257 Weatherby, Part 2, seating depth adjustment

[Dr. Vette]

If you recall I did some initial development for charges about a month ago. I settled on the 68.5gr charge of 7828SSC for the test below.

The original thread is here:
http://forum.nosler.com/viewtopic.php?f=4&t=27619

As a reference, the factory OAL is 3.142-5 or 3.160 depending which box I look at. Most were the shorter length. I use BTO (base to ogive) length, and I found that my loads in the first thread were 3.231 OAL or 2.718 BTO.

I made 3 loads each of 2.720, 2.690, 2.660 and 2.630 measuring the BTO on each, seating with a micrometer die so that each was exactly the same. Brass is from this rifle, trimmed, body die sized and then neck sized.

Data:
2.720 - 3387, 3385, 3407
2.690 - 3426, 3402, 3409
2.660 - 3406, 3419, 3420
2.630 - 3400, 3423, 3414*

*last shot had a slightly looser neck, which I noted immediately upon loading the round. This may have been a confounding error...

As you can see from the photos below, no true winner emerged.
The targets are top row 2.720/2.690/2.660 and the 2.630 was the middle of the bottom row. Groups are up and left compared to the bullseye, but I'm not worried about that. Targets were at 200 yards.

Up until my last shot of the 2.630 which was also the one with the looser neck I thought that round might be the one. However, I'm not so sure.

Any thoughts as to what I should do next?

Patrick

 

[SJB358]

Patrick, can you continue to shorten them in COAL? Not sure how short you are already, but maybe running them down short will show you something else. Seems like your groups are all about the same and not really all that bad for 200 yards, but it looks like they wanna go shorter.

 

[rodell]

I would definitely try a little shorter. That load of SSC isn't going to spike.

Two questions: Are you shooting the groups round-robin? How much cooling time between shots?

I'm interested in your "loose neck" observation. It would have to be very loose to notice, I'm surprised it make it to the target.

 

[Dr. Vette]

I would definitely try a little shorter. That load of SSC isn't going to spike.

Two questions: Are you shooting the groups round-robin? How much cooling time between shots?

I'm interested in your "loose neck" observation. It would have to be very loose to notice, I'm surprised it make it to the target.

The shortest one here seems to be very short, and I'm nearing the end of the bearing surface.

Groups are shot round robin, and I have A/B/C cartridges made for each OAL.
A minimum of 3 but more likely 5 min between shots. I was shooting another rifle and helping Dad spot his shots from his 22 as well.

These 257 Wby rounds are collet neck sized using a 25-06 Lee collet. It works, but I think that I might want a size larger for the collet. I find the same with the 300 Wby loads I just did for someone else using a Lee collet, though ironically have no issues with the 7mm Rem collet on my 7mm Weatherby. In both the 257 and the 300 it takes a fair amount of pressure to seat the bullet, and with each I have one case where the shoulder collapsed. This was even using new Nosler brass for the 300. So, when the last one slipped in with ease I knew it was a LOT different than the previous 11 loads.

I have a Redding neck bushing die as well, but in checking neck wall thickness I had far better results using the Lee collet die than the Redding die. So, I stuck with that. I have not yet had a chance to check a loaded round from each method to see which has the best concentricity. However, my assumption was that a straighter neck would result in a straighter loaded round.

I forgot to use neck lube on these until after the first few were already loaded, then didn't after that as it might have thrown the results. Normally I do that - it was a brief lapse on my part.

 

[SJB358]

Patrick, I think your probably close. I just ran into the same problem as you with my 35 Newton. I was going nowhere with the 225 AB's seated out near the rifling and not getting anywhere going back till I was at the point of almost loading past the ogive, so I went in smaller increments and found the spot. I shot these round robin the same way you did yours, so you know the feeling when you come around for that 3rd shot on the last target when you have two holes next to one another!

 

[nvbroncrider]

Man Scotty the Newt is a beast!! Do you like the barrel? Foul much?

 

[SJB358]

It is doing really well Jake. I shot it at first with plain old Sierra's. Fired about 35 rounds of that stuff, cleaning it twice in there. Then, when I started load work it took 4-6 rounds to settle back in. Now, it seems to be fouling very little. Once I verify this load, I will clean it again as it will be another 40 rounds or so through it. Then, I will take it back out and see how many it takes to settle back down. JES does a good job. The rifling is crisp and clean and it shoots, once I found where the bullets wanted to be. I was kinda getting a little antsy since it wasn't turning in what I thought were decent groups. Turns out, it was more about seating depth than anything else. Pretty sure it will be a keeper. I love the rifle to tears. Just a animal.

