Forster Coax press with Redding Comp dies

[srvet]

Can I ask Coax users and others of course for some advice. I have recently changed from a vanilla ice cream RCBS Reloader special press that uses snap in shell holders to a Coax with the universal shell holding jaws.

I have noticed some concentricity issues have developed during the neck sizing process. I have always kept runout on the case necks to 1 thou or below but recently have noted runout increasing to 5-6 thou measured off the case neck after neck sizing with a Redding micrometer top bushing neck die . I have checked the fired cases before sizing and they were sub 1 thou runout but then immediately after sizing the runout was around 5 thou. Have any other users experienced such a thing. My current suspicion is that the sliding chamber that centres the case may be touching the shell holder jaws before the case has fully engaged the sliding chamber. The solution might be to shorten the sliding chamber to allow the shoulder of the case to fully engage in the chamber. Before I butcher a set of fine dies I would appreciate the collective wisdom of the forum.

Cheers

[DaveT]

Always hard to diagnose without seeing but worth checking no dirt in the jaws which might skew the case and same for bush...ie is it sitting in the die with a little slack such that you can hear it rattle...it needs to self-centre and may not do so if screwed down tight in the die.

[srvet]

The jaws are clean and the bushing rattles freely. I should have added that when I size the cases with a standard FL Forster die with expander ball without bushings the cases return to sub 1 thou runout. It seems that there might be a mismatch between the Coax shell holder assembly and the sliding sleeve of the Redding competition die.

[Ronin]

Simon, not sure if this is possible with the Co-ax die mounting, but putting a O ring bettween the lock ring and top of the press mount plate (where the die screws into, is a way of "floating the die" to align the die with the case and enable concentric sizing.

[srvet]

The die is floating all the time anyway as the die doesn't screw in, the lock ring clicks into a slot that allows the die to shift in and out. The case is held in a universal shell holder that allows left -right movement, therefore allowing movement in both planes. It just seems odd that the 308 comp neck sizer die seem to induce runout that I never saw on the old press, but when I use your Forster FL die it reduces the runout back to what I expect. I guess one thing to do is go back to the old press and check if that sorts the issue.

[Laurie]

Are you using Forster (or Sinclair) lock rings on the die? The standard Redding ring is too small diameter and thin for the snap-in Co-AX. You can have too much die-float! This press is designed to be used with Forster lock rings, and that's why they're available separately from dies in packs.

[srvet]

Are you using Forster (or Sinclair) lock rings on the die? The standard Redding ring is too small diameter and thin for the snap-in Co-AX. You can have too much die-float! This press is designed to be used with Forster lock rings, and that's why they're available separately from dies in packs.

All Forster lock rings. I tried the Redding ones but didn't like how loose they were!

[ds1]

I use the Forster co-ax with Redding comp dies in 308win. Also use the Forster lock rings. Not experienced a run out issue but one thing I had to do with the Forster shell holder system was to make sure the sliding plate mechanism had enough movement for the jaws to slide but no more than that - originally it seemed too slack as the die touched the jaws you could see some "spring " in it, which could be giving you run-out issues. Try lubricating inside the sliding jaws slightly but tighten the jaws down firmly - but not so much that they bind. You might then need to mess around with the position on the mandrel that opens the jaws. Again I found that I needed to add a lock nut to this, otherwise it kept coming loose and changed how much the jaws were opening.

[srvet]

Thanks for the replies, all of them greatly appreciated. I raised the question with Redding and Forster. At this time I have had a reply from AJ at Redding that gives a different explanation. It is as follows:

 

Because the FL Die is supporting the body of the case (as it is being resized) at the same time that the neck is being sized, it is not unusual to get very good concentricity.

 

When using a Busing Neck Sizing Die, the runout will typically reflect the quality (more precisely, the thickness variation) of the case itself. If a case varies more than about .001 in thickness from one side to the other, it will be difficult to resize it concentrically. Have you sorted your brass with a ball micrometer or case neck gauge for thickness? Sometimes, sizing the neck in two steps (in smaller increments) with an intermediate size bushing will help.

 

I hope this helps, have a great day.

 

 

So there you go! Variations in neck thickness (probably!)

When I think about it my previous reloads using the comp die have all used lightly neck turned (60-70% of circumference) Lapua cases, whilst the recent batch used once fired Sako cases without any neck turning. I guess it may be time to break out the neck turner again!

[Laurie]

Hmmm ... interesting. (But I'm not 100% convinced.)

 

What are the runouts like on the loaded rounds? That's what counts at the end of the day. The first time I used expensive 'Competition' bushing dies many years back when hardly anybody used these things, I was like you distinctly unimpressed by the sized case-neck runouts. However, charge the case and seat the bullet and nearly all of the runout disappeared. No - I couldn't explain it then, or now.

 

FWIW, the favourite top US / Canadian 223 Rem FTR shooters' sizing regime these days is to use a Redding (or whoever's) body die to get the case-body / shoulder bump setting right, then the cheapo Lee collet neck sizer. I've tried it myself and was so impressed, I now use my Forster Bushing-Bump die on 223 sans bushing to 'bump' the shoulder only, before using the Lee die. It gives better results than using a bushing followed by mandrel expander - and that's with neck-turned brass.

