What if I built a rifle, say a 340Wby, with a much shorter throat than standard? I like seating closer to the rifling than the Wby freebore would allow. I'm considering a reduction that would give a 250gr Partition proper grip in the neck and be just off the rifling.

If I did this, would load data be affected? If so, how. Would this change affect the cartridge's performance negatively?

IF all this is a good idea, how much of a reduction in freebore would be advisable? Thanks for any enlightenment.

I'm no expert but I believe that the excessive freebore is to keep pressures sane with some otherwise insane loads.

I have seen disclaimers accompanying weatherby mag load data stating that the data is only to be used in original Weatherby and A-Square chambers because some custom chambers will produce excessive pressures due to lack of sufficient freebore.

The big W cals are made with this in mind freeboring eases up the initial pressure build up and gives greater velocity. You might do it but then if you ever sold it to a non reloader, it could cause problems. My opinion, don't.

Yes, I believe the freebore to be an integral part of the Weatherby chambering for those reasons. Accept the freebore and work with it. They're still capable of excellent accuracy. Otherwise, go to a different cartridge.

My pet 300Wby has a "custom" throat. It's long enough to permit the use of factory ammo w/o the high pressure problems but does give a very positive effect on the accuracy.
Load data for normal Wby chambers is out, reduce everything by 15% and work up slowly. I won't post my loads because my chamber and barrel spec's will likely be a lot different than yours. They are less than manuals indicate for the normal Wby. If your gunsmith is close by you can chamber it and then ream the throat portion separately, going deeper as trials are conducted. Too short and you have a 300Win that burns a lot more powder, too long and you get a standard Wby. If you don't get it too short you could/should end up with something like mine and be able to use factory ammo in a pinch.

I had my 257wby rebarreled with a short throat and the groups shrank to less than half the size of those with the factory barrel.I did have to reduce my loads by a couple of grains and did lose 50fps but the accuracy improvement was well worth it.

Weatherby factory ammo is somewhat anemic when compared to what was sold in the 60's and early 70's. One of the reasons is there are so many rifles chambered in these calibers that Weatherby has no control over as far as the freebore issue. Personally, I don't think the freeboring hurts accuracy any. My Weatherbys that are freebored are every bit as accurate as non freebored calibers that I own. While seating out to the lands will increase accuracy in some rifles, I've found the opposite to be the case in others. It isn't a issue that is required in every rifle. Bill T.

Work with the long throat, it's there for a reason on Weatherbys. A friend of mine had a 257 built with a standard throat and he had to reduce his loads considerably and lost a good deal of velocity. He might as well have a 25.06.

I have a 257 Ultramark that I bought in 1989 and it STILL shoots 3/8" groups AND attains advertised velocites jorge

Understood. I won't mess with the throat on Weatherby rifles. I had to ask the question. My ignorance has been cleared up. That's why this forum is so brilliant. Thanks.

My own short throated 257wby still produced 3500fps with 100gr bullets.I haven't seen a 25-06 do that.Weatherby uses the long throat to gain a bit more velocity and while it does not always decrease accuracy it often does.Using a shorter throat will most usually require that you change your loads slightly but it will not cause the hundreds of fps loss of velocity that others would have you believe.You have the choice of believing the assumptions by people that have never tried a short throat in a weatherby chambering or you can believe the people that have actually done this.The choice is yours to make.My own 257 weatherby lost a grand total of 50fps with the shorter throat but due to differences in barrels the results can vary .Even changing to another long throated barrel could require a change in loads and most likely will result in a gain or loss of velocity again due to differences in barrels.
If you decide to go with a short throat and don't like the results you can always lengthen the throat with a throating reamer.It isn't nearly as easy to shorten a throat.

[ 11-08-2003, 23:55: Message edited by: stubblejumper ]

Gonzo, read the below post and look carefully at my second reply, note the 84,000 psi statement!!!!!

http://www.nookhill.com/ubb/ultimatebb.php?ubb=get_topic;f=38;t=001509#000025

Here we go, Archives in action!

Actually unless you are going to be using factory loads there is no problem with pressure.You start with a reduced load and work up your loads looking for pressure signs like any other cartridge.Or you could build a 338rum instead ,gain more velocity than the 340wby and freebore won't be a concern.

I wouldn't build a rifle for a caliber available in factory loaded ammo that couldn't be safely used with that factory ammo. I could well go belly up at any time, and someone might well end up in posession of that rifle who wouldn't know any better than to use factory ammo. Resale might be an issue for some, but I never sell my guns and hope never to have to.

It's not that often where there's a post that I can relate to as directly as this one.

I had my 30/378 Mark V rebarreled by Shilen a few years ago to 338/378, with a standard if not short throat. I know some folks have already disagreed with this, but having actually shot a gun big Weatherby with a short I can tell you there's no problem with it. I will say that my rifle should only be fed handloads, but I can acheive the same velocities as a factory gun and do it with less powder. The only thing the freebore does is reduce the pressure which means you've got to add more powder to get the pressure back up, and the whole accuracy thing is a full topic in itself. In short, don't be afraid to go with a shorter throat if that's what you want.

[ 11-10-2003, 06:08: Message edited by: Kingfisher ]

If you eliminate the freebore, loading data CERTAINLY IS AFFECTED!! The reason for the freebore is to let Weatherby attain velocities at safe pressures that could not be achieved with safe pressures without it! Note the glaring contrast between 7mm Rem. Mag. and 7mm Weatherby data, despite the fact that both have about the same case capacity! What's the difference? FREEBORE!!

Everyone has a different opinion on the whole freebore discussion and my hope is to not start a war with this, but I wanted to discuss this further. The 7mm Rem Mag vs. 7mm Wby example doesn't really work since the case capacity of the Wby is about 13% higher +/-. The respective velocities are in turn about 13% higher. The freebore is just for safety. If you remove the freebore and change your loading technique and use different powders you can do everything that a freebored barrel can do, and do it with less powder. Does all of this mean that I can't fire factory ammo, yes, but for me personally, that's not a problem.

To me, it's irresponsible to build a rifle in a factory chambering that can't fire factory ammo safely, unless you can assure that it will never fall into anyone's hands who's unable to handload its special downloaded ammo.

Pretty much what I already said, just stating it more plainly. Y'all are doing a dangerous thing. Won't be you that risks injury, you'll be gone, but you're leaving a booby trap behind.

That'd certainly help.