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ShifuXPrivate
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Bump vs Full Length Sizing
03/03/2015
I understand the concepts. But can any FL die be used to bump?
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reloader112XFirst Sergeant
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Re: Bump vs Full Length Sizing
03/03/2015
(1 vote)
If you use a FL die to bump, you will also full length size the case. Just bumping the shoulders is over sold, just FL size and bump the shoulders back.
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spawnof918vXFirst Sergeant
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Re: Bump vs Full Length Sizing
03/03/2015
(2 votes)
No standard FL die on the market can bump the shoulder without first reducing it's diameter. Even Redding's body dies reduce the diameter of the shoulder and base. If you only wanna bump the shoulde you need to have a custom die made using your fireformed cases.
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HodgdonExtreme
XFirst Sergeant
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Re: Bump vs Full Length Sizing
03/03/2015 Last edited 03/03/2015 by HodgdonExtreme
Good kit, for certain purposes.
http://www.forsterproducts.com/store.asp?pid=36223
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spawnof918vXFirst Sergeant
Rating: 2.6/5 this site
3755 posts this site
Re: Bump vs Full Length Sizing
03/03/2015
It still sizes the shoulder.
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HodgdonExtreme
XFirst Sergeant
Rating: 3.7/5 this site
2605 posts this site
Re: Bump vs Full Length Sizing
03/03/2015
It does not size the body.
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spawnof918vXFirst Sergeant
Rating: 2.6/5 this site
3755 posts this site
Re: Bump vs Full Length Sizing
03/03/2015
(1 vote)
What is the shoulder diameter before and after the bumping operation?
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HodgdonExtreme
XFirst Sergeant
Rating: 3.7/5 this site
2605 posts this site
Re: Bump vs Full Length Sizing
03/03/2015
(1 vote)
That said, I did my best and measured several cases fired in my CBI-barreled Savage 308 at .453 plus a cunthair or two. So maybe ~.4532ish, perhaps, though again I caution attempting to quote such exact numbers for such an inexact measuring method.
Anyway, after using my Forster bushing/bump die to achieve .001" bump (having been zeroed on the fired cases), I could detect zero difference in the body/shoulder junction diameter; they still measured ~.453 + a cunthair or so.
I do not stand corrected.
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ShifuXPrivate
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Re: Bump vs Full Length Sizing
03/03/2015 Last edited 03/03/2015 by Shifu
For using an FL to size and bump, does that mean adjusting the die so that it pushes the shoulder back 0.001 to 0.002" from a fireformed case? This will in fact resize the rest case as well?
I saw the forster bump neck sizing die, which can bump. But it seem that if you use it in bump mode (with no bushing), it is really like a FL die?
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HodgdonExtreme
XFirst Sergeant
Rating: 3.7/5 this site
2605 posts this site
Re: Bump vs Full Length Sizing
03/03/2015 Last edited 03/03/2015 by HodgdonExtreme
(2 votes)
Yes, you've got the idea.
If you "bump" using an FLS die, you will be pinching down the body of the case a little. How much depends on the die you choose - ranging from ~zero with the aforementioned Forster bump die, to ~quite a bit using a small base die. A FLS die will be a little more than zero, and a "National Match" die will usually be a little more yet, but not as much as the smallbase. It'll also vary a little from one brand die to the next - and probably how early on in the die-reamers lifecycle it was used to cut the die.
All that said, I wouldn't overthink this.
Using a FLS die to bump shoulders back ~.001-.002" is what probably 95% of the shooters here do with great success.
There are probably reasons why uber-anal F class shooters and benchresters do things their own different way, but for a practical field rifle, the FLS die is the way to go.
If there is extra accuracy to be had by not sizing the body at ALL, it sure ain't much.
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ShifuXPrivate
Rating: 0.0/5 this site
34 posts this site
Re: Bump vs Full Length Sizing
03/04/2015
Thanks HodgdonExtreme and everyone else.
This makes sense now. Since I'm starting reloading, I'll definitely use the FLS die and may consider playing with the Forster bump die.
How do you find out small base or measurements of dies? I haven't seen any specs or measurements of dies.
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spawnof918vXFirst Sergeant
Rating: 2.6/5 this site
3755 posts this site
Re: Bump vs Full Length Sizing
03/04/2015
(1 vote)
Small base dies size the base .001" more than standard dies.
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spawnof918vXFirst Sergeant
Rating: 2.6/5 this site
3755 posts this site
Re: Bump vs Full Length Sizing
03/04/2015
(3 votes)
---------------------------------------------
--- HodgdonExtreme wrote:
That said, I did my best and measured several cases fired in my CBI-barreled Savage 308 at .453 plus a cunthair or two. So maybe ~.4532ish, perhaps, though again I caution attempting to quote such exact numbers for such an inexact measuring method.
Anyway, after using my Forster bushing/bump die to achieve .001" bump (having been zeroed on the fired cases), I could detect zero difference in the body/shoulder junction diameter; they still measured ~.453 + a cunthair or so.
