Bumping/neck sizing...when to FLS...?

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Bumping/neck sizing...when to FLS...?

Post by Stix » 06 Mar 2018, 7:14 pm

For varmint/hunting...
In short my question for the fireforming & neck sizing gurus is... ...

If you have JUST A FEW (lets say 5/50) cases in any given batch that are tight & need to be bumped back through the FLS die...

Are you best to run ALL 50 of those cases through the FLS die, so as to keep brass flow/neck & wall thickness etc the same...? (Even though they dont all need it)
... ...OR... ...
Is it ok to only bump those few cases with the FLS'er & throw them back in the batch...?


What do others do...?

In long--ive just fireformed 50 new cases & 5 or 6 of them are for some reason really really tight.
I usually dont like to go near brass with FLS die until at least 2 firings to make sure they are all fully formed (i always seem get some that are stragglers)...
In this case ive had to FLS these as they really were too tight, & ive bumped them back a thou--they now chamber beautifully.

But before i tumble them & mix them up, i wondered if FL sizing random oversized cases like that is not a good idea, especially when they will be wet tumbled & will loose track of which ones they were...
It is a curse of the ocd, but its hard enough keeping track of loads in books & how many times cases fired & keeping them weight sorted, let alone which ones have been FLsized/NKsized...
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Re: Bumping/neck sizing...when to FLS...?

Post by sungazer » 06 Mar 2018, 7:20 pm

There will always be a tolerance when you FLS I would be surprised if you could keep it at 1 thou or below.
When you say fireforming what size brass (do you start with) to what size (after fireforming) and the what size calibre FLS die are you using?
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Re: Bumping/neck sizing...when to FLS...?

Post by marksman » 06 Mar 2018, 7:29 pm

I would do all but am interested in why only a few are tighter
I'm thinking maybe you have tested different loads so the difference
are they tight to close the bolt or to open the bolt?

tight to close is usually neck
tight to open is usually body
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Re: Bumping/neck sizing...when to FLS...?

Post by Wm.Traynor » 06 Mar 2018, 8:07 pm

A few questions arise from your initial post Stix but I would say that if you have all those classifications (your last sentence), then you need a separate box for each.
Have you really weight sorted them? Are the cases that need bumping from different batches?
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Re: Bumping/neck sizing...when to FLS...?

Post by Stix » 06 Mar 2018, 10:41 pm

Right ill try again.....just spent 40 mins taking pics & typing & the fantastic samsung phone farted & lost it all...aaarrrghh...!!

*Its new Norma 204 brass being formed in a 204 rifle. (Sorry that's fire forming to me--to the chamber & neck size there after)

*Redding FL die

*They are (were) loaded with 8.5 grains of trailboss...
I did load them in a hurry & late at night but dont recall using different charge weights--im usually pretty dilligent with powder happening & always use 2 scales to check as i go--only one type of powder on the bench--even if i did use different charge, i cant see it would have been more than 9 grains of TB & that load has been proven in that same rifle, albeit with a different batch of Norma brass that weighs the same (+/- .2 grain), & i had no issues with those--infact those have not been FL sized at all yet & are on 4th firing. (actually they were already formed to chamber so would have had a bigger capacity).

*They were tight to close the bolt...i didnt think to check the neck before running them through the FL sizer.
The cases that were not tight to chamber were measured as 1.5525"-1.554" with one loner at 1.5545"--again they all chambered fine.
The cases that were tight to chamber were 1.555"-1.5565"--again these were notably tight to close the bolt (i dont recall the bolt lift).

The FL sized cases now measure 1.554" & chamber fine with no bolt tension.

As for weight sorting--all i did with these cases was to uniform & deburr the flash holes, neck size them, then give the necks a quick chamfer/deburr...
All the cases are from the same batch, & ive just checked them & the first dozen or so cases all weigh between 97.5-97.7 grains....(ive not yet got into checking volume with water--this is just a rabbit/fox gun).

At this stage im keen to hear peoples opinions on whether i should FL size the rest of the cases...is it detremental longer term accuracy & inconsistant brass life in a batch to have random cases FLsized & others just neck sized...?
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Re: Bumping/neck sizing...when to FLS...?

Post by sungazer » 07 Mar 2018, 7:21 am

If the cases that you have not FLS measure 1.5525"-1.554" and a FLS one measures 1.554 then I wouldn't size them. Dont worry about the necks as long as they hold bullets they will be sized when you seat the projectile and fire it.
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Re: Bumping/neck sizing...when to FLS...?

Post by marksman » 07 Mar 2018, 7:58 am

I'm the type that if I do it for one I will for all, ocd maybe :unknown:
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Re: Bumping/neck sizing...when to FLS...?

Post by Gwion » 07 Mar 2018, 2:24 pm

Run them through your neck trimmer. May be as simple as that.
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Re: Bumping/neck sizing...when to FLS...?

Post by Stix » 07 Mar 2018, 4:56 pm

Sorry guys--in my second attempt at the above post, i negated to point out that those measurements were to the shoulder using the hornady comparitor doova's in a caliper...
Those measurements are not the length of the case.
So the case length was not the issue.
Apologies for not being clear on that...
The trim length of a 204 case is listed as 1.840".
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Re: Bumping/neck sizing...when to FLS...?

Post by Gwion » 07 Mar 2018, 8:09 pm

Well then. Do to one, do to all. Painful but ... cheaper than a shoulder bump die.
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