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Seating die leaves ring mark.

14 Aug 2023
@ 02:14 am (GMT)

Magnus Hansson

I’m getting a ring mark on the bullet from the seating die, looks like shit but don’t seem to affect the groups at 100m (15mm). I don’t remembering having the problem with 150gr ..but it’s very noticeable with 165gr.

Why is this happening? And what can I do to fix it?

Cal. 308
Brass. Norma
Bullet. 165 SST
Die. Hornady



14 Aug 2023
@ 07:03 am (GMT)

Nathan Foster

Re: Seating die leaves ring mark.
Hi Magnus, hope all is well with you. I expect your hunting season is just around the corner.

Normally if a ring appears, it is a sign of somewhat excessive tension during initial sizing. This can happen with a Hornady die set if the tolerances are a little tight, especially if the expander button is a litter over polished. But in addition to this, you may find that your Norma cases have relatively heavy walls (leaving only around .003" clearance in the chamber). With such a thick necked case, you can imagine how much reduction occurs after running this through a tight necked die. Though Hornady dies have their uses, a Redding bushing die set is optimal under these conditions. The Lee neck collet dies are another option, a very useful and cheaper option but can be a little funky to work with during the learning phase (see mandrel observations / instructions in my reloading book).

Neck turning is of course another option if you want to go that route.

The above aside, you could give the seater button in your Hornady a bit of a polish. In a DIY setting - take a 165gr SST and apply valve grinding paste or some such to the ogive. Chuck the expander button in a drill and use the sacrificial projectile to polish out that particular spot. Finish with Scotchbrite or some such, then a rag and paste.

Alternatively, you might be able to obtain an ELD-M seater stem from your importer.

Do keep in mind, the problem is mostly likely related to neck tension versus the bearing surface of the 165gr (vs the easier seating 150gr). Changing the neck sizing diameter by +.001 or -.001" can have quite an impact on operations and outcomes (a need to be aware that very small changes can make quite a difference).

But as you say, if the rifle is grouping well then there is no great need to be concerned (at least within moderate ranges). The mark may create a fracture point but all this will mean is that (if it does have an effect), the jacket might roll back on itself rather than over expand.

OK, hope that helps a little bit.

14 Aug 2023
@ 08:28 am (GMT)

Magnus Hansson

Re: Seating die leaves ring mark.
Thank you very much, we do love our Norma brass over here ..who would have thought it might be causing this problem. Changing to eld seating stem might be the easiest way out. I was kind of thinking the jacket was super soft.

Swedish roebuck season starts Wednesday ..but with wild boars around we seem to hunt all year around these days. The 150gr have been fantastic, only a few left and I’m taking your advice from earlier and graining up to 165s.



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