Tuning the Redding T7 Primer

[justindad]

I did not use my on-press primer installer for a long time because it would only seat primers flush and that required a lot of force. I would try it every time I came across new brass - some worked better than others, and the system seemed to get better as parts wore in together. Some calibers worked better than others.
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Then one day I destroyed a primer because the primer installation ram was not concentric with the primer pocket of the case.


The concentricity between the case and primer installer vary quite a bit across different shell holders, which exacerbates the main issue that is my priming arm is just too short.
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I can’t make the priming arm longer, but I was able to remove most of the wobble it had when installed on the press. Here are the changes I made:
1) My mounting screw was too long, so the pivot bushing was loose. I shortened the screw until the bushing could not be rotated when only the screw & bushing were installed on the press.
2) The chamfer on the inside diameter of the bushing was smaller than the blend radius of the screw head. So I used a case mouth chamfering tool to enlarge the chamfer until they screw head would seat flush against the face of the bushing.
3) The bushing was 0.002” longer than the width of the priming arm. So I used a knife sharpening stone to grind the bushing until it was only 0.0005” longer than the width of the priming arm.
4) The cup that holds the primer had burrs, so I used a fiber wheel with polishing compound to remove the burr.
5) I used that same wheel to polish other rough areas of the cup, priming arm, and even the spring (which had wear marks).

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I can now install my primers to 0.006” deep without excessive force and I no longer damage primers. It works much better. I will be contacting Redding to see if they can get me a longer priming arm.

[reedap1]

I have recently begun using a Redding T7 Trret press. My first batch of 357 Mag cases was processed well until I got to the priming process. I too found it problematic and had several cases with bad primers installed. Overall the whole priming assembly seems sloppy with tolerances and clearances. I am going to make the modifications you have suggested and try again. The one main advantage I see to using the T7 is that I can mouth expand and prime in one action, though in reality, I can prime pretty fast separately on my RCBS Bench primer tool.

Thanks for the suggestions.

Paul