as someone previously had happen, i got some reloads that were very difficult to chamber. and my reloading technique is to body only resize using redding body only die, trim case mouth, clean in tumbler, neck only resize, chamfer neck, and finally seat bullet. so my lengths werent too long and my body was resized each time. rounds on 5th reloading and are annealed after 3 firings. chamber is saami (.297 i think). i use a .293 redding titanium nitride bushing.
so i decided to buy some neck turning gear following this guide Neck Turning Basics. bought a KM kit with the carbide mandrel, sizing mandrel and a ball micrometer.
as it turns out some of my case necks openings were overly thick. I suspect this was the problem i was having. Turning the necks took care of this and also took care of any donuts.
so i bought a new box of 260 lappua cases and decided to slowly work these up. i use a foster coax press.
as the articles suggests i bought a hornady new dimension full length sizer. i also have a concentricity gauge.
so i did the following and this is where the question arises.
1. test concentricity of untouched case. usually less than 1 thou (unless dinged mouth which a few have)
2. lube and run through hornady sizer. runout remains less than 1 thou
3. lube mandrel and run new case.
4. test concentricity (now as much as 5 thou!)
5. measure case thickness with ball micrometer. almost always 14.5 to 15.5 thou
6. carefully turn cases to take off just a tad of brass, looking for 15 thou
7. measure on concentricity gauge, still 4 to 5 thou runout on case mouth
so.. i start looking at how the mandrel runs up into the case mouth. and if you slowly raise the shell onto the mandrel the case appears to be off center with the mandrel slightly out towards the front of the press. and this is where the runout is always highest.
so i'm using a foster coax, with foster coax ring and the mandrel die set firmly in the wring and the ring firmly as far into the slot as it will go but the case needs to come out some or the die needs to go in some (I think)
note that if i run the case back through the full length die the runout goes back to zero. but the bothersome thing is the mandrel will not center (apparently) correctly with my setup.
what started this whole process was i had some very good loads and they started to get some significant vertical dispersion. i finally tracked it down to neck tension and i am getting better results with the case necks cleaned up, even with older cases. but since if started down the concentricity and neck tension rabbit hole, i found this new issue which i wonder if others have had. and if so how do you address this issue.
so i decided to buy some neck turning gear following this guide Neck Turning Basics. bought a KM kit with the carbide mandrel, sizing mandrel and a ball micrometer.
as it turns out some of my case necks openings were overly thick. I suspect this was the problem i was having. Turning the necks took care of this and also took care of any donuts.
so i bought a new box of 260 lappua cases and decided to slowly work these up. i use a foster coax press.
as the articles suggests i bought a hornady new dimension full length sizer. i also have a concentricity gauge.
so i did the following and this is where the question arises.
1. test concentricity of untouched case. usually less than 1 thou (unless dinged mouth which a few have)
2. lube and run through hornady sizer. runout remains less than 1 thou
3. lube mandrel and run new case.
4. test concentricity (now as much as 5 thou!)
5. measure case thickness with ball micrometer. almost always 14.5 to 15.5 thou
6. carefully turn cases to take off just a tad of brass, looking for 15 thou
7. measure on concentricity gauge, still 4 to 5 thou runout on case mouth
so.. i start looking at how the mandrel runs up into the case mouth. and if you slowly raise the shell onto the mandrel the case appears to be off center with the mandrel slightly out towards the front of the press. and this is where the runout is always highest.
so i'm using a foster coax, with foster coax ring and the mandrel die set firmly in the wring and the ring firmly as far into the slot as it will go but the case needs to come out some or the die needs to go in some (I think)
note that if i run the case back through the full length die the runout goes back to zero. but the bothersome thing is the mandrel will not center (apparently) correctly with my setup.
what started this whole process was i had some very good loads and they started to get some significant vertical dispersion. i finally tracked it down to neck tension and i am getting better results with the case necks cleaned up, even with older cases. but since if started down the concentricity and neck tension rabbit hole, i found this new issue which i wonder if others have had. and if so how do you address this issue.
