was thinking of something with tighter tolerances. Due to availabilty it would be an easier action to go with for sure. Do you think that a tighter action is going to make that big of a difference? Worth the extra cost? If this rifle shoots well it is likely that I will not build another one. I still have the same Model 60 Cooey I had when I was 10 years old, it shoots like nothing else and I will never replace it for that reason.
Click to expand...

You might check into the TFE coating for bolts. If you tell them not to remove any bolt material
before coating It will tighten it up a little and boy is it slick.

If you decide to use the 300 Weatherby action all it would cost is the price of the coating
and for the smith to open the bolt face.(Very simple on a Weatherby).

Have the bolt face opened before coating the bolt to prevent damage from the Lathe.

J E CUSTOM
 
Long Time Long Ranger said:
I still hunt with my original 338-378 that I built on a mk 5 action in 1979. 28" hart barrel that still shoots like a dream making half mile shots on big game fairly trivial. This particular rifle was built for the 250 gameking which had just came out with the highest BC of any hunting bullet ever produced up until that time. It was for sure a new innovation in hunting for that time pushing the 250 nearly 3400 fps. Now I am pushing the 225 AB at over 3500 fps with a .550 BC. The big 6 point bull elk I shot last year with it just dropped in his tracks at 814 yards.

You will need a muzzle brake on the rifle to shoot it accurately. 28" barrel is long enough since you gain very little velocity with barrel length in the big 338's. I currently own seven 338-378's along with numerous other big 338's. If most of your hunting doesn't exceed a half mile the 225 AB will have a much flatter trajectory and kill anything you encounter inside that range unless T-Rex is reincarnated. If your hunting goes out to a 1000 yards and beyond shoot the 300 matchking with Retumbo or H-870 and you can get it over 3000 fps in the 28" barrel. I have seen them shoot clear through an elk at over a thousand yards out of a 338-378.

I hunt with all the popular big 338's off the wby, lapua and ultramag cases. There is not a whole lot of difference in any of them but the big 378 case and the 416 improved case gets a little more velocity to take away a few clicks in elevation and wind since time of flight is a little quicker.
Click to expand...






What do you think of Gain-twist, and fluting?
 
NorthernWeatherby said:
I might seem a little behind.......What is TFE coating for bolts? Is this something that can be done by a gunsmith? Or do I have to send the bolt away for it.......I like my .300 mag very much and it would be nice to tighten it up a little......:rolleyes:
Click to expand...

Sorry it took so long to reply but my computer crashed.

TFE is nothing more than a Teflon based coating that is applied for protection of un blued
parts.

When applied to a rifle bolt it makes it very slick and adds about 1 mill to the diameter
of the bolt.

It appears to be very tough and holds up well under use.

If you post a thread asking about coatings ,you will/should get lots of replies about what
kind of coating works best and where to have it done.

I have lost touch with this process but I know it is still being done.

J E CUSTOM
 
Thanks everybody. I have ordered two heavy .338 gain twist barrels from Ron Smith, both at 30" . And have found myself a good used .378 Mark V action. Old timer I know had one in the back of his safe......go figure. So now on to headspacing issues.......gun)Any Advice on stocks??? I hope to be shooting soon.......but for now just out with the .300 Weatherby Mag. Getting ready for a Bighorn hunt.....wish me luck.

Northern Weatherby
.300 WBY Mag. Custom
.338-378 WBY Mag. in the works, but progressing nicely.
 
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