257 wby question from another forum but..

Odawgp

An interesting question none the less, as I also have a 257wby


predatormastersforums
quote:I am running 7mm rem mag brass thru a 257WBY full length size die. It looks great but ends up about .05" shorter than the recommended trim length for the .257WBY. Is this something I should worry about? It is a Weatherby rifle. So it should have a lot of freebore. Do I need to worry about advanced throat erosion? Or should I just go ahead and shoot it? Will the brass eventually reach the recommended length? Thanks for your help!!

perry shooter

More then likely it will get longer and and need trimming after few times .050 should cause NO problem on the first firing.

nononsense

Odawgp,

"It looks great but ends up about .05" shorter than the recommended trim length for the .257WBY."

This is not surprising since the 7mm Rem. Mag. case is 2.500" in length and the Weatherby case is 2.560" in length. The case will not get longer when you're trying to compress it into another shape.

"Is this something I should worry about?"

Maybe, maybe not. It depends on the rest of the chamber in front of the neck.

"So it should have a lot of freebore."

It does, to certain extent. But it's not the freebore (leade) that is a potential problem.



The problem has a red square around it. This is named the 'Transition Angle' which is a 45 degree angle that acts as the step down from the chamber neck diameter to the chamber leade diameter. The length of the neck area in the chamber is always a little longer than the actual neck length of the cartridge case. The problem with this area being 0.050" longer yet is that it can become an area that collects fouling and carbon. In the shorter version, the plasma jet or stream usually misses this area. But, make this area longer (further away from the end of the neck) and the plasma not only impinges on this step but makes this area more susceptible to collecting fouling and worse, carbon. This can contribute to a building of pressure that may not be immediately understood.

"Do I need to worry about advanced throat erosion?"

Throat erosion is a factor of the plasma temperature, the angle of impingement and the type and hardness of the steel used in making the barrel. These cases minimize the angle of impingement and the temperature can be partially controlled by powder selection and balance with the bullet weight.

"Will the brass eventually reach the recommended length?"

Highly unlikely. Growth is experienced when a case has someplace to grow. So if the chamber has more space from the first radius up through the end of the neck, the case might grow. This is a problem that occurs with resizing. Don't set the shoulder back while resizing. You will eventually see case separation just above the belt if you do. Know the length of of your chamber and set your dies correctly.

Cases will usually grow when the design features a shallow shoulder like the .30-06 or the .220 Swift. The double radius Weatherby shoulders curtail case growth.

Best.

Mobuck

Actually, the 264 Win Mag brass is easier to neck down than 7mm Rem mag. As long as you pay attention to correct case body length there shouldn't be a problem. Normally the headspace is controlled by the belt but for best case life the case should contact the chamber shoulder. Using the 7mm case will probably result in the need for neck truning or reaming. I would suggest using a moderate load to fireform the brass before loading full power. In my experience the Weatherby brass (Norma) is pretty soft compared to Remington brass.