neck tension

[Tom Thomson]

I think that I just learned something but I'm not sure what. I have been using .010 tension (RCBS) size die on 308. That seemed to be too much so I ordered and just received a Redding S with a .337 bushing for .002 tension. With no other changes, the group went all to hell and dropped abt 1". Savage 110 - Hornaday FMJ/BT 150 gr - 12 gr Trailboss - col at the lands. What happened???
tommyt

 

[spclark]

I load 155.5 Berger Fullbores for Palma with 0.0015" neck tension, 0.020" off the lands. Clocked at 3,050 fps for score shooting out to 1,000 yards, my take on your question is that with such a drastic change in neck tension you'll need to re-tune your load. May be seating depth, may be charge weight, may be powder / primer choice... may be a little or a lot of all four in some combo.

If I tried to load 0.010" neck tension I'd be seeing jacket metal shavings on my benchtop for sure.

 

[LHSmith]

Using bushing dies is adds another parameter to tuning loads. First, did you allow the bushing to float...by not tightening the top knurled stem to the die? Second, I doubt you had 0.010 neck tension from previous dies. Adjust your load by changing seat depth and then by powder charge. It is usually best to buy 3 bushings, one smaller and one larger than the one you have now.
You said "group went to h-" ........I would never draw any conclusion from firing just one group.

 

[Tom Thomson]

LH
Yes, the bushing was floated - just like Redding says. Yes, the tension was .010 - measuring the sized case and the loaded case (Brown & Sharpe 1" micrometer). No, I would not judge by one group - 4 groups of 5 all acted the same.
tommyt

 

[LHSmith]

I just sized an no turn .308 RP case in a RCBS .308 FL die, seated a 168 gr. Sierra and got 0.0022 difference between the sized case and loaded case. Are you tumbling brass in stn.stl. pins?

 

[Dusty Stevens]

You must have had a big handle to seat bullets with .010 tension!

 

[Tom Thomson]

LH
Negatory on the stainless pins - I use corncob in a vibrator bowl. The difference in measurements may be the fact that I don't use the sizing plug. To me it makes no sense to squeeze the brass way down then swell it back out. If you check a case out of the die without the sizing plug, I'll bet our numbers will be closer.
GSTAY
No, I don't have a chrono so I really don't know, but it stands to reason that if the "group" dropped an inch it must be due to lower MV. The question is, why would a looser fit on the bullet cause this? It looks as though the reverse would be true.
tommyt

 

[LHSmith]

LH
To me it makes no sense to squeeze the brass way down then swell it back out.

You are still expanding the neck when inserting the BT bullet....only your method, I would think, would give horrific loaded cartridge run-out.....inserting copper into brass creates more friction/galling than inserting brass into lubed polished steel.

 

[LHSmith]

LH
The question is, why would a looser fit on the bullet cause this? It looks as though the reverse would be true.

Light neck tension will allow the bullet to release sooner before peak pressure is achieved.

 

[/VH]

Tom,

Another thing to consider; when you were seating into the RCBS sized cases, did your seater stem leave a mark on your bullets? If not, the tip of the bullet may be bottoming out in the stem.

 

[fguffey]

Light neck tension will allow the bullet to release sooner before peak pressure is achieved.

I do not have neck tension, I have bullet hold. I do not have a gage that reads tension, I have gages that measure in hold and interference fit. I am the fan of bullet hold, I want all the bullet hold I can get. difference?

Who knows? The difference between bullet hold and a case with a loose neck could be 40 pounds, when we pull the trigger how long does it take for the pressure to go from 10 pounds psi to 40 pounds PSI? Then there is the expansion of the case neck, who knows how many pounds of pressure is required to expand the neck of the case?

I am the fan of bullet hold. I would be a neck tension fan if I could find a gage that measured in tensions. I have tensions gages, my tension gages measure in pounds and deflection.

F. Guffey

 

[Ggmac]

12 gr of trail boss ? We're you fireforming ? The 150 gr bullets with 12 gr at 100 ?
Help me understand , I'm sure I'm missing something .
Gary

 

[mikecr]

To me it makes no sense to squeeze the brass way down then swell it back out.

You're right, it makes no sense to squeeze the brass way down..

 

[bigedp51]

Tom Thomson

Is your Savage .308 a stock off the shelf factory rifle with a SAAMI chamber?

A standard full length non-bushing die needs the expander to expand the neck to the proper inside neck diameter. The expander also pushes/forces any neck irregularities to the outside of the neck.

If you are not neck turning your brass with your new bushing die your are just pushing any neck irregularities to the inside of the neck.

With a standard factory rifle and chamber if you are sizing the case neck over .005 at one time with a bushing die it can cause a increase in neck runout.

I would use a Forster full length die with its high mounted expander on any stock factory rifle and forget bushing dies.

If you do not have a neck thickness gauge and a runout gauge you will be better off with a standard full length die like the Forster and forget bushing dies.

Neck Tension, Bushing Dies and Other Reloading Mysteries
by Germán A. Salazar
http://riflemansjournal.blogspot.com/2009/10/reloading-neck-tension.html

Two-Step Sizing and Case Neck Concentricity
by: Germán A. Salazar
http://riflemansjournal.blogspot.com/2010/04/reloading-two-step-sizing-and.html

FL Bushing Dies vs. Honed FL Dies
http://www.accurateshooter.com/technical-articles/reloading/fl-bushing-dies-vs-honed-fl-dies/

 

[bigedp51]

12 gr of trail boss ? We're you fireforming ? The 150 gr bullets with 12 gr at 100 ?
Help me understand , I'm sure I'm missing something .
Gary

Below fireforming .303 British cases and a great plinking load with Trail Boss. And your brass can't stretch and thin in the base web area when the pressure is kept low. And the best part is Trail Boss makes the Enfield's brass butt plate "softer" when firing 100 to 200 rounds.

 

[Ggmac]

Thanks , big Ed .

 

[bigedp51]

Thanks , big Ed .

I'm waiting for Tom Thomson the OP to get home from work and answer a few questions, like what made him take the expander out of his die in the first place?

 

[Tom Thomson]

Gg
just a plinker load, but I know I can get better accuracy than I am seeing so far.
tommyt

 

[bigedp51]

Gg
just a plinker load, but I know I can get better accuracy than I am seeing so far.
tommyt

I asked you a few questions in post #16, if you want some help we need answers, beginning with what is the diameter of your fired necks. Meaning how much are you reducing the neck diameter with your .337 bushing?

Does your Savage rifle have a standard SAAMI chamber?

Are you neck turning?

And what gauges do you have?

 

[Tom Thomson]

biged
what's an op?
tommyt