Neck tension vs Concentricity

[Dusty Stevens]

I know it's not my thread, but if you don't mind, what do you consider "a lot" of eccentricity?

Id say .003-.005 you need to start getting ready to change something- then you can get it down to the zero you deserve

 

[cw308]

Neck tension will be different if your not neck turning . Brass is thicker from brand to brand .Size your case , measures the outer diameter , measure the neck thickness and the bullet diameter . As a example a 308 case sized , the OD of the neck .336 , case neck thickness .012 measured at the 12 & 6 o'clock position = .024 . 308 bullet OD is .308 The seated bullet in the case OD measurement measures .338 , your neck tension is .002
If your case neck thickness is thicker or thinner your tension will be different. Did I see any difference shooting 200 yards , No . Stopped using the bushing dies went back to a bushingless F/L RCBS die , nothing fancy worked fine for me and my runout is .001 on the average.

 

[johara1]

I know it's not my thread, but if you don't mind, what do you consider "a lot" of eccentricity?

.001, that would be a total of .002 .... jim

 

[Milo 2.0]

I know it's not my thread, but if you don't mind, what do you consider "a lot" of eccentricity?

I must be on the same page, most are missing it. I believe, if your wife thinks you are a pussy, you've went too far, lmao

 

[JimSC]

The OP brings up a good point about how much does it matter if your shooting form and wind/mirage calls are off. I shot some 300 yard groups last week at a unfamiliar range. On the first two 20 shot groups the vertical height was horrible at just over 1.5 MOA and a 95% CEP of 1.4, the second group got a little better with a vertical of 1 MOA and a 95% CEP of a little less than a MOA. By the third group I was feeling more comfortable behind the gun and had a group with a vertical of .7 with 19 of the 20 shots lined up in a .3 MOA tall by 1.5 MOA long ribbon which was off center and a bit below below the waterline.

My point is the were prepped and loaded the same way, but on my first two it was all shooter error on the vertical. A random dozen were checked out of 100 total were checked for concentricity, and all dozen were below .001. My case prep is fancier than some folks and way more simple than others here but but all I do to the cases are wet tumble, anneal every reload, keep the case length within .005, and full length resize using a Redding S bushing. That's all that is needed for me at least to get my groups verticals below .5 MOA, mileage may vary for others. My big challenge now is wind/mirage calling. I know the theory now I need to start practicing it.

BTW I think the OP nailed it with no matter how good your equipment and form is if you aren't reading the wind/mirage right then your scores are going to be in the toilet regardless

 

[ngb1787]

Unless you got a lot of eccentricity dont worry about it. Once you get good dies and prove them your concentricity checker will gather dust

Amen!

 

[ngb1787]

Still believe turning necks are very important,

 

[Falfan2017]

Id say .003-.005 you need to start getting ready to change something- then you can get it down to the zero you deserve

Where are you measuring? On the ogive or closer to the tip or shortly past the brass?

 

[Uncle Ed]

The Military considers match grade ammunition to have .003 or less bullet runout.

And I just read that David Tubb uses .004 neck tension in his long range loads.

 

[Dusty Stevens]

The Military considers match grade ammunition to have .003 or less bullet runout.
.

So that would mean about half that is marginal?

 

[Dusty Stevens]

Where are you measuring? On the ogive or closer to the tip or shortly past the brass?

What matters most is where the ogive contacts the rifling but like i said before, get a good sizing die and you wont even need to measure it anymore. You can check it in a few places to see whats going on

 

[Uncle Ed]

So that would mean about half that is marginal?

If the military considers .003 or less runout to be match grade ammunition, how could .0015 runout be marginal.

Or did you mean something else.

My question when I first read this was is this for iron sights or a scoped rifle or both.

And below many reloaders use the Lyman type "M" expander for their AR15 rifles. And this is .003 neck tension and bumping the case mouth onto the .226 part of the expander to aid straight inline bullet seating. And then use a taper crimp to reduce the case mouth diameter.

 

[Papa Charlie]

Good information here. But one question. Do you strive for minimum neck tension 0.0015"-0.002", or do you play with different tensions to get different group outcomes?

 

[Dusty Stevens]

If the military considers .003 or less runout to be match grade ammunition, how could .0015 runout be marginal.

Or did you mean something else.

My question when I first read this was is this for iron sights or a scoped rifle or both.

And below many reloaders use the Lyman type "M" expander for their AR15 rifles. And this is .003 neck tension and bumping the case mouth onto the .226 part of the expander to aid straight inline bullet seating. And then use a taper crimp to reduce the case mouth diameter.

I was saying not many on here consider military match grade to be much of a baseline for true match grade

 

[Dusty Stevens]

Good information here. But one question. Do you strive for minimum neck tension 0.0015"-0.002", or do you play with different tensions to get different group outcomes?

Gotta experiment

 

[JimSC]

And I just read that David Tubb uses .004 neck tension in his long range loads.

After reading the neck tension section in Litz's Modern Advancements Vol II he had some good results with three. That is what I use now and results are acceptable. My ammo can out shoot my abilities on most days

 

[Uncle Ed]

I was saying not many on here consider military match grade to be much of a baseline for true match grade

This is true, but in this forum you have benchrest shooters with custom rifles and reloaders with off the shelf factory rifles.

You have neck sizers, full length resizers and a full spectrum of type reloaders here.

And we even have reloaders with magic feeler gauges who invented the datum.

So do not forget many people come here to improve their reloads and do not shoot in competition.

 

[Dusty Stevens]

This is true, but in this forum you have benchrest shooters with custom rifles and reloaders with off the shelf factory rifles.

You have neck sizers, full length resizers and a full spectrum of type reloaders here.

And we even have reloaders with magic feeler gauges who invented the datum.

So do not forget many people come here to improve their reloads and do not shoot in competition.

You are so very correct sir.

 

[Schandler]

I am one of those fellas and use Forster coax for 6br. I “ feel” the neck tension when pushing bullet in case and sort by feel. Turn necks to clean up and Rifle shoots great but not one small hole and i like the idea of a gauge to measure pressure when seating and have always wanted to ask does such a tool exist for Forster ?? One day i will play with 6 ppc and have all the good toys even if it’s just for bragging rights but until then is there a gauge for seating pressure without using arbor press ?

 

[Puzzaz01]

I am one of those fellas and use Forster coax for 6br. I “ feel” the neck tension when pushing bullet in case and sort by feel. Turn necks to clean up and Rifle shoots great but not one small hole and i like the idea of a gauge to measure pressure when seating and have always wanted to ask does such a tool exist for Forster ?? One day i will play with 6 ppc and have all the good toys even if it’s just for bragging rights but until then is there a gauge for seating pressure without using arbor press ?

I believe I have read about a strain gauge that was electric and it was on a rock chucker. This was a few years back and if I remember correctly the price was more than a 21st century hydro press, just didn't believe it could do what I needed reliably.

Darrin