Free bore in weatherby rifles

Big grizz

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I own a 378 Weatherby Mag in a Weatherby MKV deluxe rifle, I am trying to work up an accurate load using Barnes 270gr TSX bullets. I measured overal lenth with a sinclair overal length tool and if I seat bullets so they will just fit into the magazine, my rifle has 0.585" freebore. This is over 1/2 inch!!!
Is this excessive or normal for a factory weatherby rifle barrel?
I have measured this with several different bullets and they all come up with simular results. Thanks for any info..
 
I've seen lots with 3/8 inch freebore and this is what I suspect yours is.

Some of the 378 factory loads were super hot so you don't want to mess with the freebore.

They still shoot very well.
Are you having accuracy issues?
 
Have not shot any TSX's through it yet. Maybe in a couple of days. Have owned this rifle for about 15 years and tried several other bullets and could not get them to shoot. BUT, I had a Shepherd scope on it and it may have been the problem, I don't think it can handle the recoil. Just mounted a Swarovski Z6 2.5 to 15 power with Ballistic turret. With the shepherd scope, it would shoot about 12" groups and be all over the place. I never used the rifle because it would not shoot. Had it accurized by a very good gunsmith who recrowned the barrel, bedded the action and free floated the barrel and a trigger job, all to no avail. He said the rifle should shoot and also suggested changing the optics. I sent the scope back to shepherd twice and they sent it back both times saying nothing was wrong. I explained to them that it was on a 378 weatherby and they said they can take the recoil, but after every shot I have to reset the paralax adjustment for the two reticals in the scope, and they are trying to tell me nothing is moving from the recoil, B.S. I will try again with new scope as I was lucky enough to draw a Grizzly bear tag for this spring in BC, and wanted to use this rifle for the task.
Just went on Weatheby's web site and seen in the Frequently asked Questions link, there is one on free bore on thier rifles. shows free bore for the 378 to be 0.756" I had no idea there would be this much. this computes with my measurements as I was going off of maximum magizine length as a starting point, not recomended COAL.
Thanks for listening and appreciate any advice.
 
Yes, rifle is bedded by a very competant gunsmith that worked for the RCMP Armoury in Regina Sask.
I am going to load up a few test loads today and should be able to try them in a couple of days. Hopefully the new scope is going to solve my issues. If not I will be picking everyones ears again on what to try next. Rifle will be shot in a lead sled rest and is rock solid to eliminate any human error. I really think it was that Shepherd scope, but wont know until I try it with the Swarovski.

When I shot it with the Shepherd, it would sometimes shoot 2 or 3 shots in a nice group and then the next shot would be 10" away and the next shot would be 7 or 8 " from that one, there was just no ryme or reason to where the bullets would land.
 
Let me know how you make out....Shepherds aren't known for high recoil integrity.
 
The Led Sled can be tough on scopes too. Have you tried it over sandbags?
I would try some Hornady 270gr SP as a test. They always seem to shoot well.
What powder are you using?
 
Will let you know how I make out with new scope. Last tests were done from bags, not the lead sled, just bought the lead sled and have not used it yet. Powder being used is H4831sc, and I have tried the 270gr Hornady SP. I am going to try several other powders, including RL22. Magpro, Magnum, and IMR7828ssc.
 
Here are some loads for the 270gr TSX from Barnes (disregard if you have the manual already)

RL 19


start 102.0 max 110.0

H4831SC

start 102.5 max 110.5

MagPro

start 112.0 max 120.0

RL 22

start 104.5 max 112.5

IMR 7828SSC

start 104.5 max 112.5

Magnum

start 114.0 max 122.0

Keep us posted on how things go.
 
Hey guys, made it to the range today, tried out my 378 with the new scope and some new loads. Rifle accuracy problems - GONE - with Swarovski scope, that D!#mn Shepherd scope was the problem all along. I tried 4 powders, RL19, RL22, IMR7828ssc, and H4831sc with the 270gr Barnes TSX. Got the most velocity with 110.5gr's of RL19 at 3142fps with an extreme spread of 21fps in 5 shots, accuacy was OK, may have been better if I had let the barrel cool, when I fired this string my barrel was extremely hot, burning my hand hot!
Best group was with 113gr's of RL22 at 3102fps and an extreme spread of 27fps. This group shot with cold barrel, ( I took a break and switched rifles ) measured 1/2" for 3 shots. All other loads were shot with hot barrel and accuaracy was average. I tried 113gr's IMR7828ssc wich yielded 3051fps. and 111.5gr's of H4831sc yielded 3076fps. All loads gave extreme spreads of less than 30fps and absolutely no pressure signs. Primers still have round edges and bolt lift was one finger. I know that the factory ammo I have shot is much hotter than these loads, could probably get 3200fps with no problems.
Thanks to those who responded with suggestions and will let you know of further testing
 
Good to hear!
Frankly I think the Shepard scopes are crap.
The 378 eats weak scopes!

Weatherby builds an accuracy rifle...Glad to see yours is no exception!
 
Yes, I definately will not buy another shepherd scope, they may work fine on varmint rifles, but are obviously not designed for big magnums.

Whats your thoughts on getting 3200 fps?

I had a box of Weatherby factory ammo loaded with hornady 270gr soft points, and they went over my chrono at an average of 3250fps.

the north american reloading manuals say there is no standard pressure level set for the weaterby cartridges, so they set their limits to 60000 psi, but I think that Norma loads the Weatherby ammo a lot higher than this.
any thoughts? As I said at the velocities shown above, cases show absolutely no pressure signs.

Thanks.
 
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3200 can be done, but its hard on the brass.
The big Weatherby brass could and should be better.

Honestly?
I would stick with the most accurate load...Another few FPS makes no real difference.
 
The Wby pressure levels are the same as they are for any other magnum, that's North American industry standard. Norma certainly used to load hotter then that, I don't know if they do anymore. As to the freebore, early Wby's had 3/4", then 1/2", then 3/8", as time went on. I have an early Wby 375 (among others) that has the 3/4" freebore, and it's a fussy eater too. - dan
 
The standard Wby magnum brass is fine, but the super magnums stuff is a bit soft for my tastes. I suspect this has to do with the large bolt face area.


FWIW

I have a pair of 375Wby rifles. My Sako shoots just over MOA with any load or bullet and makes bugholes with selected powder charges. It has shot every bullet on the Canadian market into a very respectable group....Great gun!
My Brno shoot 1.25 MOA with good loads and 1.5-1.75 with crappy ones. It shoots exactly the sames as when it was a 375H&H.
Mine are not fussy at all.
 
The standard Wby magnum brass is fine, but the super magnums stuff is a bit soft for my tastes. I suspect this has to do with the large bolt face area.


FWIW

I have a pair of 375Wby rifles. My Sako shoots just over MOA with any load or bullet and makes bugholes with selected powder charges. It has shot every bullet on the Canadian market into a very respectable group....Great gun!
My Brno shoot 1.25 MOA with good loads and 1.5-1.75 with crappy ones. It shoots exactly the sames as when it was a 375H&H.
Mine are not fussy at all.

I also have a Brno 602 in 375 Wby. What loads do you use?
Mine has a Gaillard barrel. I have some 260 and 300 Accubonds to try out.
 
Are you guys talking about the improved 375H&H round that weaterby chambered briefly as the 375 Weatherby, or the actual 378 Weatherby Magnum?
There is a big difference between the two.
 
Dan Belisle.
According to Weatherby's web site, mine was built in Japan between 1972 and 1994 as it has the "H" prefix on the serial # and also has the 0.756" Freebore.
What kind of loads have you had the most success with?
 
Are you guys talking about the improved 375H&H round that weaterby chambered briefly as the 375 Weatherby, or the actual 378 Weatherby Magnum?
There is a big difference between the two.

Yes, we are talking about the 375Wby, not the 378Wby. It was reintroduced and is still being loaded by Weatherby.
 
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