While I was working up a load for my ,257 Weatherby I was reading some posts about runout or concentricity and started checking my brass and I had a consistently large runout on the neck (.004 - ,006). When I check the runout on a fired case before depriming I am at .001 - .002 Trying to find the cause I took apart my decapping die and the decapping rod was caked with gunk. While I was cleaning it out I got to thinking about running the case through the first time to pop out the primer and then running it back through with the mandrel removed. I tried it and discovered that the mandrel was causing the large runout. When I ran the case back through the die without the mandrel I was still around .001. I use an expander mandrel to size the neck so I don't think I really need to size it with the expander/decapper rod. By doing this I can keep my runout to very acceptable limits. Does anyone else do this or have any thoughts about this idea? I'm getting past my comfort zone so I want to make sure I'm not screwing up.
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solving runout by removing expander rod
- Thread starter bonefish
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Lefty7mmstw
Well-Known Member
As long as your I.D. isn't more than two thou. smaller than your bullet diameter you'll be fine. Any more than that and the bullet will start to stretch the neck off center when you seat it.
Mikecr
Well-Known Member
Things you can do to produce low runout(straight) loaded ammo:
-Fire-form brass
-Hand de-prime with one of these: DECAPPING TOOL
-Partial neck size(downward)
-Size body absolute minimal
-Pre-expand necks with one of these: SINCLAIR GENERATION II EXPANDER DIES | Sinclair Intl
-Seat bullets in 2 steps ~60-90deg apart
-Verify low TIR with measurement on a v-block gage
Of course neck turning reduces some runout. And unless you're lucky enough with your seating die/press/shellholder, inline seating is often straighter.
-Fire-form brass
-Hand de-prime with one of these: DECAPPING TOOL
-Partial neck size(downward)
-Size body absolute minimal
-Pre-expand necks with one of these: SINCLAIR GENERATION II EXPANDER DIES | Sinclair Intl
-Seat bullets in 2 steps ~60-90deg apart
-Verify low TIR with measurement on a v-block gage
Of course neck turning reduces some runout. And unless you're lucky enough with your seating die/press/shellholder, inline seating is often straighter.
All the brass I am using has been fire formed. I don't have any new brass left. I also use the Sinclair expander die and all my necks have been turned but I don't use a neck die or a hand deprimer. If what I'm doing doesn't work. I'll try them. I'm not a 1000 yd shooter but I hunt in Colorado so 300 - 400+ yard shoots are certainly available. Handloading to me is a hobby and a challenge and I'm trying to get groups as tight as possible.
MontanaRifleman
Well-Known Member
BY removing the expanding mandrel you are making your bullet the expanding mandrel. NOT good IMO. What is your runout after seating the bullet in a neck that has not been expanded?
Here's what I do. I put a little impreial sizing way on the expander ball before sizing and take my case and stick the neck into imperial sizing wax and give it a twist and then size as normal. Works great.
I just did a once fired 300 RUM case in a standard Reading FL sizer and removed the expander then resized with expander.
Prior to sizing, runout was ~ .0005, OD .340
Sizing without expander, runout was ~ .0005, OD .330
Sizing with expander, runout was ~ .0005, OD .334
After seating with Comp seater, total runout was < .001, OD .336
This technique works great for me. IMO, if your neck diameter is being stretched more than 3 or 4 thou by seating the bullet it's probably not best for accuracy. I like the neck to be stretched (neck tension) somewhere in the 1-2 thou range by bullet seating.
Ideally, I would like the down stroke to produce an OD 1-2 thou smaller than the expanding up stroke. This is where a type S or similar FL bushing die is good. I am in the process of changing to this type of sizing (no neck turning). Use a bushing with expander to move neck irregularities out and minimal brass neck working.
Here's what I do. I put a little impreial sizing way on the expander ball before sizing and take my case and stick the neck into imperial sizing wax and give it a twist and then size as normal. Works great.
I just did a once fired 300 RUM case in a standard Reading FL sizer and removed the expander then resized with expander.
Prior to sizing, runout was ~ .0005, OD .340
Sizing without expander, runout was ~ .0005, OD .330
Sizing with expander, runout was ~ .0005, OD .334
After seating with Comp seater, total runout was < .001, OD .336
This technique works great for me. IMO, if your neck diameter is being stretched more than 3 or 4 thou by seating the bullet it's probably not best for accuracy. I like the neck to be stretched (neck tension) somewhere in the 1-2 thou range by bullet seating.
Ideally, I would like the down stroke to produce an OD 1-2 thou smaller than the expanding up stroke. This is where a type S or similar FL bushing die is good. I am in the process of changing to this type of sizing (no neck turning). Use a bushing with expander to move neck irregularities out and minimal brass neck working.
