Neck sizing or shoulder bumping

AL PALMER · July 23, 2018, 11:20 AM

What is your thoughts on bumping shoulders or neck sizing. does one give better accuracy over the other? Does neck sizing create bolt problems?

F. Guffey · July 23, 2018, 12:07 PM

Neck sizing or shoulder bumping

--------------------------------------------------------------------------------

Quote:

What is your thoughts on bumping shoulders or neck sizing. does one give better accuracy over the other? Does neck sizing create bolt problems?

What are my thoughts? I find it impossible to bump/move the shoulder back on a case with a full length sizing die. I have neck sizing dies, I also have full length sizing dies that can be used to neck size the neck.

My thoughts? I prefer to size the case with clearance; to consider case clearance I must know the length of the chamber from the shoulder to the bolt face. The term? "I bump the shoulder" comes from the method and or technique for controlling the length of the case from the datum/shoulder to the case head. And then there is 'BUMP', SBU as in shortly before us bump was used to describe the movement of the ram when it was raised. Most rams traveled up, stopped and then started back down at the top of the stroke. After that there was one of those 'and then' moments; and then presses had a change in design. The change eliminated the stop and return at the top. Old presses were identified as 'bump[ presses' and the newer design was described as a non-bump press.

I have bump and non-bump presses; the instructions do not drive me to the curb, the instructions are not alike, the instructions are different. And then came the internet; the term was such a catchy phrase/work reloaders that had never read the instructions applied 'bump' to everything that referred to sizing.

It is impossible to move the shoulder back on a case with a die that has full length case body support. Reloaders should have learned that when that started having trouble seating bullets and crimping at the same time. The first thing to go is the case body/shoulder juncture, it bulges.

F. Guffey

hounddawg · July 23, 2018, 12:13 PM

Erik Cortina explains why it is better to FL size and bump the shoulder back a bit. Even if you decide to neck size you will still need to bump the shoulder a bit with a FL resize when the bolt starts to become hard to close

http://bulletin.accurateshooter.com/...ze-your-brass/

cw308 · July 23, 2018, 12:40 PM

I use to neck size , with neck sizing all the cases aren't really the same length ,you just size the neck until you get resistance on your bolt lift or closing . I switched to full sizing with a case headspace between .001- .002 trim every time after sizing . Every case is as close to exact as possible for me F/L sizing is more accurate then neck . Heavy bolt lifts can cause galling on the bolts locking lugs with zero headspace also . Less wear an tare on the rifle . Hope I helped in some way.

Chris

T. O'Heir · July 23, 2018, 01:13 PM

How you size has nothing to do with accuracy. Sizing is about the loaded round fitting in the chamber.
Neck sizing is only possible with case that were fired out of the rifle you're loading for. And sooner or later you'll have to FL resize anyway.
You're not bumping the shoulder anywhere. You're resizing the case over its whole length. Neither dies nor presses are precise enough to move the shoulders just a few thou either.
"...case headspace..." There's no such thing as that. Headspace is a manufacturing tolerance only.

cw308 · July 23, 2018, 01:41 PM

T
I my not know the proper term , headspace , I do want to know the distance from the shoulder to base in the chamber , I full length size my fired cases to fit my chamber with .001 to .002 of room or what ever you call it . As far as my questions , I do like to know what rifle , action , caliber and the OP 's system in sizing , that's just me . Is he loading for hunting or target shooting , two different ball games . Again that's just me .

RC20 · July 23, 2018, 01:42 PM

AP:

Phew, you jumped into the Labrea Tar pit, your bones may be used in a Archaeologic Museum one day.

And then there is Mr. Guffey. Welcome to the group.

That said its a contentious issue and the simple answer, is, well.........

I do minimum shoulder bump regardless of how you express it (ala Mr. Guffy) to keep my cases from cracking at the base.

It really is a matter of what suits you. My take was if I had to full size every X rounds I might as well full size as no one agrees 100% on what the accuracy affect is.

There are a lot of answers but often not good scientifically proven ones.

