Correcting runout after the fact

[tlk]

So I see some processes and tools on how to straighten up the runout on a loaded and round and I have a question: If you correct this, dont you do two things: 1) oval the case mouth and 2) oval/pooch the neck to one side at the lowest point the bullet comes in contact with the case? Wouldn't this affect accuracy "worser" than just leaving it alone? Seems to me that in order to true up a round to have zero rounout with this method you would end up bending portions of the case.

I need more light.

 

[flashhole]

Hope you don't mind if I camp onto this thread. I want to see the responses. My personal opinion is you get better bang for the buck finding and eliminating the process problems that result in runout than you get trying to correct it after the fact.

 

[Mikecr]

The only way to straighten brass is by firing it in your chamber.
When this isn't enough, toss it. Prevent the runout with it's replacement..

 

[tlk]

Mike, I am with you on this. Methinks it is snake oil, for the reasons I posted. I see this process and the new tools advertised for making factory and handloads runout free. I aint buying the reasoning.

If I have ANY ammo loaded on brass that can have up to .003 variation in neck thickness an a single case (WW) , how can warping the neck by pressing on the bullet help?

For neck turned brass, I am still suspicious. If I am wrong please let me know.

 

[J E Custom]

I am in the process of testing this problem and intend to load at least 50 rounds and
then sorting by the amount of run out. then testing loads that are over .002 and straightening
the ones that are .003 down to .002 and comparing them to loads that were .002 with no
straitening and then comparing the ones that were under .001 to some that were straightened
to less that .001 and also try to test the ones that are over .004 after they are straightened
and see if there is any advantage in straightening at all.

I know that sorting by concentricity improves the SDs and hence the accuracy I just don't know
how much you can straighten a case before it hurts SDs and accuracy. That's why I want to do
real test with enough data to satisfy me at least.

I will post my results as soon as I have it. (It will be unbiased because I have no opinion or
hidden agenda ) and just want to know for my self if it is a worthwhile process to improve
My loads.

Al shots will be through a 35 p chronograph and will be well documented in SDs,Velocity and
accuracy in like barrel conditions,Temp, clean and stable conditions.

J E CUSTOM

 

[kraky]

I just got the hornady checker/fixer tool. Not sure what to make of it. It barely shows runnout with most of my ammo. My rcbs v-block can show .006 and the hornady might show .001. Sometimes I fix it on my hornady and it actually gets worse checking on the rcbs. It's almost like the 2 units pick up concentricity in different areas. I'm quite sure the hornady might have a problem because it is measureing too close to the support near the tip of the bullet.

ALL THIS BRINGS MY QUESTION FOR YOU GURUS. Exactly how is the case supported in a chamber?? Does it kind of just lie there on the bottom....or....if you have tighter headspace tolerance....say .002 head space does the case actually lift up from the chamber slightly being supported at the base of the case and then at the shoulder?? If that's the way it is then the hornady tool should probably suffice.

 

[kraky]

BTW----very interested in your outcome J E Custom!! Thanks for your efforts.

 

[Gene]

Concentricity begins in the sizing die. Dies with expander buttons are a frequent problem. Bushing dies usually result in straighter necks. If the neck is out of round, the bullet cannot begin its flight in a straight line thru the throat. I am not familiar with the Hornady, but I did own a Bersin and sold it. What this tool does is force the bullet slightly against the low side, in effect, bending the neck. Yes, after that case is fired, the neck should straighten out to fit the chamber.

The seater die can also cause the problem, if the bullet tip plug does not fit properly, or the case does not move upward thru the die in a straight line. Zero concentricity is near impossible to achieve. I am satisfied with .003-.004" runout. I agree with sorting by concentricity, as long as each shot is indexed to keep the same high side in identical position.

 

[Mikecr]

Ya'll just missed a big discussion about this:
http://www.longrangehunting.com/forums/f28/concentricity-how-much-52677/