[srvet]

Thanks for all the help from you all. Just a quick update...

I had a response from Forster who advised to check the detention screw that holds the lock ring was not too tight (it wasn't) and to strip and clean the bushing die.

Subsequently i dug out a batch of 40 Lapua 308 cases that had been through my stalking rifle. These had all been neck turned in the past. I measured concentricity before sizing and got results of 0 to 2.5 thou. I then sized them using the same bushing die with a slightly larger bushing. Each case was measured with the concentricity gauge which showed the maximum runout to be 1 thou. To me this suggests that the combination of the Coax press and competition dies are capable of producing concentric cases (phew) , although this may be due, at least in part to the change in bushing that worked the brass less. What it also suggested to me was that I should not automatically assume that the more complex reloading techniques will automatically produce better results without equal care with case prep. Indeed these competition dies are building a personality akin to a show biz diva....brilliant so long as everything else is almost perfect!!

[gbal]

.'..so long as everything is perfect'....indeed,simply the old adage about the weakest link defines the chain's strength applies....

 

That can be any component,or the process,or the rifle rig,or the final nut behind the butt....

....but quality always helps-though becomes asymptotic ...diminishing returns...as perfection approaches...but that's a 'problem' we would all like to have...!!

 

gbal

[JTexas]

I just had a similar problem with bullet run-out, rather than case neck run-out, on new brass. While I'm still stumped for the present as to the precise cause, I did discover a couple of fixes to case/die alignment adjustment issues that may have been at issue. You might want to try them.

I had noted alignment problems, especially with .223 case necks hitting the side of a die. I noticed that my floor plate jaws were skewing my cases a bit from vertical. I found that with no die installed, and looking straight down vertically at the empty floor plate, I could see that the jaws were not symmetrical  around the primer discharge duct. The floor plate itself is slightly adjustable by loosening the two anchoring screws, centering the assembly while peering down from above, and then re-tightening the screws. That centered the floor plate, but the skewing of the case remained. One of the jaws seemed to be hitting the case a bit higher than on the opposite side. My jaw holder is a bit bowed in the middle, possibly from pulling on stuck cases. At any rate, I took the floor plate off the press and swapped the two jaws, then re-assembled and reinstalled it, centered. No more skewing!

Now my case was centered on the floor plate and aligned vertically in the jaws, but it was still slightly misaligned with the die, which has round Forster lock rings. The detente that holds the locking ring in the back of the die slot was properly adjusted, and I fiddled with bringing the die forward to the detente, and then pushing it all the back to its stop. My case misalignment disappeared when I brought the die forward to the detente. As a fix, I thought to place a spacer in the back of the die slot, to in effect move the stop forward to keep the die locking ring closer to the detente. I used a 3/8" round, self-adhesive felt pad, a bit over 1/16" thick. We put them on the backs of cabinet doors to mute the sound of them slamming shut. The fit was tight, so I wedged it in the back of the slot using needle-nose pliers to center it and and a hex wrench to push it back. Now there is still the slightest play in the die's movement, fore and aft in the slot behind the detente, as there needs to be for proper self-alignment with the cartridge, but not so much that the die can be pushed back so far that it can get held in serious misalignment. As I final measure I greased the slot surfaces to help keep dies mobile and unstuck.

I was not fully aware of the several points where small mis-alignments can occur and become additive on the Forster Co-Ax press, but I am now satisfied that I can adjust and mitigate them.

[Xtrema]

On 01/05/2017 at 4:32 AM, ds1 said:

You might then need to mess around with the position on the mandrel that opens the jaws. Again I found that I needed to add a lock nut to this, otherwise it kept coming loose and changed how much the jaws were opening.

Mine gradually comes loose also. Can you recall what the thread is as a lock nut would be a good idea for me too.

[Big Al]

On 30/04/2017 at 9:14 PM, srvet said:

Can I ask Coax users and others of course for some advice. I have recently changed from a vanilla ice cream RCBS Reloader special press that uses snap in shell holders to a Coax with the universal shell holding jaws.

I have noticed some concentricity issues have developed during the neck sizing process. I have always kept runout on the case necks to 1 thou or below but recently have noted runout increasing to 5-6 thou measured off the case neck after neck sizing with a Redding micrometer top bushing neck die . I have checked the fired cases before sizing and they were sub 1 thou runout but then immediately after sizing the runout was around 5 thou. Have any other users experienced such a thing. My current suspicion is that the sliding chamber that centres the case may be touching the shell holder jaws before the case has fully engaged the sliding chamber. The solution might be to shorten the sliding chamber to allow the shoulder of the case to fully engage in the chamber. Before I butcher a set of fine dies I would appreciate the collective wisdom of the forum.

Cheers

Does the Redding Micrometer bushing die with the same bush give sub 1 thou runout when used in a normal press?