Casting for 378 and 460 Wby and very long freebore.

For those of you not familiar with the 378 and 460 Weatherby they both have a very long parallel freebore. The rifling starts about .75" from the case mouth. When properly made the diameter of the freebore is about half a thou over bullet diameter.

I can get moulds made in Australia and was wondering if such a mould should cast a bullet than ran bullet diameter for about its full lenghth so as there would be only a small amount of freebore with a loaded round.

Also, what about paper patching. My understanding is that with paper patching the bullet is made to bore diameter and the paper patch takes it up to groove diamter. Any suggestions in the paper patching area for the very long freebore.

Mike

I have had problems with "well used" military where the throat is extended from a large amount of FMJ shooting. Usually the fix with cast bullets is to use a bullet that will seat out far enough to just "kiss" the rifling. this will center the bullet and very good accuracy is the norm.
As far as paperpatched cast bullets go I've done a little experimenting with 45/70 and .458 Win. We had a group buy a while back and had some .45 paper patched moulds made. The guns I'm working with don't have a lot of freebore. With the same long seating you should get good results the lower pressures that you use with cast and paperpatched bullets negate the need for freebore. In full speed jacketed bullet loads the freebore is supposed to keep the initial pressure down but still achive the high velocities that weatherby shooters like to bragg about.

Hope this helps.

Mike, the gun should be OK. Use a boolit the same diameter as the freebore or .001" over. I would not worry about getting close to the rifling. The accuracy will depend on the length of the boolit the twist likes. Shoot it and have fun, keep us posted.

Mike...there are two solutions to the .460. I had a .458 Win Mag Number 1 Ruger. Had a throat about 1/2 mile long. The old Lyman 462560 (if you're lucky enough to find one) shoots pretty well in it as does the 45-500-FN RCBS. Now, both of these cast at about .458" and I "beagled" them to about .463" and sized to .462" and they shot pretty well for me. The 560 is a bore rider and runs about 545 grains. The RCBS has a short nose and has to be seated way out but either of these will probably work but may not feed through the action.

Also, you may have to open the seating die to take a bullet this big in diameter and that's no easy task.

You may be able to paper patch some up to fill the freebore but that is a lot of work. Paul Matthews has written a lot on paper patching the .458 Win Mag Ruger Number 1s and you'll have to decide whether it's worth the effort.

Forget shooting light 300 grainers in it. Just too long of a jump. You may get plinking accuracy by using a dacron filler but I don't like to use filler if i don't have to./beagle

Paper patching brings the lead slug up to bore size. Cast bullets for patching are smooth sided, no lube grooves. The patch makes two turns around to projectile, ending up at the right size. You cannot take a 458 bullet, wrap it twice with .002-3 paper and get in the chamber. If you can find the book call "The Paper Jacket" it will give you all the details you will need. Maybe BAW has a copy?

Hog Killer

I was thinking of killing two birds with one rock.

If I had a mould made than ran full diamter for most of its length so it effectively removed the Wby freebore that exist in 378s and 460s that would also add to flexibility in loading due to ignition.

We don't get that Accurate Arms powder, is 5744 or a similar number, which appears to be a shot gun type powder but with maybe 4227 burn rate. In the 378 and 460 you can load down to about 375 H&H or 458 Win easily and with top accuracy...but to go much under that you hit hangfires areas unless you drop back to shotgun powders and then you are in the 1300 f/s area.

I understand with the paper patch that your bullet is at bore diameter and the paper brings it up to groove diamter.

Mike