concentricity issues

[hhunter23]

ive been reloading for about 10 years (mostly for 270, now a 28 nosler) and have run into a few issues as of late.

so question for you guys,

whats your tolerance on concentricity when sizing brass?

im reloading for a 28 nosler using hornady brass. i have an RCBS FL sizing die and get an average of .007" run out when sized one time. i can get .0015"-.003" thou if i twist the brass in the shell holder a few times and size after each twist, but am i over working the brass doing that? and is hornady brass notorious for this type of issue? are the dies having issues? should i order a bushing die (forster,redding). does my press got too much slop?(rock chucker press). i have yet to check uniformity of the case necks as ive read that could be an issue too. ive just ordered some nosler brass and will test a few of these things out there too. sorry for so many questions but those are a few that i have. what are your thoughts? am i worrying about nothing?
I dont like the fact that i see that much run out on the necks.
thanks for your thoughts.

 

[Rol_P]

Are you de-priming as you resize? If so is your expander button high on the neck of the de-priming stem?
I have found improved concentricity using a de-primer die as a separate step in reloading. After reading some about the whole reloading process I switched to sizing the necks with a mandrel in a separate die. The case is firmly set in the shell holder as I push the mandrel down through the neck.
Conversely, using a button on the de-priming stem you are pulling the button up into the neck while the case base is tight against the under side of the groove in the shell holder. My feeling is the case is more secure and centered in the mandrel die leading to imporved concentricity. YMMV.
I hope this helps. Rol

 

[ElmerThud]

Are you de-priming as you resize? If so is your expander button high on the neck of the de-priming stem?
I have found improved concentricity using a de-primer die as a separate step in reloading. After reading some about the whole reloading process I switched to sizing the necks with a mandrel in a separate die. The case is firmly set in the shell holder as I push the mandrel down through the neck.
Conversely, using a button on the de-priming stem you are pulling the button up into the neck while the case base is tight against the under side of the groove in the shell holder. My feeling is the case is more secure and centered in the mandrel die leading to imporved concentricity. YMMV.
I hope this helps. Rol

This is pretty much spot on.
Use a universal de-cap die in a separate operation.. the re-sizing die de-cap rod should be raised until the expander just passes through the case neck.
When setting up the de-cap rod... leave it loose, run a case into the die allowing the loose rod expander to pass just through the case neck, then as you withdraw the case and feel the expander re-enter the case neck, hold the tension there with the press and tighten the de-cap rod.

You should now have the die completely concentric to case body/neck.

Any run out you find when measuring case neck/body will be differing thickness of brass on the case neck. You should find the difference not greater than .0005"-.0001"
.0005"-.0001" really is not worth bothering about - certainly not for hunting anyway.

As a side note, personally, I have a rubber 'O' ring under the locknut on the die.. gives some extra aligning case/die movement rather than just relying on the slippage in the shellholder.
Using Norma brass, I rarely have case neck/body run out greater than .0005"
That's just me though.
Good luck

 

[hhunter23]

ive pulled the expander ball up as high as i can while still allowing de-capping. i still get a lot of run-out with this set up. ill try these options suggested and go from there. thank you for the replies. i appreciate the help!

 

[ShadeTree]

I don't have a way to measure concentricity. Never bothered with it because I can maintain excellent groups with rifles that are capable of doing so.

However I've followed the above steps because that all made sense to me, as I moved along and learned to get better in the reloading process.

I had a universal decapping die purely by accident for decapping pistol cases that were then used to supply the cut off rims to my wife, which she used in crafts she makes to resell. I could feel less resistance overall at the bottom of the press stroke, and a more consistent feel in the press handle when resizing already deprimed brass with the UDD, so that's how I've done it since.

Decapping rod stem I set up as Elmer referenced above. I believe I picked that up from Scotty on here if I remember correctly.

On the step after sizing, you can also change the neck/shoulder alignment in the trimming process with a lathe trimmer. Even more so with freshly annealed brass. Wont take up space with some of the reasons I believe why this is, but I've intentionally experimented with this and get superior results by not taking big bites off the brass. I keep brass trimmed just .002 below max. Your results may vary.

At the end of it all, the method of chamfering/deburring the case is important for concentric bullet seating. As is the process of seating the bullet itself. We all probably have our own methods/beliefs as to what is the right way to do this. I don't measure concentricity, I just use ways that continue to work for me.

 

[1Shot]

Like has been said I also do not have the equipment to measure run out nor have I concerned myself with it in 41 years of hand loading. Then again I am not a serious long-range match shooter trying to achieve the last bit of accuracy possible.
I have just worked up accurate loads and if one bullet was a bit outside a group I attributed it to me or wind or something else.

But in your case I might suggest that you get a Lee Collet Die. FL size with your current die and then just run the cases into the Collet Die which only sizes the neck and aligns it with the mandrel.
All the measuring in the world will not fix your problem if you do not have concentric neck wall thickness. You must turn your necks to make them the same thickness all the way around or you are spitting into the wind.

 

[joelkdouglas]

Other steps that might help.

First, if you are asking how to improve concentricity that tells me you have a concentricity gauge. Terrible things! Just kidding. But after every change you make I would recommend testing it out--did it improve things or make them worse?

Elmer Thud already mentioned the O ring trick. Another place you can put an O ring is on the shellholder instead of whatever RCBS uses to keep the shellholder in place. This allows the shellholder to move just a smidge to align with the die. Warning: I did this with my Lee press and it was a destructive process. I can't use the regular shellholder attachment anymore because it was a metal spring like holder that's bent now.

What kind of shellholder are you using? For instance I've seen improved concentricity with Redding shellholders over Lee. The Lee shellholders hold the case very snug and the Redding allows the case a little slop, again letting the case wiggle/center in the die a bit.

I will often size a case, rotate it, size it again. I get good concentricity. I personally won't shoot at anything meaningful with a loaded round more than 0.005 out of 'round'. I don't see less brass life doing this.

You don't mention your concentricity gauge. For instance, if you are using the Sinclair gauge you will get different readings based on where you measure, ie towards the nose of the bullet or on the ogive.

 

[Elkman]

I cannot say your worrying is unfounded because you really didn't explain what if any changes have occurred in your shooting or accuracy. If you see no change then yes your worries are unfounded. I have never measured the concentricity on a case in my lifetime. I have been loading for 60 years, and have learned to be slightly more picky about my technique (my buddies shame me). But my four most used rifles consistently shoot under an inch, and one has done so for 50 years, which seemingly is accurate enough for my hunting needs.

 

[hhunter23]

well after all my testing and measuring, ive found that concentricity isnt affecting my accuracy. i will still continue testing. i did order a sinclair mandrel die, and even using a universal dacapping rod in my sizer die, i still see runout as much as .007". i like the mandrel die for neck sizing as it seems to be more consistent. i shot 3 different bullets trying to find a load. berger 180vlds, 175LRAB, 175ELDX. the bergers shot the best out of my rifle, but for hunting im leary to use them as ive heard and seen many horror stories. im still going to test the LRABs and see if i can get them to shoot better. the ELDX shot pretty good and i think i can tighten the group up and test more at longer ranges.

 

[hhunter23]

here are a some groups i shot.