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10 Reloading Steps -- Sinclair Info

I was just reading today's bulletin and the poster states that you should trim and then resize. Isn't that backwards? I was told years ago that you resize and then trimmer. Have I been doing to wrong all these years?
 
Ditto. I anneal, resize, then trim.
Those instructions from the bulletin were in the Sinclair precision reloading book from ~ 20 years ago.

I believe that resizing can add to the case growth in the neck area (very slightly), which is why I trim after. Following the Sinclair instructions as stated it may not be optimal, but better than not trimming at all.
 
The Bulletin article, from Sinclair, shows one technique, thinking mostly about new brass. Yes you can size and trim as well. For most cases, I actually inspect for neck defects first, run an expander down the necks to iron out dents, then do a quick, light chamfer and deburr. But I trim AFTER fireforming (if none of the cases are too long to chamber properly). Otherwise you may be trimming more than necessary. You may find that the case OAL is more consistent after one firing. YMMV, but with 6BR brass I like to shoot them once before trimming (unless one is way out of spec). What I've found is the "short brass" often extends a bit so you don't have to trim the longer ones as much to match.
 
It seems like I find that there are always some "long" cases even with new brass so I just got in the habit of sizing and then trimming. If I have one or two that are way short, they get culled out for barrel warmers.
 
Sizing reduces the neck so it fits better on the trimmer mandrel. Sizing also removes any out of round in the neck so you get better i.d and o.d. chamfers.
 
I do trim first before resizing because for me, it's more convenient as explained below.

Most new cases contain a "rough" edge at the end of the neck that can peel off brass particles when sizing that can eventually can scratch the inside neck portion of the die. This has happened to me in the past. It doesn't ruin the die but you end up with vertical scratches on the outside of the neck of the case. Again it doesn't affect performance of the case but it's a situation I like to avoid so I always want to chamber before I run new case into a die. This alone is not a reason to trim first but read on.

I like to deburr the primer flash hole and it much easier with the Sinclair tool if I place the case in a Wilson trimmer case holder. This gives me a much better hold of the case and it's much easier to use the tool.

So with the case in the Wilson trimmer case holder to deburr the flash hole and the desire to chamfer the necks before I size, it's make sense to trim after I deburr the flash hole. The burring tool also smooths out any dents in the neck (for 223 and 243). Next I trim then chamfer. By doing it this way I only have to chamfer once.

Next I full size with zero shoulder set back then uniform the pockets. By trimming before sizing I only have to chamfer once and I can ensure that all dents in the neck area are smoothed out plus I only have to insert the case into the Wilson trimmer case holder once for deburring the flash hole and trimming i.e. I deburr the flash hole then trim the case in one consecutive operation.

I don't believe either way is wrong, i.e. trim first or size first. You should be setting the full sizing die on zero shoulder set back anyway and zero extrusion by just touching the shoulder on new cases being sized before fire formed in the rifle chamber.
 
I trim after I resize. But overall the article and information is really good for a refresher and should be read by all new reloaders.
 
I run the appropriate size carbide pin through the case necks on new brass. This removes any case neck deformations. It also opens the case neck to achieve the neck tension I want (.0015" for new brass). Then I lightly chamfer the neck i.d and o.d. Then I prime and load and fire form. This is all I do to new quality brass for the first firing (Lapua or Nosler Premium).
 

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