F. Guffey · July 23, 2018, 02:24 PM

Quote:

And then there is Mr. Guffey. Welcome to the group.

Yes, he did not learn to reload by repeating what he heard and or read on the Internet. If he was in that category he would say the firing pin drives the case to the shoulder of the chamber. I understand CW308 was singing the praise of Bart B. on another forum. Many years ago I suggested to Bart B he needs to rethink his philosophy, I suggested he first determine where the case stretches. After that he got into calling SAAMI, I am sure SAAMI was impressed with Bart's shooting but SAAMI did not list case head space on there case drawings then and nothing has changed; SAAMI does not list case head space for the case in their drawings.

And then there is R. Lee in his book on modern reloading. R. Lee list case length from the datum/shoulder to the case head; R. Lee does not list chamber drawings. And I have books that go back to about 1954,

F. Guffey

hounddawg · July 23, 2018, 03:15 PM

Quote:

There are a lot of answers but often not good scientifically proven ones

For anyone who really wants to learn I suggest books by people like Brain Litz, Tony Boyer, Glen Zediker etc. Forums tend to have more opinions than facts and there is more than one right way to make safe ammo

craddleshooter · July 23, 2018, 03:53 PM

If your brass is once fired, using a suitable gauge such as the one Hornady has mislabeled their "headspace gauge", first try setting your die to replicate the head to shoulder dimension of once fired brass, (remembering to remove the primer before measuring the fired case). Try a case sized this way in your rifle. If it chambers OK then you are home free. The FL die will size the neck. Is your die one piece, or does take bushings so that necks can be sized differently depending on which bushing is used? In any case, be sure to lube the insides of your necks before sizing and if that lube is some sort of liquid or wax clean it out after sizing so the powder does not stick to it when you charge the cases. A good rule for reloading is to put powder in all of your cases and with them all in the same loading block, with good light. look down into all of them to be sure that they are all filled to the same level, assuming that they are the same load.

jpx2rk · July 23, 2018, 05:43 PM

The only way you or anyone will know is to try doing both and test your ammo.

J.G. Terry · August 1, 2018, 07:08 AM

Bump or neck size is a hot button topic on the net. I'd really like to know. I'm skeptical of partially FL sizing brass. How do I know that only thing done is bumping the shoulder.

How do I know this really fits the chamber? What does closing on the case really tell me? Frankly, this shoulder business sounds like voodoo reloading to me.

cw308 · August 1, 2018, 08:22 AM

J.G.Terry
Good question . After reading and kicking things around on this forum to give me a better understanding on what happens to the brass during firing lm comfortable with my system . I full length size every time . My brass was getting shorter after firing from expansion wasn't getting longer . When I full sized the case , the case squeezed down causing the case to become longer , checked with the RCBS Precision Mic . Ordered a Go Gage for my Rem. 700 308 Cal. the gage measures 1.630 bolt closed on the gage with no resistant with a .002 piece of shim on the bolt face the bolt closed with very little resistance , this gave me my chamber length measurement.

I ordered the Redding Competition shellholder set of 5 , different deck heights . This allows you to adjust your die off the shellholder without oversizing your brass . I can now size my case length to .0015 to .002 no longer or shorter . If you can strip your bolt , using only the housing , you can slowly size down your case alittle at a time an install the case in your rifles chamber until the bolt closes with very little resistance , that would be your zero case headspace . Hope I Helped in some way , sorry for being so long winded in explaining .

Chris

Don Fischer · August 1, 2018, 09:25 AM

Neck sizing and this thing called bumping the shoulder is what I've always done with FL dies. Not that long ago I got a set of those Lee collet neck dies and they seem to work great.

