Problems with bullet retention/neck tension

Sigogglin

Sigogglin

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I'm a noob, so I'm gonna ask some noob questions. The setup:

Lee 7.5x55 Swiss 3-die set, just using the FL sizing/decapping die and the seating die. Not putting any crimp on.
PPU 7.5x55 once fired brass, annealed before sizing.
Bullet: Hornady 150gr, .308 diameter. #3037.

The issue: I started noticing this when I was creating dummy rounds to try and find the proper seating depth for my K31. I.E., just start a bullet in the case, use the action of the rifle to chamber it, extract the round, and measure OAL. This is the procedure advised here, about 3/4 down the page: http://www.swissrifles.com/ammo/reload1.htm

I noticed that if the rim of the cartridge was in the cannelure of the bullet, then the bullet would "float" or "rattle" around. This was telling me (I think) that the neck tension was insufficient.

Measuring the neck diameter of a resized case the best I can with a caliper gives me an inside diameter of .308 on the nose, some cases might be .3078, some cases .3081. The bullet bearing surface measures just a shade under .308, like 3.078-3.079. Again, these measurements are taken with a caliper, as I do not have a micrometer.

The expander ball measures .3075-.3077, somewhere in that range.

If I remove the expander ball and just resize a case, the neck measures .295 or somewhere in that range.

What I'm reading other places suggests a neck tension in the .003 range, so after sizing, the neck *should* be .304-.305.

Does that track? Do you think the issue is with the dies or my process?
 
It sounds like the mandrel is oversized. Is it maybe larger than the bullet diameter? Might be an easy fix with a drill and some sandpaper or a fine file
 
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Catfish said:
It sounds like the mandrel is oversized. Is it maybe larger than the bullet diameter? Might be an easy fix with a drill and some sandpaper or a fine file
Click to expand...
Yeah, that looks like the issue. I have a spare mandrel/expander ball that's about .001 smaller, and it produces case necks in the .306 range, which is what my .30-06 RCBS die produces as well.

Given that I've had issues with both of the Lee die sets I own, I think they've made me into an RCBS man.
 
I’ve used a bunch of Lee die sets (over 20?) and only had a couple of problems, but one of them was an expander that was too large. Like @Catfish said, a little time in a drill with some sandpaper took care of it.

For bottleneck rifle, I have become a fan of the Redding bushing style sizing dies. Alternately, you could use the Lee sizing die, without the expander, and then follow up with a mandrel expander die.
 
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Another thought would be to try a different brand of brass. Brass can vary from one manufacturer to another.

And as for the expander ball, instead of a "drill & sandpaper" route,, a lathe would be the best route to take to assure you get the correct size necessary.
 
I agree with the above that your mandrel is large. You could call lee and see if the will send you a new mandrel. PPU brass is decent brass in 7.5x55. Norma is the only other current manufacturer that you can get in the states. I think you can get swiss match brass out of Canada. I use PPU in competition and won 2 bronze medal in cmp vintage match. However I had a few, like 3 out if 400 cases that split the neck on first firing.
 
You can order an under size ball. Although, I would just sand it down as suggested.
leeprecision.com

Custom Oversized Ez X Expander - Lee Precision

Custom Oversized Ez X Expander, for the Full Length Sizing die. Please specify how many thousandths you would like it oversized in the box below. Current lead time is around 4 weeks.
leeprecision.com leeprecision.com

Prvi Partizan Brass 7.5x55 Swiss Unprimed Bag of 50 - Graf & Sons

Imported from Serbia. Fully reloadable brass cases. Accept boxer primers. This is not loaded ammunition.
www.grafs.com www.grafs.com
 
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You are correct about -0.003" neck id per bullet diameter. I've never seen a bullet from a major mfg that was undersized so that's unlikely. Sounds like either the expander is oversized for the bullet being used, or the case isn't going into the die far enough. One other thing that comes to mind is case neck tension variations caused by work hardening, which is remedied by annealing. Do you have a case gauge to check the shoulder setback and trim length?
 
