Home Forums Reloading Big Game Rifles 7mm brass for 257 wby

I decided to make some 257 wby brass out of new 7mm rem mag win cases. I simply ran them through my rcbs 257 wby full size die set all the way down against the shellholder for a full sizing. my question is... In my haste I think I should have only sized them until they slightly crush fit in my vanguard rifle. When I fire these cases--Will I have any case stretching or headspace issues since I did not size them to my chamber but instead just fully resized them? I was planning on backing down the load several grains due to difference in capacity vs the wby case. Was going to form with 68 gr RL22, fed 215, hndy 100 gr sp. I just wanted some good cases formed after this first firing. I usually just use wby cases but was interested in doing this since I hear of others having good luck with it. Win cases are less than half the money. My wby brass seems a little on the soft side also.

That excess brass had to go somewhere. Check the neck wall thickness. You may have to ream/turn the necks.

I formed some 7 M/M Rem. brass for my 7 M/M Wby., but the neck came out shorter than the Weatherby brass. I didn't use it because I was concerned about erosion in front of the neck.

Both cases are belted, so you shouldn't have any headspace problems, unless you are talking about the distance from the base to the shoulder, but fire forming should correct this. As for stretching, the only way to know is to measure them.

One way to determine if the necks need reaming or outside turning is, after you fire one, before resizing, try to start a .257 bullet into the case mouth. If the bullet is a free fit, then you are okay. If the bullet binds, that means that the brass is too thick and too tight in the neck in the chamber.

What this means, when you fire it, the neck cannot expand to release the bullet. Or, it can also mean that the case has stretched and the mouth is touching the origin of the throat, again not allowing the case neck to expand when firing.

In the first instance, reaming/turning is called for. In the second, trimming to correct length.

I don't know the chamber and cartridge specs. of your rifle, but you can seat a bullet in your formed brass, measure the diameter of the neck, subtract .257, divide by 2, and this will give you your neck wall thickness.

Do this on a .257 factory load, if you have one, and compare the neck wall thickness to your formed cases.

I have a ton of 7mm rm brass as well and wouldn't it be fun if I could use it for fowling shots with cheap bullets instead of using wby brass. I resized a 7mm rm case and the case measured 2.489 inches. Weatherby brass measures 2.539 inches. The difference being .050 which is not exactly a thou or two. I decided against using it for the same reason 1234567 mentioned since that .050 infront of the neck would get flame broiled everytime you light one off.

There is a better way to check for necks that are too thick. Measure the diameter of a case that has been fired in that rifle. It will have sprung back maybe .002" from the chamber neck diameter. Now measure a loaded case with your new brass. If is not at least another .002" smaller, then things are tight.
Measuring the walls with a tubing mic also works. So does measuring the loaded diamter of a factory case as compared to a loaded diameter of a reformed case, just like 1234567 suggested.

But with a high intensity round like a 257 Roy, it is better to figure this out without shooting to test safety.

I shoot BR rifles, and it is common practice to turn cases to only a couple of thou under the chamber, but that is getting pretty tight.

Ok, I measured the neck of 257 wby formed 7mm RM win case loaded w/ bullet seated @ .283 in. I then measured empty fired 257 wby case @ .286 in. That gives me 3 thou. Tight but not too tight. You guys do bring up a good point in that the necks are quite a bit shorter on the formed brass; effectively making throat area out in front of it. I should have tried chambering a empty reformed case in my gun before expressing concern over headspace in front of the shoulder and case stretch. Turns out this reformed batch all chambers with a little crush, not bad but just a little resistance when closing down the bolt. The rifle is a sub-moa vanguard. I planned on using my wby brass for some loads I have developed and the reformed 7mm brass for other loads. When and if the bbl gets smoked it will get a 26 or 28 in replacement. Only have about 80 down the tube so far, plenty of shootin left. Maybe I'll try to stick to ball powders for the reformed brass as that is supposed to cause less throat erosion. Or is that a wives tale?

Also, I just measured the neck of a factory wby 257 loaded round @ just barely under .283 and the formed win case at .283 dead nuts. The difference looks to be about 2 ten thousandths. I think thats not of concern now either considering these will be fired from a factory chamber and not a tight necked bench gun.

Your factory cartridge has a neck wall thickness of almost .013, about 2 ten thousaands, as you stated.

"the formed win case at .283 dead nuts."

Is this measurement with a bullet seated? If so, then the neck wall thickness is .013, almost like the factory cartridge, and should be okay.

IIRC, the .30-06 brass I have measured was about .015 neck wall thickness.

Different cartridges might have different specs. for wall thickess, but you should be okay, going by the thickness of the .257 factory cartridge.

I have two boxes of 7mm WB, appears to be once fired but not sure as I got these in a trade. A picture showing the boxes is in the classifieds. I will take $25.00 shipped. PM me if interested.

Ivan

yes the reformed win brass was measured with a bullet seated as to compare to a factory wby 257 loaded round. I think it will be ok. Thank you so much for the help and feedback to all who responded. This is a great resource to sort things out sometimes.

I have used 7MM Mag Brass necked down with no problems in my Vangard SMOA, I have also used 264 Win Mag necked up with no problems. Just size, square the necks and fire. There has been no safety issue, frequently the first firings are sub moa. I've been doing this for years. Check with Rick Bin to verify this as he does the same for his 257Roy as do others on this forum.