Neck sizing with a FL dies means nothing more than not allowing the die to reach and move the case shoulder. You can get any where from just a bit down on the case to almost but not quite the shoulder. You can see where the die stopped in the neck of the case. Just two or three loadings and your bolt will no longer chamber the case, it's grown to tight. At that point is where I've set my FL die for years. Trial and error and keep moving the die down and re-sizing the case until the bolt will close easily on it. Lot of guy's want to feel a bit of pressure by not taking the shoulder back quite all the way. When you have done this you have a case sized to fit the chamber of the rifle you sized it for. It may or may not fit in another chamber. Right there I lock the die in place ant it is never used except for that rifle again! I have been one to never keep two rifles in the same chambering but a couple years ago ended up with two 243's, both have their own set of dies. The cartridge's for one of them will not work in the other rifle, can't clost the bolt. Yet the cartridges in the other will fit in both chamber's.have the box's marked to keep the case's seperate.

My method of partial sizing I think is what is refereed to as bump sizing sizing. Actually you cannot bump size a case and move the shoulder without sizing the whole case the same amount. Once the case reach's the shoulder, the whole case will be touching the case. Now if the shoulder in your chamber is a bit long, the case being touched should support itself as you continue up. But if you hit the shoulder first I would think that without the case walls to support the case the case would buckle to some extent at the base of the shoulder, possibly keeping the case from chambering. The whole thing is partial sizing. The whole case is partial sized so it will fit one certain chamber. If you have not moved the shoulder enough to allow the case to be chambered, all you have done is neck size! And then the case will not fit the chamber if already fired a time or two neck sized. Whae keep's the re-sized case from chambering is the shoulder, it must be moved back some little bit to allow the case to once again be chambered. If you do not move it back the case will not chamber. If you do move it back the whole case will be resized to some degree allowing that those case's may only ever fit that rifle again without reversing to resizing per factory spec's. I rifle with excessive head space can be use without a problem by partial sizing and making the case fit the chamber.

**Unclenick** · August 1, 2018, 10:05 AM

J.G. Terry,

So-called bump sizing seems to be just incomplete FL sizing, and that has been done for a long time as a way to work brass less at each reloading cycle to make it last longer. If you don't FL resize all the way, the case doesn't have as much excess headspace to fill in the chamber, so it doesn't stretch as far at the pressure ring during firing. The separate bump term I think came from folks who were trying to neck size in an FL die but got into trouble because the die, being narrower than their chamber, would narrow the brass, elongating it and actually moving the shoulder forward, and then the case wouldn't chamber without effort. So they had to be sure the die shoulder "bumped" into the case shoulder to set it back enough to chamber well.

The difference from neck sizing then is just that you get a narrower case. This can be helpful in that it floats the case so it can find its own center when its shoulder meets the chamber shoulder. It certainly seems to shoot well.

As to the idea a shoulder can be bumped back without having any effect on the case body, I agree with Mr. Guffey that idea is nonsense. Something has to support the sides of the case when the shoulder is set back to any degree, or it will just widen and be hard to chamber.

HiBC · August 1, 2018, 11:09 AM

I understand,and agree,that the term "Headspace" is only correctly applied to the distance from the breech face and whatever feature in the chamber that limits the forward position of the ammunition,be it rim,belt,shoulder,or case mouth.
And I realize the SAAMI or CIP or whatever standards are specified and documented as a dimension between two datums.

Headspace is only correctly applied to the rifle.

I am also fully aware of the term "Head clearance",and,it is my term of choice when talking with people who know what "head clearance" means.

The dimensional fit of ammunition to the rifle is a recurring topic.When a new handloader ,for example,has questions,we have to be able to communicate with useful language. Brevity is good,because the 5 paragraph side trips to the weeds are confusing and exhasperating both to the person asking the question and the person trying to answer the question.

Its been going on for years here,when the term "headspace: comes up an entire choir of experts and critics line up and sing their pet part.

I understand,cartridges do not have headspace.

I challenge anyone to come up with a clear,concise ,explanation of the handloader sizing the brass to fit the chamber that will satisfy the ctitics and meet the needs of the person with the question.

Then lets save it to a sticky and refer people to it.FWIW,the folks who make reloading equiptment refer to "cartridge headspace gauges" and I know what they mean.

For advocates of partial sizing,whether it be to work your brass less or maintain a fireform fit,try this,if you have the trig skills.

