Concentricity?

[newton]

Who here regularly checks the concentricity of their loaded rifle ammo? I just started noticing that when I have rounds that "seemed" not right, they shot not right. Go figure......

I don't have a fancy measuring device, but I made myself a thing that I can roll the ammo on and see if the boolit wobbles.

But as far as remedying it, for those of you who pay attention to such things, what did you do? I ordered some NOE expanders for my Lee Universal, I am hoping this helps more than just flaring the mouth itself. I seat with a Hornady die with the floating stem, but have read that its not near as accurate as people think because it only aligns the case mouth at best. I really am not sure if buying a Forseter or Redding benchrest die is going to help that much - or does it?

[pmer]

I used the micrometer seating dies for High Power shooting. If I had ammo with more than .003 run out i would use it for practice and the ones with the least run out for the farthest targets. Do you have another seating die just try?

[newton]

No other seating die. I really think that my issue is during the sizing operation with the expander pulling up through the neck. I am going to try removing it and just using the NOE expanders to open the neck back up after sizing.

[country gent]

This can start with the sizing die and brass and multiply from there with each operation. You didnt say what round you are loading so Have to be general. I have checked runout both cases and loaded rounds. Start checking your cases for case thickness run out. Cases that are off can become bowed or bannana shaped during sizing. Thru cross sectioning cases I have fopund that a case with neck wall variations in the neck of .001 side to side will get worse to the head of the case. A bowed case is out from the get go. Out of spec necks dont expand or bell evenly leading to more error. Seating bullets into these necks increases it again as the necks tension isnt even around. Dies that arnt true can also make out of round ammo. Sometimes a rubber o ring under the lock rings allow the die to float and center up helping concentricity. A good fit between bullet and seater can also help. The bowed effect can be more pronounced on longer cases. I made a gages up to check run out, neck wall thickness at case neck and back close to case head. The runout gage is simple 2 bars with 1/2" gage balls the one mount is adjustable for case length. there is a stop for case head to set against. And a .0001 finger indicator adjustable to read the bullets runout. In use the round is set into the V formed by the gage balls and pulled against the stop, then slowly spun reading the indicators runout. CAse thickness can be measured at the neck with a ball mike or gages sold for this. The gage for checking just ahead of case head is pretty involved. You can section a case and check it with ball mics but its destructive measuring as the case will no longer be useable. Another cause can be burrs or dented case mouths.

[noisewaterphd]

Always for rifle cartridges. It definitely seems to make a difference for me.

I use FL bushing dies (no expander) and turn the necks, or Lee collet dies in the calibers they have available.

For cast I then use expander die prior to seating, and taper crimp just to remove the flare.

Proper seating plug can make a big difference, I prefer Forester ultra micrometer seating dies with great success.

The expander ball is also a major problem for me, never use them. In addition to concentricity they also have a tendency to screw up the shoulder bump.

[newton]

Speaking of forester dies, do they allow seating of cast boolits? I am loading the .223 and sizing to .2255"

[noisewaterphd]

Speaking of forester dies, do they allow seating of cast boolits? I am loading the .223 and sizing to .2255"

It really just depends on the bullet profile, sometimes the stock plug is a great fit, sometimes it is not.

If it is not a good fit for your bullet, Forester will make you a plug that does. Actually, I'm pretty sure most companies will make you a seating plug for their dies.

...And, I do not have the Forester in .223

Wish I could be more help. If I had to guess, I'd bet that Forester's seating plug for the .223, by default, is built to fit 55-75gr tangent ogive jacketed bullets.

[ascast]

yes, always for rifle. Anything over 0.003" R.O. gets pulled or used for plinking. Assuming your bullets are round, it's in the cases as stated above.
It's worth a mention that seating speed can cause problems. A nice slow,even hand on the seating stroke helps. A bit of lube on the bullet nose helps too. Ultimately your into fine tuning your brass. You might try the concentricity gage on re-sized cases. Anything that shows up here can be set aside for later solution.