I do not stand corrected.
---------------------------------------------
What happens when you bump more than .001"? Does the shoulder diameter increase?
What I'm getting at is that you can't push on one side of the case without affecting the other. You can't bump the shoulder without bowing the case walls. How do you deal with springback? Some cases spring back more than others? Some cases require more shoulder bump than others. How do you deal with all that?
By that definition a Lee collet neck die bumps the shoulder .001" as well.
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tucker301
XModerator
Rating: 3.3/5 this site
9950 posts this site
Re: Bump vs Full Length Sizing
03/04/2015 Last edited 03/04/2015 by tucker301
I've been trying to understand bump sizing for a couple of weeks now, and what was just said is what I have not been able to resolve either.
If you move .001 here, it has to go somewhere.
That and I have no idea how to set a FL die to only engage the shoulder and leave the rest of the case alone.
Rate now:
spawnof918vXFirst Sergeant
Rating: 2.6/5 this site
3755 posts this site
Re: Bump vs Full Length Sizing
03/04/2015
(1 vote)
You can't.
The only way to do this is to get a custom die made using specs off your fireformed cases. The wsy a FL die works is the body and shoulder get reduced in diameter first and this pops the shoulder forward. As the die finishes sizing the neck it finally contacts the shoulder and bumps it back which swages some of it into the neck. And so the case grows in length.
Rate now:
Rating: 0.0/5 this site
34 posts this site
Bump vs Full Length Sizing
03/03/2015
I understand the concepts. But can any FL die be used to bump?
Rate now:
reloader112XFirst Sergeant
Rating: 3.0/5 this site
1395 posts this site
Re: Bump vs Full Length Sizing
03/03/2015
(1 vote)
If you use a FL die to bump, you will also full length size the case. Just bumping the shoulders is over sold, just FL size and bump the shoulders back.
Rate now:
spawnof918vXFirst Sergeant
Rating: 2.6/5 this site
3755 posts this site
Re: Bump vs Full Length Sizing
03/03/2015
(2 votes)
No standard FL die on the market can bump the shoulder without first reducing it's diameter. Even Redding's body dies reduce the diameter of the shoulder and base. If you only wanna bump the shoulde you need to have a custom die made using your fireformed cases.
Rate now:
HodgdonExtreme
XFirst Sergeant
Rating: 3.7/5 this site
2605 posts this site
Re: Bump vs Full Length Sizing
03/03/2015 Last edited 03/03/2015 by HodgdonExtreme
spawnof918v wrote: No standard FL die on the market can bump the shoulder without first reducing it's diameter. Even Redding's body dies reduce the diameter of the shoulder and base. If you only wanna bump the shoulde you need to have a custom die made using your fireformed cases.
Forster makes what they call a "bushing bump" die, which only sizes the neck via bushing, and pushes the shoulder back. No body sizing performed.Good kit, for certain purposes.
http://www.forsterproducts.com/store.asp?pid=36223
Rate now:
spawnof918vXFirst Sergeant
Rating: 2.6/5 this site
3755 posts this site
Re: Bump vs Full Length Sizing
03/03/2015
It still sizes the shoulder.
Rate now:
HodgdonExtreme
XFirst Sergeant
Rating: 3.7/5 this site
2605 posts this site
Re: Bump vs Full Length Sizing
03/03/2015
spawnof918v wrote: It still sizes the shoulder.
Yes, that's the point - it pushes the shoulder back, and sizes the neck per whichever bushing you choose.It does not size the body.
Rate now:
spawnof918vXFirst Sergeant
Rating: 2.6/5 this site
3755 posts this site
Re: Bump vs Full Length Sizing
03/03/2015
(1 vote)
What is the shoulder diameter before and after the bumping operation?
Rate now:
HodgdonExtreme
XFirst Sergeant
Rating: 3.7/5 this site
2605 posts this site
Re: Bump vs Full Length Sizing
03/03/2015
(1 vote)
spawnof918v wrote: What is the shoulder diameter before and after the bumping operation?
First, understand that few of us have the tools/instruments required to truly measure the diameter of the case body where it intersects the shoulder. You can get close with a caliper, and shimmy the caliper up the body until it's just about to pop off the body, but it is not a highly accurate/scientific way to get the measurement.That said, I did my best and measured several cases fired in my CBI-barreled Savage 308 at .453 plus a cunthair or two. So maybe ~.4532ish, perhaps, though again I caution attempting to quote such exact numbers for such an inexact measuring method.
Anyway, after using my Forster bushing/bump die to achieve .001" bump (having been zeroed on the fired cases), I could detect zero difference in the body/shoulder junction diameter; they still measured ~.453 + a cunthair or so.
I do not stand corrected.