All your measurements sound like the expander ball is correct. One question is why did you anneal once fired? Was the brass really old and brittle? Maybe the brass has now become soft and lost some elasticity due to annealing. Was it sized before or after annealing?
 
Did the Lee dies come with two expanders? The only Lee die set that I have that came with two expanders was 7.62x39 - one was for 308 bullets, and the other was for 310 bullets.
 
Bringing this back up top. I'm going to start loading 7.5 Swiss and I bought Lee dies, but i haven't yet opened the box and can still return them. Should I just find Redding dies somewhere? I keep reading the non-redding sizing dies overwork the brass and only the Redding is made for the K31 chamber size. Given the cost of the loaded PPU ($1.25/ea) and unfired brass ($.70/ea) I'm not sure "overworking the brass" is something I want to play with since I'm not set up to anneal properly.
 
Redding and hornady dies are cut for the k31. I personally have hornady and a family member has the redding set. We both are happy with the dies for the k31. I run ppu brass, I have 4 or 5 firings on some but I've also had neck splits on first firing. That being said, I'm not sure how much more "over working" the brass other die sets are in comparison.
 
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I'm not finding a Hornady set. I've got a Redding set in my cart at Grafs.
What tools do you suggest for trimming 7.5 swiss. I can't find a pilot for my usual Lyman tool.
 

HORNADY 7.5MMx55 (K-31) SER. III FL 2-DIE SET, S/H #2 - Graf & Sons

Hornady Custom-Grade™ New Dimension™ Dies are the most advanced reloading dies available today. They’re created from select steel that’s heat-treated to ensure it’s got the durability needed for a lifetime of reloading. Custom-Grade New Dimension Dies are so well crafted, they’re guaranteed...
www.grafs.com www.grafs.com

Here is the hornady set. I use a rcbs trimmer. It takes a standard .30 cal pilot.
 
Too bad Redding doesn't make a bushing style sizing die for this cartridge. That would have been my advice.

Any standard (non-bushing) sizing die will probably over-work the brass, it is just the nature of the beast.

It would be possible to open up the neck area in the Lee die by honing it to the desired dimension, but then that die will only work for brass with a certain neck wall thickness.

I would suggest not using the expander mandrel in the sizing die. Instead, I would use a separate mandrel expander die. I feel this stresses the shoulder area of the brass less, which may help with longevity of the brass.
 
I've been using a Lyman trimmer with pilots that act as a stop so you don't trim too much. I think I'm just going to cut down a 30.06 pilot to the 2.18 inch trim length since Lyman doesn't have one available and I don't want to invest more on a new trimming set up.
 
Toprudder said:
Too bad Redding doesn't make a bushing style sizing die for this cartridge. That would have been my advice.

Any standard (non-bushing) sizing die will probably over-work the brass, it is just the nature of the beast.

It would be possible to open up the neck area in the Lee die by honing it to the desired dimension, but then that die will only work for brass with a certain neck wall thickness.

I would suggest not using the expander mandrel in the sizing die. Instead, I would use a separate mandrel expander die. I feel this stresses the shoulder area of the brass less, which may help with longevity of the brass.
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This may not be an issue. Only brass out there is PPU and Norma, and the Norma is like 2 bucks a case so realistically PPU is the only game in town.
S&B also has loaded 7.5 Swiss on the market but consensus is S&B brass sucks and PPU loaded costs exactly the same price as S&B.
 
beamernc said:
Tim, is that consensus just on the S&B 7.5 Swiss brass? S&B 6.8 SPC brass is the preferred brass for reloading.
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Seems to be among the few guys I asked at CRPC. They all prefer the PPU. They say the S&B brass is thin and brittle after the first firing.
 
@Timfoilhat Want to try out salt bath annealing? I have the stuff and hardly ever used it but I do have a couple batches of brass queued up.
 
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Catfish said:
@Timfoilhat Want to try out salt bath annealing? I have the stuff and hardly ever used it but I do have a couple batches of brass queued up.
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I'm not sure if I'm up to 900 degree molten salt without hurting myself or destroying something. How's high is the danger factor?
 
Less than lead casting because you don't pour anything. the setup is well contained. Risk is low but a burn would def. hurt.
 
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