Begin with the length that you back off your die.If its 1/4 turn,its about .018.1/2 turn,.036. etc.

Draw a right triangle on a piece of paper.The distance you back off your die is the long leg of the triangle.

Now,go to your chamber drawing and get your case taper angle,or figure taper in thousandths per inch..

If you have 1 deg case taper,or about .0174 per inch,and you back your die off 1/4 turn,you "save" .0003.

For a sense of what .0003 is, try a streak of marker ink on some precision ground steel and pass a .0001 dial indicator over it.

As you size the diameter down,you do lengthen the brass and distend the shoulder.The shoulder is not controlled by the die.

Like squeezing a banana in your fist. That's uncontrolled till you use the die as it was designed and reform the shoulder.

No matter how many years you have been doing it,the "partial sizing" version of neck sizing is a bad idea.

This is not,however,a comment on controlled sizing for a desired head clearance

cw308 · August 1, 2018, 12:15 PM

I enjoy reading this stuff . When I use the term headspace , I know you all know what I'm talking about . Instead of writing bolt face to datum line measurement to me case headspace is easier. I guess I'm like electricity, will take the easiest path. So I will still use headspace sorry , if you know what I mean , don't jump on my back , let's keep on the subject .

USSR · August 1, 2018, 12:29 PM

Quote:

I enjoy reading this stuff . When I use the term headspace , I know you all know what I'm talking about . Instead of writing bolt face to datum line measurement to me case headspace is easier. I guess I'm like electricity, will take the easiest path. So I will still use headspace sorry , if you know what I mean , don't jump on my back , let's keep on the subject .

I know what you mean. Reminds me of the guy who jumps on casters who refer to the rendering of lead products (wheel weights, linotype, etc.) into ingots as "smelting". What people have to realize is, English is an evolving language, with new terms and meanings being added every day. Personally, when I enter a new aspect of reloading or whatever, I learn and use the commonly used nomenclature and never look back. Just MHO.

Don

HiBC · August 1, 2018, 12:38 PM

cw308,I hope you realize we are on the same page.I favor being able to communicate.

Some think the trek into the weeds is more important.

I'm OK with the idea of using correct terminology.

I don't recall seeing the critics offer a succinct ,easily understood answer .

as I said,if someone has such an answer that passes the gauntlet,please post a sticky.

Meanwhile,if anybody asks me if I know of a clip that will feed 45 Long Colts,I'll just smile.I understand.

Then I'll tell him the 44 Mag rim dia is real close to 45 Long Colt rim dia.There might be a chance a Deagle clip could work.

BBarn · August 1, 2018, 12:38 PM

Been loading a variety of rifle rounds for several years using nothing but standard full length die sets. Sometimes I adjust for a full length re-size, but more often just a “partial” re-size for my bolt actions and single shot.

When a finished round chambers and the action closes easily, I know the brass has been sized sufficiently. Perhaps they could have been sized a little less for better case life. Or in some instances they could have been neck sized and produced better accuracy. But I'm getting results good enough to hunt varmints and big game. Things would likely be different if I were competing for group size off a bench rest.

cw308 · August 1, 2018, 01:13 PM

Following instructions on full sizing will work fine and safe in all rifles when all instructions are followed. I only punch paper, so I make adjustments , some good some not so good . Hunting is a different ball game , your rounds have to chamber in all sorts of conditions an shoot fairly accurate . Thanks guys for understanding what I posted .

Some post to show how highly educated they are , that's fine but sometimes it's over my pay grade. I try to keep it simple . The higher ups are there to explain but the have to remember to put it in the simplest terms . I wasn't a chemistry major. Nice talking guys.

