6.5 x 47 lapua Split Necks

[JohnT]

Hi there,

have just started load development with the 6.5 x 47L, Sav Short Action, Shilen Ractchet Barrel 1:8" 28" long. Its a no turn neck and I had it throated for Berger 130VLD's but am using mainly 123gr Sierras or 120gr A-Max. Arrived at a load of 38.1gr RL15 with CC400 for the 120gr. On my 4th Firing I had quite a few split necks. The brass was FLS each time with a Forster Benchrest die with 0.001" pushback at the shoulder. Brass was not annealed from new.

Very surprised since I had heard about how good & strong Lapua Brass is. Here are some dimensions taken with a micrometer:

New Brass Neck Diameter: 0.2879"
Loaded Round: 0.2908"
Fired Case: 0.2957"

Has anyone had this issue before? Have I just got a bad batch of brass. Are any of my dimensions above out of wack?

Would appreciate your advice as to what is most likely causing this as I am new to this calibre.

Regards,
JohnT

 

[DJ111]

I would think you are over working your brass? Pull the expander ball out of your die and see how small your neck diameter is after sizing without the expander ball. I would bet it is sizing it down to around .286 or less and if your fired cases are ending up at .295+ that is a lot of sizing every time.

I use a Type S FL die with a .287 bushing with lightly turned necks and end up with a .289 loaded round with about .0001 neck tension. I have a .292 chamber and my fired cases end up at .2905

I have over 9 (HOT) firings on some cases and have no issues with necks.

This is not the answer you want to hear but I bet it is in the right direction you need to look.

It also looks like you might have donuts forming at the base of your neck?

Hope this helps,
Dallas

 

[camac]

Dallas sounds spot on. Most "off the shelf" sizers are made for the thinnest of possible brass so on normal bras squeeze in too far and out again. The good thing for you John is Forster can hone out the neck to your correct neck tension very cheaply - contact them. With new Lapua brass you will probably want around a .290- 291 neck but send them a couple of shells and/or measurements of loaded round.

Of course annealing also helps.

 

[camac]

It also looks like you might have donuts forming at the base of your neck?

Hope this helps,
Dallas

Possibly donuts on bottom but may also be FL die not touching bottom of neck so still represents fired chamber size.

 

[JohnT]

Thanks guys, Also found that the Forster die was badly scratching the brass and so was the expander ball. Polished both the ball and the neck of die with some green jewellers rouge. Better now especially the expander ball ( It had 2 rings of brass where it was gouging the case necks) but even now still visibly scratches the necks. Being in Australia the postage costs sending stuff to USA becomes prohibitive so I have ordered some Redding type S dies from Grafs with ti coated bushings in 0.289 & 0.290. I think you can see the scratches in the photo but not sure if this would be enough to overwork the case or deep enough to promote splitting.

I asked for a no turn neck so it looks like the neck may be 0.296 or 7; maybe a bit too generous. But on reviewing the data maybe 38.1gr of RL 15 may be a bit stiff as well (with 120 A-Max & CCI400) so will back off and see how I go. Just that it seemed to want to go higher for accuracy.

Thanks everyone for your excellent analysis.

regards
JohnT

 

[JohnT]

DJ actually checked and a 6.5mm bullet just falls through the neck so no donuts. But perhaps the neck part of my chamber is a mite generous.

The Forster dies without button sizes the case to 0.2858" and with the button expands to 0.2872. The fired dimension being approx 0.295 there is 10 thou movement. Probably too much.

regards
JohnT