 

[Dr. Vette]

Patrick, I think your probably close. I just ran into the same problem as you with my 35 Newton. I was going nowhere with the 225 AB's seated out near the rifling and not getting anywhere going back till I was at the point of almost loading past the ogive, so I went in smaller increments and found the spot. I shot these round robin the same way you did yours, so you know the feeling when you come around for that 3rd shot on the last target when you have two holes next to one another!

Wow, major difference for being such a small change in length!

I may now have to play with them a bit and see if I can nail it like you did, unless other suggestions develop.

 

[SJB358]

I was starting to get worried but the bullet wants to shoot where it wants to shoot. This one taught me that in spades. I thought I had the AB's licked, but in this rifle and occurrence it wanted more jump than I have found in a few other rifles. I would say take your shortest length and work shorter in .010" and see what comes of it. Run it to the ogive. I am very close to the ogive on the load that shot so well and was worried if these loads didn't shoot I would have to fine another bullet.

Some rifles and bullets run us through the ringer, but seem worth the work once we nail it down.

 

[DrMike]

It is certainly true that small changes in seating depth can make a major difference. I have had a few rifles that were sensitive to as little as 0.005 inches of differential. I'm talking of moving from MOA to 0.10 inch accuracy. Pretty dramatic.

 

[Dr. Vette]

Any recommendation as to what direction to go (shorter or longer) and how many?
I'm tempted to get as close as I can to the factory BTO length as I can shoot those under an inch at 200 yards. Does that make sense?

 

[SJB358]

I would keep going shorter till you can't go any further.

 

[rodell]

I would keep going shorter till you can't go any further.

I agree.

 

[boomer68]

Just picked up an Accumark in .257 and this is a good thread to keep an eye on

 

[Darkhorse]

I would load another set but this time instead of .030, I would split the difference and seat .015, or right between what you've already recorded.
My 7mm is real sensitive to small seating depth changes so my tests are at .010 changes in depth. Then I'll go to .005 if the data warrants it.
I would also load a few sets closer to the lands as your rifle might want to go deeper.

 

[Dr. Vette]

I would load another set but this time instead of .030, I would split the difference and seat .015, or right between what you've already recorded.
My 7mm is real sensitive to small seating depth changes so my tests are at .010 changes in depth. Then I'll go to .005 if the data warrants it.
I would also load a few sets closer to the lands as your rifle might want to go deeper.

I read this and I'll be honest - this is what goes through my head....

How many shots does it reasonably take to arrive at an accurate load? To go 0.010 all the way through what I initially published is 36 rounds, then going shorter can easily add another 24? This would have to be split into at least 2 range days given the time of year and sun, and it's not over yet. 100+ shots to arrive at an accurate load? And you wonder why my shooting partner says I should just buy factory ammo that will shoot under an inch in this rifle and go from there.

My plan is to do this -
I'm going to copy the exact base-to-ogive length of the couple of boxes of factory loads I have. One is a touch longer than my shortest test above, one is far shorter. I'll also test loads shorter than my shortest one above until I get to matching the shortest factory BTO length.

At that point one would hope something shows signs, and I can run up 2-3 sets at 0.010 difference.

I hope that sounds reasonable.

 

[SJB358]

Sounds entirely reasonable. I won't usually stick with a load that long before I change the bullet or the powder up to be honest. I ran through a ton of powders and such to try and get a 200 AB to shoot out of my 300WSM. Came up empty on almost all of them. Should have just ran with the 200 PT and called it a day. Did fine with those and a couple of different powders. Sometimes we just want what we want.

 

[Dr. Vette]

I would also load a few sets closer to the lands as your rifle might want to go deeper.

The longest loads above at at magazine length. Can't go any longer.

 

[Dr. Vette]

Sounds entirely reasonable. I won't usually stick with a load that long before I change the bullet or the powder up to be honest. I ran through a ton of powders and such to try and get a 200 AB to shoot out of my 300WSM. Came up empty on almost all of them. Should have just ran with the 200 PT and called it a day. Did fine with those and a couple of different powders. Sometimes we just want what we want.

I did the same for the 160 AB in Dad's 7mm Wby. 3 powders and 2 primers later I still didn't have it. Tried Bergers as well with no success.

I then tried Barnes 150gr TTSX and I had a load after one ladder test. Needless to say I didn't look any further.

The fact that the rifle can shoot this bullet well from factory loads tells me that it should be possible with handloads - it's just how to get there that is the question.

 

[SJB358]

Yeah, could just be a powder thing. Might be worth trying a different powder at your most accurate seat depths so far. You might get lucky.