Help, concentricity problems.

[Chawlston]

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How well would a floating expander from redding work? Would they help solve the problem? They have them in just about every cal.

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You would still have the alignment issue but it could help some. It is much easier to just seek the permanent solution. Turn the necks and remove the expander ball and be done with it.

James

 

[Chawlston]

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I think I actually tried the partial fl sizing by accident. After 1-2 full near max loads with my 300 wby (resizing with a lee collet die) I found the bolt had slight tension while closing. I decided to experiment with that phenominon compared to fl sizing by just bumping the shoulder back about .001-.002" inches. After hunting in crappy conditions in Alaska I decided that I would not hunt with ammo that didn't have a bit of room for dust, rain and snow. (Plus we get snow and ice here in Wisconsin.). Anyhow what I found in my rifle was that the ammo that had bolt tension to close went about 3" left of the ammo that had been sized with .001-.002 room. I actually wound up with 2 distinct groups and no discernable difference in accuracy. I'll admit I didn't do alot of testing but I was really surprised at the result. Being I don't want to hunt with PFL ammo I gave up on the concept as being one that would work for my hunting conditions. I know some people seem to like it. It just doesn't seem like a good way to prep ammo for hunting especially where dangerous game or follow up shots for the hunt of a lifetime might be involved.
After all this I think I've come to the conclusion that there are trade off's in ammo prepping. One might give a slight edge in accuracy....one will probably be more reliable in the field.

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Ammo that flops around in the chamber with the bullet oriented anywhere but striaght down the barrel will not get the job done at the ranges we shoot. You can use it for close shots, but for longer range, you will get significant shot dispersal. You probably will not benefit from the technques we have discussed here if you allow your rounds to flop in the chamber. Finally, ammo that fits the chamber is not less realiable, it is more realiable.

James

 

[Chawlston]

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Once you fire the brass one time it takes the basic dimensions of the chamber (hence fireform). Take advantage of the close dimensions and just partial size it so that it gets the compression mentioned earlier when a round is chambered.... You will be pleased with the results.

James

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Great discussion kraky and Chawlston.

The thing I'm not sure about is the amount of compression you will get between the case-head/bolt-face and the case-shoulder/chamber-shoulder after only one firing. I took the following measurements with a Stoney Point Head and Shoulders Gauge on cases fired from a Steyr 30-06 going from new cases to the 4th firing:

new cases - 4.0400" (the measurement doesn't mean much, just it's relationship to the other measurements)
once fired - 4.0485"
twice fired - 4.0500"
3 times fired - 4.0510"
4 times fired - 4.0515"

These were neck sized with the Lee Collet and after the 4th firing the cases became hard to chamber and had to be PFLR'ed back to 4.0510" to a slight crush fit.

The point is that after the first firing the shoulder was still .003" from a crush fit. I did a test with some loads that were loaded at the same time and found that PFLR'ed loads with the shoulder moved back to a slight crush fit and crimped with the Lee Factory Crimp gave the best results.

Next is to PFLR once fired cases and see if the body sizing moves the shoulder far enough forward (which I can then push back to the proper place) to get a crush fit on once fired brass.

I'm with you Chawlston in that expander buttons are a long ago bad memory. For me it is the Lee Collet Neck Sizer and Redding Body Dies.

When is the best time to turn necks, on new cases or after the first firing?

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To get full case expansion, you may have to up the powder charge or tighten the neck tension to get some additional pressure to fully expand cases.

A little WD40 applied to the fingers and then wiped on the case to create just a light film will aid in full case expansion.

It is best to turn necks on vigin brass. But you can do it after one firing if you get the inside the neck clean. Virgin brass helps here.

James

 

[AJ Peacock]

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All,

I've been reloading (clean, deprime, prime, powder seat) for 30 years. All my rifles will shoot sub-MOA.

My problem is that until recently, I just worked up a load, reloaded (sorted brass by weight), weighed each charge and called it good.

Since I ordered a 338AM from Kirby, I decided I needed to be able to measure things like bearing surface length on my bullets (so I got some stoney points gauges), Concentricity (so I bought a Sinclair gauge) etc.

Well, I grabbed my box of Norma 7RM brass (mostly once fired, some still virgin, some loaded) and started checking the concentricity.

WHOA!! measured just in front of the neck, the loaded rounds run from .0015 - .008 runout. The once fired measured on the neck runout .002-005" and the new virgin cases run .002-.004" runout.

I immediately measured some of my .243 winchester rounds same type of resolts, then the 7mm-08 same thing, then some factory Remington 7RM, it measured .002-.006" runout

On the .243, I use Pacific neck size dies, on the 7RM I use Forster Neck die, on the 7mm-08 I use RCBS full length.

I polished the expander button on the 7RM Forster neck die, and resized some of the brass; no real change before-after on case neck runout sometimes .001 better sometime .001 worse.

I'm not setup to measure neck thickness.

Since its pretty much the same on 3 different calibers and the factory ammo, do I have a problem? The runout numbers above are extreme spread on the dial indicator. I read that .002" was an allowable limit for runout with bench guns etc. These are all factory chambers with nothing done to the brass but trim/chamfer flash hole debur.

I'm using the same Rock Chucker single stage press I've been using for 30 years.

I now understand the saying "ignorance is bliss".

Any ideas are appreciated.

Thanks,
Don

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Well, I'm happy now. My concentricity problems were solved with a "get back to basics" approach.

I read the Zediker book "Handloading for Competition" and took all his advice with regard to setting up my dies etc.

Here is the step by step I followed to resolve my 7RM concentricity problems.

I purchased a neck thickness mic from sinclair, as well as the mandrels for using my sinclair neck turner for the 7mm.

1) Removed the shellholder spring from the presses.
2) Polished the expander button on my FL size die and cleaned the die.
3) 'Tuned' the decapper assembly to center in the FL die.
4) Measured everything on my once fired Norma brass (head to shoulder, neck thickness etc.) and wrote it all down.
5) Sized all the brass, noting its orientation in the die.
6) Neck turned all the brass to .0145" thickness. This brass was very consistent. Typically only .001" or less variance. .0145" just barely cleaned most of it back to a variance of nil.
7) Sized all the brass again, orienting the brass 180degrees different than the first time. (checked Runout, all but 2 were under .001" runout measured halfway up case neck)
8) Primed, Powder
9) Seated using an old RCBS Mic seating die to within .002" of the lands. This die does not guide the case with a spring bushing. Runouts increased at this step by around .0008". This resulted in an average runout measured on the bullet of .001505" for the 20 rounds I loaded.

I believe I can improve the seating die runout problem by purchasing a good Forster seating die with the sliding case support.

I also believe my old RCBS shellholder is not 100% true, it was leaving flats inside the rims of the cases. So I think I'll get a 'competition' shellholder and see if that helps.

One additional thing that the book recommended, was to use Imperial sizing wax. I agree with Zediker, that this wax does a more consistent job than anything I have used before (I was using the spray on lubricant).

Thats it, the 20 cases I loaded are for a ladder test with the 162gr A-max and IMR4350.

I'll update this thread after I perform the test.

Don