I measure the headspace brass with a hornady gauge and only bump .0015 after each firing. When I measure the brass after firing before I trim, it's .009 longer than loaded. Why is it growing .009 after a .001 bump with a body die? The load is lc brass, 155 sierra, and 45.4 gr Varget.
Brass growth??
- Thread starter jsthntn247
- Start date
when the brass is fired, we have mainly a migration of metal forward,where progressively the brass,from factory new ,is thinner,_ that will influence the shoulder height and the total brass height_
after the shoot, we try to control the shoulder height by bumping/lowering it, exactly as squeezing a toothpaste tube_
the lowering of the shoulder will squeeze down the shoulder height only, but the side effects of this squeezing, coupled with the stress induced from the previous shoot,will utterly emphasize the brass migration forward, and now the "forward" word is concentrated on the only brass part available for some growth:the neck_ and for this reason the total lenght of the brass is now bigger_
this "growth",or migration of brass forward, start from a little bit over the brass lower rim (at the opposite end), and this portion generally is where the most worn brass will fail (head separation)_ the zone of the future head separation progressively becomes thinner, from the brass migration mentioned above_
if we don't limit ourselves to control the shoulder height only, but we decide to full resize the same brass, the squeezing will happen pushing the brass dimensions from all the sides,not shoulderwise only:this way more brass even will be pushed forward,(often we can have a full resized longer brass,in need to be even more trimmed) utterly thinning the brass lower portion, until the separation,etc.
after the shoot, we try to control the shoulder height by bumping/lowering it, exactly as squeezing a toothpaste tube_
the lowering of the shoulder will squeeze down the shoulder height only, but the side effects of this squeezing, coupled with the stress induced from the previous shoot,will utterly emphasize the brass migration forward, and now the "forward" word is concentrated on the only brass part available for some growth:the neck_ and for this reason the total lenght of the brass is now bigger_
this "growth",or migration of brass forward, start from a little bit over the brass lower rim (at the opposite end), and this portion generally is where the most worn brass will fail (head separation)_ the zone of the future head separation progressively becomes thinner, from the brass migration mentioned above_
if we don't limit ourselves to control the shoulder height only, but we decide to full resize the same brass, the squeezing will happen pushing the brass dimensions from all the sides,not shoulderwise only:this way more brass even will be pushed forward,(often we can have a full resized longer brass,in need to be even more trimmed) utterly thinning the brass lower portion, until the separation,etc.
Is this only fixed by neck sizing? I would also assume that a body die made specifically for my chamber, to minimally under size the brass each time would also work?
You're on the point: assuming that we're talkin'about a bolt action,you're right when you talk about to a "body die made specifically etc..."_
even better if your bolt action would be a true racing-gun,aka bench-rest,where all the tolerances are keeped to the minimum available, and when we say "all", I mean that even the brass is adequately chosen in few pieces among a large batch,pampered,prepped,etc._
but that is like comparing F1 cars solutions to all other vehicles_
the same neck sizing only would slow the brass stretching & wear, but for sure don't stop his growing, and overall don't stop the migration (and thinning) of the same brass from his head (rim zone) to the neck, and don't necessarily would better the accuracy,in my opinion,on a average rifle_
a good part of Glenn Zediker's "Reloading for Competition" is covering this matter,by the way (strongly advised)_
about a custom body die etc.: if I would be competition-oriented, w/out money issues,and with the availability of U.S. market about that, that would be my choice, reminding,on the opposite side, that the chamber/die combos are quite expensive and tied together: once the barrel is toasted, the die would be only a sad orphan, and that for hunting or precision shooting as often seen here, the real close tolerances can be a burden if not a danger, in the wrong environment_
on the real world: every shoot will wear and modify your brass progressively until his retirement, whatever task could be adopted_the brass is born to be expendable, and his life has an end: we are happy that the brass is the least expensive part of this activity, and I think here the 90% of the members can live quite well,and shoot quite well, accepting this fact, handloading w.quality but not mandatorily custom tools...
my humble advise is to invest few $ on a Zediker's book, trim your brass when oversize, replacing it when worn_
personally I'm full-resizing-oriented,in a way or another but, again, it's only my opinion_
even better if your bolt action would be a true racing-gun,aka bench-rest,where all the tolerances are keeped to the minimum available, and when we say "all", I mean that even the brass is adequately chosen in few pieces among a large batch,pampered,prepped,etc._
but that is like comparing F1 cars solutions to all other vehicles_
the same neck sizing only would slow the brass stretching & wear, but for sure don't stop his growing, and overall don't stop the migration (and thinning) of the same brass from his head (rim zone) to the neck, and don't necessarily would better the accuracy,in my opinion,on a average rifle_
a good part of Glenn Zediker's "Reloading for Competition" is covering this matter,by the way (strongly advised)_
about a custom body die etc.: if I would be competition-oriented, w/out money issues,and with the availability of U.S. market about that, that would be my choice, reminding,on the opposite side, that the chamber/die combos are quite expensive and tied together: once the barrel is toasted, the die would be only a sad orphan, and that for hunting or precision shooting as often seen here, the real close tolerances can be a burden if not a danger, in the wrong environment_
on the real world: every shoot will wear and modify your brass progressively until his retirement, whatever task could be adopted_the brass is born to be expendable, and his life has an end: we are happy that the brass is the least expensive part of this activity, and I think here the 90% of the members can live quite well,and shoot quite well, accepting this fact, handloading w.quality but not mandatorily custom tools...
my humble advise is to invest few $ on a Zediker's book, trim your brass when oversize, replacing it when worn_
personally I'm full-resizing-oriented,in a way or another but, again, it's only my opinion_
What about polishing the inside of the body die a couple thousandths so it only resizes the body diameter .001?
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I've never tried_
I'm limited to a standard Redding body-only+ Wilson neck + Sinclair xpander for .308 & .222rem.
with some future experiment about S-type Redding on 8x57_
I'm not so advanced nor I own rifles so special to push me to modify the Reddings,aside removing their expanders _
I'm limited to a standard Redding body-only+ Wilson neck + Sinclair xpander for .308 & .222rem.
with some future experiment about S-type Redding on 8x57_
I'm not so advanced nor I own rifles so special to push me to modify the Reddings,aside removing their expanders _
