Shoulder Bump Inconsistency on Co-Ax

[Straightshooter1]

I am annealing with a burstfire induction annealer every reload. Used the templique 750 deg paint to verify temps

750°F isn't enough. You really should be at ~1,100°F. . . particularly when using an induction annealer like the Burstfire.

Keep in mind the annealing process is a combination of the amount of heat + time.

 

[Stratofisher]

See if someone with a roll die will run your "pressure" brass for you, than try sizing again.

Thanks for the input- that roll die is pretty slick. Don't know anyone with one, but looks like a new reloading bench accessory in my future

 

[SeabeeKen]

Measuring on an ejector mark would also add a couple thou to the length. Perhaps filing off the ejector mark might give a more accurate measurement.
Id also back that load down.

 

[J.d. Popkes]

The die has been set to a .002 shoulder bump. This in my custom rifle I built that I am normally running single digit ES and SD on reloads. I had worked a ladder up with some N565,H1000, and N570 in an attempt to find the best powder combo in my 6.5 PRC. Have settled on N565 at a mid level as it offers the best accuracy at less than .3 MOA groups on most 5 shot groups. I probably should just remove the pressure sign brass and move on as the other all size appropriately. On these pressure sign brass the distance from the .200 line to case base is larger than the non-pressure brass. I can size all the non-pressure brass and the bump is exactly on with a .002 bump. These pressure signed brass will not size down with the same die setting in the Co-Ax. I hypothesize that is is something to do with the the way the jaws grip the case. I am getting a Co-Ax shell plate holder to try out to see if that is part of why this occurs. These brass on on their 4th reloads. Just something interesting I have found and was curious if anyone else had seen this happening.

I am getting a Co-Ax shell plate holder to try out to see if that is part of why this occurs

Okay since you are doing this, order the Redding comp shell holders too. Anneal every time, lube correctly, and watch the trouble disappear

 

[SSchnd]

Only thing I have ever seen with Coax press is one, make sure my primers are out as I get edge around the firing pin hit in my old M70. I can get .002 with that primer in the case when checking HS/Shoulder bump.
Should not be an issue as the primer hole is larger than the SRP or LRP primer so that (using the jaws) should not affect you actual bump, but will affect the case measurement.

As to the press I ONLY use Forster die rings for the Coax. If I use another die lock rings it is no bueno.

I get perfect measurements 1.169 on my BRA Lapua case either AMP or Giraud gas annealed.

 

[SKWERLZ]

I find those bump gauges that attach to a caliper very rickety. I get more consistent results from the RCBS Precision Mic. You screw a calibrated drum down over the case and the measurements are very repeatable.

Those are nice tools.

 

[J_idaho]

I assume you’ve figured out the problem by now. But I’ll just point out the the obvious that the swipe mark is standing proud causing .002” extra lengths. I will point out that if your goal is .002” bump then this should cause some resistance on bolt close. Gerard trimmers cut off shoulder and forester is bumping off rim so everything is probably working right. You just need to remove burrs prior to sizing to get measurements correct which might not come out perfect since coax is sizing off rim. You would have to size off base of case to avoid any variations. I forgot to mention avoiding swipes is the only real solution. As mentioned before.

 

[209jones]

Ejector dents or swipes are a material move of one form or the other, has to distort the rim face a bit when you can see it there. How much, good question, probably can't measure it easily, doesn't strike me as something reliably able to be determined with a caliper. Haven't got any feeler gauges handy, too cold to bother going to garage, sure a person can feel .003, not sure about .002, lay one on the table and see.

 

[Stratofisher]

I have discarded the few pieces that were not conforming. Only 6 pieces out of 200 that were at the high end of my test ladder. Shooting at a reasonable level to make sure that it is good for moderate temp days and the warmer days of summer. 57.1 Gr of N565 works like magic in my 6.5 PRC with the Berger 156's. Gets me a consistent 2940fps

 

[Gary O'Neal]

Do you have the stock linkage bars on the Coax or the curved aftermarket?

 

[Stratofisher]

Do you have the stock linkage bars on the Coax or the curved aftermarket?

I have the inline version aftermarket. Tried the curved and had spongy issues

 

[Gary O'Neal]

I had problems when I got my SAC sizing die. Call SAC and they said change back to the factory version and it cured the problem. It seems after market versions can change the timing and cause minute variations. You might give it a try.