Reading a sinclair concentricity gauge

[bigedp51]

Why It's Smart to Full-Length Size Your Brass
Commentary by Erik Cortina Team Lapua USA



Below click on image below to enlarge.

 

[GW Hunter]

For the record I full length size... but, to each his own with this topic is how I feel about it though.

Regarding resized cases that have neck runout due to whatever reason... Is fire forming them the only way to get them straight again?

 

[Mikecr]

Regarding resized cases that have neck runout due to whatever reason... Is fire forming them the only way to get them straight again?

Yes. Your chamber is your best die, hammering all thickness variance inward.

On the 'perfect fit', it's just that, and should be a load developed condition and managed as consistent. This is viable only with an actual plan for it.

 

[bigedp51]

For the record I full length size... but, to each his own with this topic is how I feel about it though.

Regarding resized cases that have neck runout due to whatever reason... Is fire forming them the only way to get them straight again?

You stated above you full length resize, and if you remove the expander and size your cases they will be as straight and concentric as they ever will be. If you size the case with the expander in the die the neck thickness variations will be forced to the outside of the case neck. Meaning as long as you do not neck turn you will always read the neck thickness variations when measuring case neck runout.

The military considers match grade ammunition to have .003 or less "bullet" runout. Your new runout gauge will let you know how much runout you have. And you will need to find out "what" is causing the runout, meaning is it the case, the sizing operation or bullet seating.

And again if you have the Redding neck thickness gauge it will tell you a great deal about the quality of the cases. And you could sort you cases with the least neck thickness variations and not have to turn the necks. Neck turning can create its own problems with donuts as the brass flows upward into the case neck. And if you have a off the shelf factory rifle many of the brass prep benchrest shooter do will have no effect on your rifle for hunting.

 

[redleg1013]

Just for the record, Redding is not the only game in town for a "neck checker". Hornady and Sinclair both sell their versions at a lower price point, K&M sells one, but it attaches to their turner if I remember correctly, measures while/after turning. Or, if you're so inclined, build one, and slap a tenths indicator on it.

 

[GW Hunter]

I'm about to lose the expander ball... I replaced the stock expander on my Redding S type bushing die with the carbide one a while back. There was a noticeable difference in the resistance of the stroke of the ram during resizing. I think I'm ready to remove it all together... The Redding gauge is the one i've had my eye on. Looks pretty painless to use.

 

[bigedp51]

Don't be overly disappointed with your runout readings with your Redding bushing die with a factory rifle. When you reduce the neck diameter .004 or more with a bushing die you can induce neck runout. And this is covered in the Redding bushing die FAQ along with when to use the expander in their die if you do not neck turn.

The reason so many reloaders use a body die and the Lee collet neck sizing die is because it produces "less" runout than a bushing die in a factory rifle.

Bushing dies work best with custom tight neck chambers and neck turned brass. And I can tell you my Forster full length dies produce less runout than any bushing die I have. And this is because of the amount the neck must be reduced in diameter in factory chambers.

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

Tech Line & Tips (FAQs)
Concentricity & Bushing Dies
https://www.redding-reloading.com/tech-line-a-tips-faqs/142-concentricity-a-bushing-dies
We have conducted many tests over the years on the various factors contributing to concentricity problems with bottleneck cases. We have repeatedly found a definite correlation between the uniformity of the brass (or lack of it) and the resulting concentricity of the neck to the body of the case.

An interesting experiment also revealed that neck turning of brass that was intentionally sorted as non-uniform, showed little or no concentricity improvement when used in standard S.A.A.M.I. spec chambers. Conversely brass that was sorted and selected for uniformity remained uniform and concentric with or without a neck turning operation.

Tech Line & Tips (FAQs)
Some Frequently Asked Questions
https://www.redding-reloading.com/tech-line-a-tips-faqs/132-faqs1

Question: Do I need to use the expander button that came with my Type "S" Die?

Answer: It is advisable to use an expander button to maintain consistent neck tension if the case necks have not been turned to a uniform wall thickness. However, the expander button can be replaced with the Decapping Pin Retainer (included with your Type "S" Die) if the user does not wish to use an expander button. If the neck wall thickness varies more than 0.002", it may be necessary to use a bushing a couple of thousandths smaller than your calculations indicate, and then use a size button in the die to determine the final inside neck diameter.