Rate now:
ShifuXPrivate
Rating: 0.0/5 this site
34 posts this site
Re: Bump vs Full Length Sizing
03/03/2015 Last edited 03/03/2015 by Shifu
reloader112 wrote:
If you use a FL die to bump, you will also full length size the case. Just bumping the shoulders is over sold, just FL size and bump the shoulders back.
So when people talk about bumping the shoulders, they usually mean using a FL die to bump the shoulders back (and resize)? It seems no one mentions about using custom dies in the tutorials or youtube videos.If you use a FL die to bump, you will also full length size the case. Just bumping the shoulders is over sold, just FL size and bump the shoulders back.
For using an FL to size and bump, does that mean adjusting the die so that it pushes the shoulder back 0.001 to 0.002" from a fireformed case? This will in fact resize the rest case as well?
I saw the forster bump neck sizing die, which can bump. But it seem that if you use it in bump mode (with no bushing), it is really like a FL die?
Rate now:
HodgdonExtreme
XFirst Sergeant
Rating: 3.7/5 this site
2605 posts this site
Re: Bump vs Full Length Sizing
03/03/2015 Last edited 03/03/2015 by HodgdonExtreme
(2 votes)
Yes, you've got the idea.
If you "bump" using an FLS die, you will be pinching down the body of the case a little. How much depends on the die you choose - ranging from ~zero with the aforementioned Forster bump die, to ~quite a bit using a small base die. A FLS die will be a little more than zero, and a "National Match" die will usually be a little more yet, but not as much as the smallbase. It'll also vary a little from one brand die to the next - and probably how early on in the die-reamers lifecycle it was used to cut the die.
All that said, I wouldn't overthink this.
Using a FLS die to bump shoulders back ~.001-.002" is what probably 95% of the shooters here do with great success.
There are probably reasons why uber-anal F class shooters and benchresters do things their own different way, but for a practical field rifle, the FLS die is the way to go.
If there is extra accuracy to be had by not sizing the body at ALL, it sure ain't much.
Rate now:
ShifuXPrivate
Rating: 0.0/5 this site
34 posts this site
Re: Bump vs Full Length Sizing
03/04/2015
Thanks HodgdonExtreme and everyone else.
This makes sense now. Since I'm starting reloading, I'll definitely use the FLS die and may consider playing with the Forster bump die.
How do you find out small base or measurements of dies? I haven't seen any specs or measurements of dies.
Rate now:
spawnof918vXFirst Sergeant
Rating: 2.6/5 this site
3755 posts this site
Re: Bump vs Full Length Sizing
03/04/2015
(1 vote)
Small base dies size the base .001" more than standard dies.
Rate now:
spawnof918vXFirst Sergeant
Rating: 2.6/5 this site
3755 posts this site
Re: Bump vs Full Length Sizing
03/04/2015
(3 votes)
---------------------------------------------
--- HodgdonExtreme wrote:
spawnof918v wrote: What is the shoulder diameter before and after the bumping operation?
First, understand that few of us have the tools/instruments required to truly measure the diameter of the case body where it intersects the shoulder. You can get close with a caliper, and shimmy the caliper up the body until it's just about to pop off the body, but it is not a highly accurate/scientific way to get the measurement.That said, I did my best and measured several cases fired in my CBI-barreled Savage 308 at .453 plus a cunthair or two. So maybe ~.4532ish, perhaps, though again I caution attempting to quote such exact numbers for such an inexact measuring method.
Anyway, after using my Forster bushing/bump die to achieve .001" bump (having been zeroed on the fired cases), I could detect zero difference in the body/shoulder junction diameter; they still measured ~.453 + a cunthair or so.
I do not stand corrected.
---------------------------------------------
What happens when you bump more than .001"? Does the shoulder diameter increase?
What I'm getting at is that you can't push on one side of the case without affecting the other. You can't bump the shoulder without bowing the case walls. How do you deal with springback? Some cases spring back more than others? Some cases require more shoulder bump than others. How do you deal with all that?
By that definition a Lee collet neck die bumps the shoulder .001" as well.
Rate now:
tucker301
XModerator
Rating: 3.3/5 this site
9950 posts this site
Re: Bump vs Full Length Sizing
03/04/2015 Last edited 03/04/2015 by tucker301
I've been trying to understand bump sizing for a couple of weeks now, and what was just said is what I have not been able to resolve either.
If you move .001 here, it has to go somewhere.
That and I have no idea how to set a FL die to only engage the shoulder and leave the rest of the case alone.
Rate now:
spawnof918vXFirst Sergeant
Rating: 2.6/5 this site
3755 posts this site
Re: Bump vs Full Length Sizing
03/04/2015
(1 vote)
You can't.
The only way to do this is to get a custom die made using specs off your fireformed cases. The wsy a FL die works is the body and shoulder get reduced in diameter first and this pops the shoulder forward. As the die finishes sizing the neck it finally contacts the shoulder and bumps it back which swages some of it into the neck. And so the case grows in length.
Rate now: