300 weatherby again

[Kenneth66]

Bought a Hornady OAL gauge and got the modified case for the 300 weatherby along with a couple others . Decided to gauge the OAL on a couple rifles , when I did the weatherby there is a tremendous difference in OAL of Weatherby factory ammo and the ones I gauged with the modified case . Right at a 1/2" , that seems pretty extreme to me .
The Berger 210 VLD hunting bullet and 180 gr Nosler E-Tip didn't set in the case much and the 180 gr SGK didn't even seat deep enough to stay in the case .
Do I have a seriously eroded throat ?
Thanks , Kenneth

 

[KMart]

I think you are dealing with a typical Weatherby caliber chamber. They all seem to have veeeeery long throats.

 

[nicholst55]

That's the 'magic' Weatherby freebore you're seeing.

 

[MagnumManiac]

Weatherby’s have freebore built into the chamber.
Traditionally, older reamers ran .375”-.500” freebore, however this has changed today.
Of the chambers that run freebore, the 240 Weatherby DOES NOT, the freebore is from .250”-.375”.
In the 50’s, one of the chamberings had .750” freebore, it escapes me which one.
My own 375 Weatherby has .500” of freebore, that is what I wanted so I could comfortably get 2850fps with 300gr Woodleighs, these bullets WILL NOT sit in the case mouth if I put one in the barrel then close the bolt on an empty case.

Freebore reduces pressure (start pressure) allowing more powder usage and higher velocities.

Cheers.

 

[Kenneth66]

Ok , that's a relief to know . But a little confusing , as I have always been taught the less bullet jump , the better .
So , I guess I just start at the longest OAL that will work in the magazine and look for a sweet spot ?
Edited for an after thought , would it be reasonable to put less concern in the OAL and try tune with powder and powder wieght ?
Thanks , Kenneth

 

[wboggs]

Ok , that's a relief to know . But a little confusing , as I have always been taught the less bullet jump , the better .
So , I guess I just start at the longest OAL that will work in the magazine and look for a sweet spot ?
Edited for an after thought , would it be reasonable to put less concern in the OAL and try tune with powder and powder wieght ?
Thanks , Kenneth

I used to get pretty good accuracy from my 1960 mark 5 with the long freebore by loading to overall factory length. You will have to experiment with loads. You need more powder with the huge freebore.
Bill

 

[6MMsteve]

Roy designed the chamber or barrel with all that free bore to get the high velocity, that's why he was called the High Priest of High Velocity, Mr Bullet Jumper, I wonder if he has met F Guffey Mr Shoulder Bump

 

[Bart B.]

SAAMI chamber drawing shows 300 Wby Mag freebore at .3084 inch. Then a 1 degree 2 minute leade angle.

300 Win Mag spec is zero freebore then a 1 degree 26 minute 37 second leade angle.

 

[Zero333]

If you're going to use these loads from a magazine, then yes, load them at least 0.050" shorter than the magazine will allow and try to find the best powder charge weight.,

Once you find the best charge weight either call it good or try a different powder or a different bullet.

At least now you know what you're up against COAL wise.

Generally, a shorter jump to the rifling can be easier to find a good load.
That being said,.. long jumps to the rifling can also be accurate... But not always on the first try.
You might have to try a different power and/or bullet to turn mediocre groups into a happy rifle and shooter.

Weatherby's are usually quite accurate hunting rifles.

Good Luck and happy shooting !

 

[Kenneth66]

Thanks to all . Tried 5 three shot groups yesterday , with H4831 74.5 gr . Had some 20 year old CCI magnum primers , I was a bit worried about them , but they had been vacuum sealed and was the only magnum primers I had on hand , turned out ok .
I picked the powder charge because it was in the middle and H4831 and IMR4831 are the only two slow burning powders I have . The H4831 was as old as the primers , but again it worked fine .
We're I screwed up was I forgot to write down the OAL , but it was only a couple thousands over 3.560" as that was as long as I could get them and still feed from the magazine . 3.560" is the Sierra recommended length for 180 gr bullet .
The bullet I used was 180gr E-tip .
Fired one fouler and produced four three shot groups that were an inch or slightly under with the last group 1.25"
The 74.5 gr that I picked for a starter load was middle of the pack . So , I felt I got pretty lucky with the start load , especially with old components .
Next weekend I will bump it up to 75gr and increase .5 gr with each test .
Hopefully it will get better as I would like to be able to take advantage of the velocity it is capable of .
That 180 gr bullet sure does put a lot of shank in the case though .
Kenneth

 

[Danny1788]

Buy some imr7828 its the cats meow in 300WBY

 

[Kenneth66]

Yep was looking at the Nosler load data earlier . They say it's the most accurate powder they tested with 180 gr E-tip . But it also said test were done with a pac-nor 26" barrel .
Is it fair to assume the pac-nor barrel won't have the long Weatherby throat ?
Just asking questions , as I plan to purchase some 7828 this week if Cabela's has it in stock .
It seems to be a favorite with a lot of people in that caliber , will be interesting .
Kenneth

 

[JRS]

Yep was looking at the Nosler load data earlier . They say it's the most accurate powder they tested with 180 gr E-tip . But it also said test were done with a pac-nor 26" barrel .
Is it fair to assume the pac-nor barrel won't have the long Weatherby throat ?
Just asking questions , as I plan to purchase some 7828 this week if Cabela's has it in stock .
It seems to be a favorite with a lot of people in that caliber , will be interesting .
Kenneth

PacNor probably chambers to SAAMI specs.

 

[Danny1788]

Mine is a factory WBY vanguard 24" barrel and my buddy uses it with his mark v 26" barrel. 300wby just likes 7828 in my experience

 

[Kenneth66]

Called Cabela's , they don't have it at the Gainesville store . Tomorrow I will call some local shops and see if they got it or order it . Should have had Cabel's store order it , probably would have been there by end of week . Oh well , you know what they say about hind sight .
Kenneth

 

[MagnumManiac]

Ok , that's a relief to know . But a little confusing , as I have always been taught the less bullet jump , the better .
So , I guess I just start at the longest OAL that will work in the magazine and look for a sweet spot ?
Edited for an after thought , would it be reasonable to put less concern in the OAL and try tune with powder and powder wieght ?
Thanks , Kenneth

Yes, this is what I do, just seat to max mag length and most bullets will shoot a clover leaf with some powder tweaking. You need to tune the barrel harmonics.
As the freebore should be running .0005” over bullet diameter, the tuning comes from the powder charge.

Cheers.