Donuts vs. no donuts... Pressure Trace data

[Redhouse]

I'm not brand new to reloading, but am new to improved cases. I have a 260AI here and a bunch of .243 Lapua brass to neck up. I'm assuming but asking, is the donut only after firing? Has to be, right?

And - any photo's of the donut reamer in action? I looked at the linked site for the 15 MOA case taper, but understood him to say he was modifying the normal process - is that the basic process, sorta like a drill bit down the mouth of the case?

I think I better look closer in my Sinclair catalogue and see if they have something Thanks for the usefull info.

 

[kombayotch]

Yes, they appear after firing. However, I'm seeing some thickening at the base or the neck on even once fired brass. I wouldn't necessarily call it a donut, but there is some resistance when probing with various sized gage pins.

Originally, I just used a regular chucking reamer in a drill to get the donuts out. But, I've since purchased a K&M neck turning tool with the donut cutter on the pilot. It isn't any more work to turn the necks at the same time. I haven't modified the process as described in the link. However, I have heard an interesting suggestion, which was to bump the shoulder down 0.03" further than normal and turn the necks down to there. Then load the bullets hard into the lands to blow the shoulder back to the normal position.

The K&M turner with the donut cutter is shown here:
http://www.6mmbr.com/jgcaseprep.html

Sinclair doesn't carry K&M, these guys do:
http://precisionreloading.com/KMProducts.htm
or
http://www.lockstock.com

This is why I believe in throating match rifles so that the bullet remains ahead of the neck/shoulder juncture. This especially if dimensions are on the tight side and if necks are turned. Stay ahead of the donut and it's effects are minimized.

Not feasible in many situations, depending on the application. Tactical rifle shooters, for example, have a limited COAL due to magazine length restriction. Didn't pay for Badger Ordnance BDM bottom metal not to use it...