[Ratzo]

Hello, although I am new here I have been reloading and shooting for 30+ years. I came across something new yesterday while velocity testing some .257 WBY loads that I have never seen before. Rounds # 2 and # 9 have these unusual dents at the shoulder. Of the 10 rounds fired all the cases but these two look normal. The brass used was new and unfired. The velocity averaged 3255.

This particular rifle does not have the Weatherby freebore and the load used was 60 gr. RL22, Federal 215M primer with the Berger 115. There are no visual pressure signs on the cases.

Again, I have never seen this and wonder if any of you know why this occured.

165889

[Arkansas Paul]

Wow. I've never seen that. Hopefully rcmodel will come along soon and enlighten us. If anybody here knows about it, it'll be him.

[rcmodel]

Low pressure load.

60.0 grains RL22 is below the suggested starting load in the manual I looked at.

Low chamber pressure fails to expand the case neck enough to get a chamber seal and pressure & unburned powder gets on the outside of the case and blows a dent in it.

Bump up the load before something worse happens.


PS: It could also be caused by work hardened case necks if the cases have been reloaded several times.

But for one reason or the other, the cases are not expanding enough to seal the chamber.

rc

[Arkansas Paul]

Told ya.

[Jim Watson]

Agreed. But don't escalate too fast, the lack of freebore will probably limit how heavy a load you can use.

[243winxb]

Did you clean your brass before the photo was taken?? The Collapsed Shoulder is in an old Speer manual. Light loads & slow powder are the cause. Use a faster burn rate of powder. Pressure is low & neck not expanding to seal. Make sure the bullets have enough neck tension. The expander (if using one) should be .002" smaller than bullet diameter. This will keep the bullet from moving when the primer fires. The bullets bearing surface should be in full contact with the neck. If seating the bullet long to get close to the lands/rifling there may not be enough shank of the bullet in the case neck.
http://thefiringline.com/forums/showthread.php?p=4928827#post4928827 http://i338.photobucket.com/albums/n420/joe1944usa/Firearms%20%20and%20%20Reloading/th_257Weatherby.jpg (http://s338.photobucket.com/albums/n420/joe1944usa/Firearms%20%20and%20%20Reloading/?action=view&current=257Weatherby.jpg)

[Ratzo]

Thanks for the replies. Pressure was my first thought as well. But without the carbon staining so often seen (no I hadn't cleaned the cases) I was confused. I spoke again with the gunsmith who built the rifle about the throat. The chamber was cut with a reamer designed to allow a 120 gr Nosler partition to be seated sufficiently deep and still be .050 off the rifling. Obviously no freebore. He has chambered 6 rifles including mine. Typically loads for this rifle are 10% below minimum charges for Weatherby data. As I worked up these loads, I used typical indicators of pressure. With a magnifying glass In the right light, I can barely see marks from the ejector cut in the bolt on the casehead. (Sako AV action)

The two rounds that dented chronographed 50 fps faster than those that didn't so pressure should be higher. That points to hard case necks that are not expanding=more bullet/neck tension. I measured the neck dimentions of the 10 fired cases. The two that dented were .002 smaller both inside and out. .258 vs. .256

Correct me if I am wrong but if I am getting consistant velocities that are typical for the cartridge/bullet combination, how can my pressures be low?

I will go the annealing route and see what happens.

Again thank you all for your input.

[243winxb]

The brass used was new and unfired. Fire formed brass, with minimum shoulder set back on sizing, may help. The two that dented were .002 smaller both inside and out. .258 vs. .256 Sign of low pressure, unless you have a tight neck chamber. 60 gr. RL22, Federal 215M primer with the Berger 115. This load may be as much as 9.0 gr under maximum. See Steves pages http://stevespages.com/page8a.htm No free bore, but jumping the bullet .050" same as free bore? Strange that the fired brass is so clean. Different component=Different pressure. The bearing surface of the bullet can have an effect on pressure. Less bearing surface=less pressure. Are the bullets coated with anything like moly? This would produce less pressure also. Let us know what the fix is.

[Ratzo]

243, No coatings. The smith tells me it is infact a very tight chamber. Those measurments I quoted were inside neck measurements. Typically when sizing for just one rifle I take the bolt apart and size the case until it just allows the bolt to close. That is where I lock the sizer in. As for load data Berger should publish a manual, but they don't. I gathered info from several sources on similar weight bullets and went from there. I found it interesting that Hornady's manual #5 listed a minimun load of 56.3 for their 117, and 51.8 for their 120 with RL 22. That in a Weatherby chamber. Based on that I don't think I am in danger of too low of pressure. Anyway I have to go see my smith next week on another issue with a different rifle and will talk with him more.

Thanks, and I will let you know how things shake out.