Chris

603Country · August 1, 2018, 04:53 PM

In the 40ish years I’ve been reloading, I started with FL sizing. Then I read about partial resizing (neck sizing with my FL die). I switched to that with my 220 Swift and it shot great. Admittedly, the rifle had been set up by a national class gunsmith and a new barrel, so you’d expect it to shoot great. Still, with the tapered case of the 220, I am not sure the case was being resized in any way other than about 2/3 of the neck. Bottom line..it worked great. In later years I tried the Lee Collet Dies, and they worked great, but the cases needed eventual FL sizing, or some degree of FL sizing. I bought Bushing Dies and tried them for a while (they are for sale now). Where I am today is where many folks are. I FL size to the degree to set the shoulder back a touch (a touch being an itty bitty bit). I refer to that approach as “Partial Full Length Resizing”. It puts each case back to the desired size for my rifle. The old style Partial Resizing didn’t do that, nor did the Lee Collet Die, unless you set the shoulder back with a Body Die (which works fine).

cw308 · August 1, 2018, 05:37 PM

603Country
I also tried partial neck sizing , found full length sizing using the Redding Competition shellholder set of 5 worked great , the die is set up to make full contact to the shellholder at the same time sizing the entire neck with minimum headspace ( bolt face to datum line ) the shell holders have different deck heights each .002 lower. Also went with the Redding full & neck S Type bushing dies . They have been in the green box for two years now . Using the standard RCBS full length sizing die , nothing fancy , and its been working great for me . Be Well.

Chris

AVirginian · August 2, 2018, 07:40 AM

Here's my process, for what's worth.

Rifle - Tikka T3 Tactical in 308

Brass - all the same headstamp

After a range trip

Deprime and Neck size using Redding competition die

Check for chamber fit and ease of bolt closing (several rounds)
, if bolt closes easily, finish the rest of the batch, clean and reload.

After subsequent firings, if the bolt begins to require additional effort to close, that batch of brass will be annealed and then neck sized and run through the Redding Body Die. Again chamber checking several to insure proper fit to my rifle. Then clean and reload.

I find that this works the brass as little as possible and it works for me. YMMV

I also like the fact that neck sizing requires far less if any lube as opposed to full length sizing.

Don Fischer · August 2, 2018, 07:59 AM

I believe partial sizing and FL sizing are the same thing it's just that partial sizing fit's the case better to your particular chamber. The entire case is sized when you partial size but the distance to the shoulder may change a bit. No two chambers are exactly the same. A reamer wears as it's used but used again so long as the finish job meets SAMMI spec's. I know this to be true as I have two 243's and both have their own set of dies that stay partial set for that particular chamber. One chamber is just enough bigger than the other to not let the other rifle chamber the round while reloads from the other rifle chamber in both. But I strongly suspect that both chamber's meet spec's. The idea behind the FL die seem's to be to resize any case so that it will fit in any chamber it's made for. They pretty much do that! Partial sizing still FL sizes but fit's the finished case to a particular chamber. It may or may not fit in another chamber.

July 23, 2018, 11:20 AM	#1
AL PALMER Junior Member Join Date: September 5, 2016 Posts: 8	Neck sizing or shoulder bumping What is your thoughts on bumping shoulders or neck sizing. does one give better accuracy over the other? Does neck sizing create bolt problems?

July 23, 2018, 12:13 PM	#3
hounddawg Senior Member Join Date: March 1, 2009 Posts: 4,232	Erik Cortina explains why it is better to FL size and bump the shoulder back a bit. Even if you decide to neck size you will still need to bump the shoulder a bit with a FL resize when the bolt starts to become hard to close http://bulletin.accurateshooter.com/...ze-your-brass/ __________________ “How do I get to the next level?” Well, you get to the next level by being the first one on the range and the last one to leave.” – Jerry Miculek

July 23, 2018, 01:13 PM	#5
T. O'Heir Senior Member Join Date: February 13, 2002 Location: Canada Posts: 12,453	How you size has nothing to do with accuracy. Sizing is about the loaded round fitting in the chamber. Neck sizing is only possible with case that were fired out of the rifle you're loading for. And sooner or later you'll have to FL resize anyway. You're not bumping the shoulder anywhere. You're resizing the case over its whole length. Neither dies nor presses are precise enough to move the shoulders just a few thou either. "...case headspace..." There's no such thing as that. Headspace is a manufacturing tolerance only. __________________ Spelling and grammar count!

