Chamber demension 416 Rem. Mag.

[ralph76]

Where can I find chamber demensions of a Winchester M70 Safari grade in 416 Rem Mag? I'm interested in the rifling leade length.

 

[NCsmitty]

That may be difficult to attain, depending on the age of the M70, due to the ownership changes of the Winchester name. Although someone may have it.

If you are in a position to be able to check the leade length yourself, it can be done by using the bullet that you wish to use and a lightly sized case so the bullet will slide under a little pressure, and hand seat the bullet long and chamber the powderless round. Do this several times to get an average of the COAL with that bullet. Different bullets will give you different readings due to the bullet's ogive.
You will need to seat the bullets .020-.050" deeper than the established leade distance using the empty case/bullet combo, to keep pressures down.

This may not be what you're looking for, but I hope it helps.


NCsmitty

 

[ralph76]

Thanks. I went to SAAMI and got an idea there. The reason I'm asking is because I have a old Winchester M70 that was rechambered to 375 Weatherby. It has a 3/4 " free travel before it encounters the leade of the rifling. It does 2 inch groups at 100yds. but no better. I haven't shot it at 200 yds yet, but I'm concerned it won't do good. I'm just researching now, but want to go to Africa with a accurate gun. Am I taking this to far though?

 

[rcmodel]

Seems doubtful the free-bore is the problem.

All Weatherby calibers in all Weatherby rifles have what is considered excessive free-bore in other rifles & calibers.

They do it to control pressure, not only during normal shooting, but in extreme temperatures, in Africa for instance.

I think I would investigate jacket fouling in the bore, a damaged crown, loose scope mounts, a marginally bad scope, loads or bullets the rifle doesn't like, or a stock bedding problem before I got too concerned about the Weatherby free-bore causing accuracy problems.

And no doubt about it.
A .375 Weatherby isn't the easiest gun in the world to shoot tiny groups off a bench with!!
I don't care who ya are.

rc

 

[ralph76]

Seems doubtful the free-bore is the problem.

All Weatherby calibers in all Weatherby rifles have what is considered excessive free-bore in other rifles & calibers.

They do it to control pressure, not only during normal shooting, but in extreme temperatures, in Africa for instance.

I think I would investigate jacket fouling in the bore, a damaged crown, loose scope mounts, a marginally bad scope, loads or bullets the rifle doesn't like, or a stock bedding problem before I got too concerned about the Weatherby free-bore causing accuracy problems.

And no doubt about it.
A .375 Weatherby isn't the easiest gun in the world to shoot tiny groups off a bench with!!
I don't care who ya are.

rc

Thanks. I knew about the freebore and the thought Roy had about that. I have though put bullets .002 thou. off the rifling and drop the charge 10% and got much better results. That was my thought for the rifling.

 

[NCsmitty]

I have though put bullets .002 thou. off the rifling and drop the charge 10% and got much better results.

If you have to do that for better results, then you're just wasting your time, and you should have left it in the original 375 H&H chambering. Setting the bullets at .002" off the lands is foolish and perhaps dangerous as the bullet tolerances are greater than the .002" that you think that you're using. Dropping the charge 10% gives you 375 H&H power level, so what have you gained?
2" groups at 100yds should be more than adequate to take even dangerous game, and I have no idea if you have tried a selection of different bullets to see if you can improve your groups at full power loads. This is not a benchrest style rifle in that caliber, although it's accuracy is quite adequate, 1" and under groups will be hard to come by.
We have not even touched on your ability to shoot the stout recoiling caliber, because we just don't know.

I wish you luck with your hunt, and deciding your next move.


NCsmitty