NECK TENSION

[shoot1]

Using Rcbs Gold Medal FL Bushing die and Seating die. The question is for all bushing dies that use an expander ball i.e.. .307 for 30 cal.. You can adjust bushing for thickness of case neck wall (.013 vs. .015 ). Then to increase neck tension in .0005 increments ,the only way possible to increase neck tension would be to polish the expander ball to a reduced size of .306.The bushing is sized accordingly. That should give .002 neck size reduction plus .001 of case metal memory maybe , for a total of .003. Divide that in half and neck tension should be .0015. Is my analysis correct.? I do shoot moly coated bullets. Or do you not worry about neck tension and do a moderate crimp? Control of concentricity is important. Your thoughts and experience please.

 

[DGW1949]

Your math seems correct. Spring back might vary from case to case.....but...
bear in mind that all .308 bullets aint actualy .308 .
Many (if not most) are measurably smaller.....and I've checked some that were as small as .3065 , which would make a .307 expander rather useless.....just sayin'.
First thing I'd do is put a Mic on the bullets that I was planning on using.
You may find that you'll end up keeping more than one size expander on hand.

Are you building service loads, hunting loads, or match loads?
I ask that because match bullets don't have a crimp groove, nor do all hunting bullets. To me, the lack of a crimp groove makes neck tension even more important.
Being's how the expander ball does the controlling, it is what you should center your attention on IF you are not getting satisfactory "bullet pull" with whatever brass you are using. You can turn down the OD of the neck later if it proves neccessary...which I doubt. I say that because I've used a lot of RCBS dies to load for a lot of .30-cal rifles and have yet to have a "tension" problem that wasn't tracable back to a specific bullet, or a round that wouldn't chamber.

DGW

 

[shoot1]

Thanks for your info! I Ioad for an M1 Garand and 03-A3 which I got new in the 60's and did the NRA style sporterization. I shoot targets with both and the A3 also hunts. Also shoot a 308 win. and 7 mm Rem Mag, both also hunt and shoot target.Like to shoot targets out to 600 yards but find most hunting shots are in the 125-300 yrds. range. Load hunting and some match bullets. My loads are focused on accuracy because the reduction in velocity is easily compensated for with your scope. It's just simple math.
Measuring seems to to be the my weak link . Using Lyman digital calipers which have been very close to the C mics I've tested. All are rated at +/- .001. Any suggestions on brand and model ?
All bullets are weighed and measured, and grouped.
Just finished polishing 2 expander balls to .306 and .305,will pair them up with bullets and a bushing. Is there a way to measure neck tension without getting exotic tools? all of my new brass is Lapua (308) Norma (30-06) and Nosler (7mm Rem Mag), fired brass is Rem. Win. and Fed. Have had supply problems with powder ,primers ,brass and specific bullets. Always looking for suppliers other than the big guys.
My goal is to produce loads witch are accurate and duplicate again. Thanks Shoot 1