July 23, 2018, 01:42 PM	#7
RC20 Senior Member Join Date: April 10, 2008 Location: Alaska Posts: 7,014	AP: Phew, you jumped into the Labrea Tar pit, your bones may be used in a Archaeologic Museum one day. And then there is Mr. Guffey. Welcome to the group. That said its a contentious issue and the simple answer, is, well......... I do minimum shoulder bump regardless of how you express it (ala Mr. Guffy) to keep my cases from cracking at the base. It really is a matter of what suits you. My take was if I had to full size every X rounds I might as well full size as no one agrees 100% on what the accuracy affect is. There are a lot of answers but often not good scientifically proven ones. __________________ Science and Facts are True whether you believe it or not

August 1, 2018, 07:08 AM	#12
J.G. Terry Senior Member Join Date: January 24, 2014 Posts: 577	Hot button topic Bump or neck size is a hot button topic on the net. I'd really like to know. I'm skeptical of partially FL sizing brass. How do I know that only thing done is bumping the shoulder. How do I know this really fits the chamber? What does closing on the case really tell me? Frankly, this shoulder business sounds like voodoo reloading to me. __________________ Intentionally Antagonizing Another MemberInsults and Ad Hominems

July 23, 2018, 12:40 PM	#4
cw308 Senior Member Join Date: September 2, 2010 Location: Plainview , Long Island NY Posts: 3,863	I use to neck size , with neck sizing all the cases aren't really the same length ,you just size the neck until you get resistance on your bolt lift or closing . I switched to full sizing with a case headspace between .001- .002 trim every time after sizing . Every case is as close to exact as possible for me F/L sizing is more accurate then neck . Heavy bolt lifts can cause galling on the bolts locking lugs with zero headspace also . Less wear an tare on the rifle . Hope I helped in some way. Chris

July 23, 2018, 01:41 PM	#6
cw308 Senior Member Join Date: September 2, 2010 Location: Plainview , Long Island NY Posts: 3,863	T I my not know the proper term , headspace , I do want to know the distance from the shoulder to base in the chamber , I full length size my fired cases to fit my chamber with .001 to .002 of room or what ever you call it . As far as my questions , I do like to know what rifle , action , caliber and the OP 's system in sizing , that's just me . Is he loading for hunting or target shooting , two different ball games . Again that's just me .

July 23, 2018, 03:53 PM	#10
craddleshooter Junior member Join Date: March 9, 2018 Location: NY Posts: 90	If your brass is once fired, using a suitable gauge such as the one Hornady has mislabeled their "headspace gauge", first try setting your die to replicate the head to shoulder dimension of once fired brass, (remembering to remove the primer before measuring the fired case). Try a case sized this way in your rifle. If it chambers OK then you are home free. The FL die will size the neck. Is your die one piece, or does take bushings so that necks can be sized differently depending on which bushing is used? In any case, be sure to lube the insides of your necks before sizing and if that lube is some sort of liquid or wax clean it out after sizing so the powder does not stick to it when you charge the cases. A good rule for reloading is to put powder in all of your cases and with them all in the same loading block, with good light. look down into all of them to be sure that they are all filled to the same level, assuming that they are the same load.

July 23, 2018, 05:43 PM	#11
jpx2rk Senior Member Join Date: December 29, 2015 Posts: 387	The only way you or anyone will know is to try doing both and test your ammo.

