I’ve loaded a ton of cases like .223/5.56, .243, .308, etc but never a belted bottleneck cartridge and nothing with such a different case/shoulder

Any advice for me and starting .257 Weatherby loading?

Not really hard with a good set of dies and being extra careful.

I've been reloading it for about 10yrs now.I haven't had any issues yet.Rare buckled case now and then.1or 2 per 200rnds.Be sure to trim them.

I'll average about 40rnds per year for practice,Really deads whitetails

Same here, Im a belted mag noob as well, and the 257 is even a little more of a challenge due to the rounded shoulder.

Im fighting through a couple of issues with feeding and bolt closing right now.  Just not adding up...

Link to THR

Would use a comparator to check how far out you can seat a bullet.  If a sized brass chambers with no effort, but adding a bullet keeps it from chambering, would check how long your free bore actually is.  When I used to deer hunt, used a 257 wby, and seated the Hdy 100 gn sp to 3.200.  Seated a Barnes 100 gn @ 3.285.

The Wby 100 gn sp factory loads were always more accurate than I could handload a bought 100 gn sp.  Then I measured the actual bullet diameters, and the factory bullet was larger dia.  Course this was 14 years ago. Used RL 22 and Fed mag primers almost exclusively.

Factory manuals for the wby's are all over the map, after lawsuit on supposedly factory overloaded 270 wby rounds (years ago).   Hornady dropped their load weights way down on the 257 and 270 wby loadings.

Sorry OP, not meaning to step on your thread, but some of what Im running up against might be valuable for you as well.

Thought about this, but my wonder at this point is do I have excessive neck tension with the 120gr bullets which is in turn squashing the shoulders out.  The resized and trimmed cases drop into the chamber, bolt closes easily, and they extract with no issues, like butter would be a good way to describe it.  The issue only begins as soon as a seat a 120gr Nosler.  Did the sharpie test on the bullet out at 3.300 COAL and Im not hitting the rifling with the Nosler 120s, so no really need to purchase the comparator case.  Besides, that freebore is what allows the 257 to bleed off the pressure before the bullet engages the rifling correct?

And you are correct, load data is kind of all over the place.  Hornady 9th is heavily lawyered at 61gr max for 7828.  Nosler and Hodgdon are right around 69gr if memory serves.  Lyman has no data for 120s in the 49th, but Lyman data is almost always hot.

Guess that is a possibility, but never had it happen to me when using Redding dies with a carbide expanding plug. How hard is it to seat the bullets?  From long ago in the fading memory department, some of the not wby factory rifles had shorter free bores and pressure problems with loads developed in a Wby factory chamber.   Wby long throating did allow higher velocities, but am not technically savvy enough to know if that involved higher/lower pressures.

Does your situation happen with any other bullets?  Are you using factory (Norma or Wby) brass?  Are you doing seating/crimping in one step?  Maybe a specific seating die problem?   Maybe try a dummy round that has been completely blackened to see what stops it from chambering?  Was the brass annealed?

The last loads I worked up with 100 gn bullets used 69 grains RL 22 for about 3500 fps from 26 in tube.  This is above many factory loads listed now adays, but believe the old IMR manual went up higher with IMR-7828 with listed/tested pressures.  Got about 4 full power loadings from factory brass, then scrapped it.

Weatherby factory brass, which is made by Norma if Im correct.  No crimps.  Bullets dont seem to seat hard.  Dies are RCBS.  Im not totally in love with RCBS seating dies, but they do work.

We have tested this rifle with 117 Hornady SPs, but decided to go to 120gr Nosler Partitions so they actually hold together at these velocities.  Odd thing is, the 117s feed and chamber with no issues at 3.300" COAL.

Ill have to do some testing tonight with a few dummy cases and Ill black them out and see where Im getting contact.

OK, solved the problem.

Long story short, the RCBS seating die that I previously thought was not a taper crimp die, was. That was messing up the shoulder as it over crimped. Backed the die out about and 1/8" from the shell holder, seated a new bullet in my dummy case, and it had no issues. It solved both the chambering and seating problem. Needless to say, Im used to Hornady rifle dies that do not have a taper crimp unless you buy them that way. Even still, totally my fault, and I put 2 and 2 together after I talked with a buddy, and we talked it over and he threw out some ideas. In short I should have RTMFM!

A couple pics

From left to right : once fired, sized, dummy, factory, and another reload. The only one that had issues was the dummy. Everything else chambered, even the once fired. Do you like my dykem in a marker? I figured the Magnum 44 is worth a laugh at least :)


You can see the shoulder hitting the chamber wall here where I marked it up.

Now some case measurement number for nerds:

Before I hit on the fact that the crimper was screwing me. Shoulders measured with Hornady 375 comparator

Once Fired:
OAL: 2.542
Shoulder: 2.120
Shoulder (across): .495

Sized:
OAL: 2.540
Shoulder: 2.115
Shoulder (across): .491

Dummy
COAL: 3.300 (wanted to see if this long COAL would hit rifling, it did not)
Shoulder: 2.108
Shoulder (across): .496

Factory
COAL: 3.043 (shorty round nose bullet)
Shoulder: 2.102
Shoulder (across): .488

Overall, lesson learned!

Glad ya worked it out.  Always enjoyed hunting with the 257 wby, and betting they got better bullets now adays.

Was totally a brain fart on my part.  Im just glad I didnt roll up the 15 rounds of test loads to find out they werent going to run.

Yup, we decided to go with a Nosler Partition.  They are pricey though at 70 cents each, but I really cant think of another bullet that would hold together other than maybe a Swift Scirocco or A-Frame when we will be seeing roughly 3300 FPS at the muzzle.

And this 257 definitely is a great gun for deer.  Ive never seen one run more than 20 yards after getting hit by it.  And the recoil is much lighter than it seems that it should be for such an overbore cartridge.

Thanks for the posts

Nothing really off topic since it’s all new to me with This caliber. Maybe I will run into some similar issues.

As far as the die  with the taper crimp, usually the boxes are marked with TC on the label and on the die body itself.  Just something to look for

I looked at the label, says notta about crimping, so I figured it was a dumb seater.  My favorite type.  But then this is a fairly old set of RCBS dies.  Only once my buddy asked me, and then I opened the instructions, did the light come on...  

The only thing I will say, and Ive seen this multiple places, is make sure you have a comparator to set your shoulder bump.  Use good case lube, Im using lanolin/iso at 18-1 ratio, and a heavy spray of it.  Or use something like Imperial.  Sizing wasnt hard, but the radius shoulders worried me.

This......and you might also see improvement in accuracy......

Glad you found it.  I did this with my .270 and a set of RCBS dies.  Since then, I use a comparator and just bump the neck back .001 for my bolt guns using RCBS dies.  I load my brothers .257WB

and have never seen this problem. Partly because since I found the problem (it was over pressure at low loads for that one) on my 270. I start by just running the die down to the shell holder and a

very small turn past (not even the 1/8 they suggest).  I'd like to get your load if you hit 3300fps with the partition. I think I'm up to 3200 with the Ballistic tip CT.