Ridiculous (BAD) SD/ES help

[TimeWillTell]

Shooting with a buddy today. He's working up a load for his FTR rifle with 185 Hybrids at 0.020 off in a custom 308 with a FTR chamber. Turned lapua brass and varget. Same lots of everything. He was getting decent groups but his SD in some loads was as high as 50 and ES as high as 100, 3 out of six charges. Best was SD 14 and ES 27, but that was just one in like 6 different charges.

He's experienced at reloading. For reference his 6.5 Creedmoor load work up today had SD in single digits in all but one load and 12 in the other.

Any ideas?

 

[Bradu]

A friend just went through this with his 243, his SD's were almost 30. I told him to try seating the bullets at a couple different depths and the next time we went to the range we hooked up the Magnetospeed and one of them was in the single digits. I think he tried at .020" increments if I remember correctly.

 

[Diver160651]

So he is jumping, correct?

My guess is his neck tension very low or not consistent. Ultra low neck tension workers if your soft seating, but not jumping.

 

[TimeWillTell]

Yeah he's jumping 0.020.

Adjusting seating depth was the first thing I suggested. I hadn't considered neck tension since he's using an undersized bushing and expander ball but still could be I suppose.

 

[Diver160651]

If you run super low neck tension and jumping, the primer can start moving the bullets providing inconsistent burn. Benchrest guys get away with it by seating with the jam into the lands. Getting 40lbs + when jumping, is key

But even more so problematic is inconsistent neck Tension...

 

[jg6.5]

I'm the schmuck TimeWillTell is referring to about this issue. I grabbed some measurements before I left the house this morning...

Redding FL Bushing Die
0.331 Bushing
Lapua Brass - neck thickness turned to ~.013" (don't have a vernier ball caliper, just regular calipers so not sure how accurate this measurement is)

For those playing along at home with their calculators, (~.013 x 2) + .308 = ~.334 --> ~.334 - .331 = ~.003 neck tension (supposedly).

I've been handloading for a while now, but this is admittedly my first foray into bushing dies and neck turning. Given that fact, my dumbass just realized that the expander ball measures .308" in diameter (.3075" if I close one eye and hold my tongue just right). I'm assuming this pretty much defeats the purpose of the 0.331 bushing, bring me back to almost no neck tension.

On that note, though, a sized case still measures out to 0.331 outside diameter. Don't know what to make of that.

Given the responses and what I measured this morning, this is probably more than likely a neck tension issue. I'm assuming a good place to start would be removing the expander ball and resizing, then trying my last round of charges again?

 

[Diver160651]

I don't know what press you are using for seating, but most eliminate all "feel" from the process. Seems the sweet spot for brass you jump is around 45-65 LBS. But it is easy to get swings from <20 over 100lbs. Without a way to measure, the best is to go slowly at the same exact speed and try to short them by resistance. If your at .331 outer neck on Lapua I have to assume you on the very high end of seating pressure.. so jump will not be the issue.. But variation can be.

FWIW the easiest way to measure without the proper tools is measure the neck of your LOADED round.. You might get a much larger number than you are expecting.

 

[jg6.5]

I don't know what press you are using for seating, but most eliminate all "feel" from the process. Seems the sweet spot for brass you jump is around 45-65 LBS. But it is easy to get swings from <20 over 100lbs. Without a way to measure, the best is to go slowly at the same exact speed and try to short them by resistance. If your at .331 outer neck on Lapua I have to assume you on the very high end of seating pressure.. so jump will not be the issue.. But variation can be.

FWIW the easiest way to measure without the proper tools is measure the neck of your LOADED round.. You might get a much larger number than you are expecting.

It's just a single stage rock chucker. Nothing has "felt" any out of the ordinary when seating, but the press has a pretty long lever on it so any small changes would hardly be noticeable, as you described.

 

[TimeWillTell]

I don't know what press you are using for seating, but most eliminate all "feel" from the process. Seems the sweet spot for brass you jump is around 45-65 LBS. But it is easy to get swings from <20 over 100lbs. Without a way to measure, the best is to go slowly at the same exact speed and try to short them by resistance. If your at .331 outer neck on Lapua I have to assume you on the very high end of seating pressure.. so jump will not be the issue.. But variation can be.

FWIW the easiest way to measure without the proper tools is measure the neck of your LOADED round.. You might get a much larger number than you are expecting.

His necks have been turned so he is probably light on pressure. My math tells me he may only have 0.0005-0.001 of neck tension.

 

[Diver160651]

His necks have been turned so he is probably light on pressure. My math tells me he may only have 0.0005-0.001 of neck tension.

Yes, that and over annealing can cause much the same..

 

[jg6.5]

Yes, that and over annealing can cause much the same..

Cases are on their first round of firing, haven't gotten to the annealing point yet.

 

[Diver160651]

There are a few issues with this video. But you can see the same Arbor press I use when I am really concerned about ES (ELR). Again, if you're in the lands, lower works great. But un-racking a live round can put you out of business hunting or in a match, especially if your running a jewel and a kernel drops in. In the video he is seating with VERY low seating.. Look for 40-55 with a 308 when running a lot of jump..

 

[jg6.5]

Thanks, I’ll keep that in mind if I’m still having issues.

 

[ZiaHunter]

If you plan on being competitive in F Class you will need to get your SD's in the low single digits. Controlling neck tension and charge weight to the kernel is critical. If you turned you necks properly there really is no need to use the expander plug and let the bushing control neck diameter. The only accurate way to measure neck tension while seating is using chamber seating dies with an arbor press with a PSI gauge such as Century 21 Hydro press. Also sort, trim and point your bullets. I sort all my rounds for a match based on seating pressure and since doing so has provided a very consistent water line. As Diver mentioned, jamming bullets can be very problematic in a match and have seen several rifles go down on the line when the round is withdrawn from the chamber leaving the bullet stuck in the lands. Makes a mess out of everything and will most likely DNF you for the match. Anneal after every firing and lightly brush the inside of the neck with a soft nylon brush. Do a ladder test with a chrono and pair your lowest ES with you best group then play with seating depth. You need to minimize vertical dispersion because it will kill you in a match especially at 1K.