August 1, 2018, 08:22 AM	#13
cw308 Senior Member Join Date: September 2, 2010 Location: Plainview , Long Island NY Posts: 3,863	J.G.Terry Good question . After reading and kicking things around on this forum to give me a better understanding on what happens to the brass during firing lm comfortable with my system . I full length size every time . My brass was getting shorter after firing from expansion wasn't getting longer . When I full sized the case , the case squeezed down causing the case to become longer , checked with the RCBS Precision Mic . Ordered a Go Gage for my Rem. 700 308 Cal. the gage measures 1.630 bolt closed on the gage with no resistant with a .002 piece of shim on the bolt face the bolt closed with very little resistance , this gave me my chamber length measurement. I ordered the Redding Competition shellholder set of 5 , different deck heights . This allows you to adjust your die off the shellholder without oversizing your brass . I can now size my case length to .0015 to .002 no longer or shorter . If you can strip your bolt , using only the housing , you can slowly size down your case alittle at a time an install the case in your rifles chamber until the bolt closes with very little resistance , that would be your zero case headspace . Hope I Helped in some way , sorry for being so long winded in explaining . Chris

August 1, 2018, 09:25 AM	#14
Don Fischer Senior Member Join Date: March 2, 2017 Posts: 1,868	Neck sizing and this thing called bumping the shoulder is what I've always done with FL dies. Not that long ago I got a set of those Lee collet neck dies and they seem to work great. Neck sizing with a FL dies means nothing more than not allowing the die to reach and move the case shoulder. You can get any where from just a bit down on the case to almost but not quite the shoulder. You can see where the die stopped in the neck of the case. Just two or three loadings and your bolt will no longer chamber the case, it's grown to tight. At that point is where I've set my FL die for years. Trial and error and keep moving the die down and re-sizing the case until the bolt will close easily on it. Lot of guy's want to feel a bit of pressure by not taking the shoulder back quite all the way. When you have done this you have a case sized to fit the chamber of the rifle you sized it for. It may or may not fit in another chamber. Right there I lock the die in place ant it is never used except for that rifle again! I have been one to never keep two rifles in the same chambering but a couple years ago ended up with two 243's, both have their own set of dies. The cartridge's for one of them will not work in the other rifle, can't clost the bolt. Yet the cartridges in the other will fit in both chamber's.have the box's marked to keep the case's seperate. My method of partial sizing I think is what is refereed to as bump sizing sizing. Actually you cannot bump size a case and move the shoulder without sizing the whole case the same amount. Once the case reach's the shoulder, the whole case will be touching the case. Now if the shoulder in your chamber is a bit long, the case being touched should support itself as you continue up. But if you hit the shoulder first I would think that without the case walls to support the case the case would buckle to some extent at the base of the shoulder, possibly keeping the case from chambering. The whole thing is partial sizing. The whole case is partial sized so it will fit one certain chamber. If you have not moved the shoulder enough to allow the case to be chambered, all you have done is neck size! And then the case will not fit the chamber if already fired a time or two neck sized. Whae keep's the re-sized case from chambering is the shoulder, it must be moved back some little bit to allow the case to once again be chambered. If you do not move it back the case will not chamber. If you do move it back the whole case will be resized to some degree allowing that those case's may only ever fit that rifle again without reversing to resizing per factory spec's. I rifle with excessive head space can be use without a problem by partial sizing and making the case fit the chamber.

August 1, 2018, 10:05 AM	#15
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	J.G. Terry, So-called bump sizing seems to be just incomplete FL sizing, and that has been done for a long time as a way to work brass less at each reloading cycle to make it last longer. If you don't FL resize all the way, the case doesn't have as much excess headspace to fill in the chamber, so it doesn't stretch as far at the pressure ring during firing. The separate bump term I think came from folks who were trying to neck size in an FL die but got into trouble because the die, being narrower than their chamber, would narrow the brass, elongating it and actually moving the shoulder forward, and then the case wouldn't chamber without effort. So they had to be sure the die shoulder "bumped" into the case shoulder to set it back enough to chamber well. The difference from neck sizing then is just that you get a narrower case. This can be helpful in that it floats the case so it can find its own center when its shoulder meets the chamber shoulder. It certainly seems to shoot well. As to the idea a shoulder can be bumped back without having any effect on the case body, I agree with Mr. Guffey that idea is nonsense. Something has to support the sides of the case when the shoulder is set back to any degree, or it will just widen and be hard to chamber. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

August 1, 2018, 11:09 AM	#16
HiBC Senior Member Join Date: November 13, 2006 Posts: 8,286	I understand,and agree,that the term "Headspace" is only correctly applied to the distance from the breech face and whatever feature in the chamber that limits the forward position of the ammunition,be it rim,belt,shoulder,or case mouth. And I realize the SAAMI or CIP or whatever standards are specified and documented as a dimension between two datums. Headspace is only correctly applied to the rifle. I am also fully aware of the term "Head clearance",and,it is my term of choice when talking with people who know what "head clearance" means. The dimensional fit of ammunition to the rifle is a recurring topic.When a new handloader ,for example,has questions,we have to be able to communicate with useful language. Brevity is good,because the 5 paragraph side trips to the weeds are confusing and exhasperating both to the person asking the question and the person trying to answer the question. Its been going on for years here,when the term "headspace: comes up an entire choir of experts and critics line up and sing their pet part. I understand,cartridges do not have headspace. I challenge anyone to come up with a clear,concise ,explanation of the handloader sizing the brass to fit the chamber that will satisfy the ctitics and meet the needs of the person with the question. Then lets save it to a sticky and refer people to it.FWIW,the folks who make reloading equiptment refer to "cartridge headspace gauges" and I know what they mean. For advocates of partial sizing,whether it be to work your brass less or maintain a fireform fit,try this,if you have the trig skills. Begin with the length that you back off your die.If its 1/4 turn,its about .018.1/2 turn,.036. etc. Draw a right triangle on a piece of paper.The distance you back off your die is the long leg of the triangle. Now,go to your chamber drawing and get your case taper angle,or figure taper in thousandths per inch.. If you have 1 deg case taper,or about .0174 per inch,and you back your die off 1/4 turn,you "save" .0003. For a sense of what .0003 is, try a streak of marker ink on some precision ground steel and pass a .0001 dial indicator over it. As you size the diameter down,you do lengthen the brass and distend the shoulder.The shoulder is not controlled by the die. Like squeezing a banana in your fist. That's uncontrolled till you use the die as it was designed and reform the shoulder. No matter how many years you have been doing it,the "partial sizing" version of neck sizing is a bad idea. This is not,however,a comment on controlled sizing for a desired head clearance Last edited by HiBC; August 3, 2018 at 08:19 PM.

August 1, 2018, 12:15 PM	#17
cw308 Senior Member Join Date: September 2, 2010 Location: Plainview , Long Island NY Posts: 3,863	I enjoy reading this stuff . When I use the term headspace , I know you all know what I'm talking about . Instead of writing bolt face to datum line measurement to me case headspace is easier. I guess I'm like electricity, will take the easiest path. So I will still use headspace sorry , if you know what I mean , don't jump on my back , let's keep on the subject .

August 1, 2018, 12:38 PM	#19
HiBC Senior Member Join Date: November 13, 2006 Posts: 8,286	cw308,I hope you realize we are on the same page.I favor being able to communicate. Some think the trek into the weeds is more important. I'm OK with the idea of using correct terminology. I don't recall seeing the critics offer a succinct ,easily understood answer . as I said,if someone has such an answer that passes the gauntlet,please post a sticky. Meanwhile,if anybody asks me if I know of a clip that will feed 45 Long Colts,I'll just smile.I understand. Then I'll tell him the 44 Mag rim dia is real close to 45 Long Colt rim dia.There might be a chance a Deagle clip could work. Last edited by HiBC; August 1, 2018 at 12:45 PM.

August 1, 2018, 12:38 PM	#20
BBarn Senior Member Join Date: December 22, 2015 Posts: 887	Been loading a variety of rifle rounds for several years using nothing but standard full length die sets. Sometimes I adjust for a full length re-size, but more often just a “partial” re-size for my bolt actions and single shot. When a finished round chambers and the action closes easily, I know the brass has been sized sufficiently. Perhaps they could have been sized a little less for better case life. Or in some instances they could have been neck sized and produced better accuracy. But I'm getting results good enough to hunt varmints and big game. Things would likely be different if I were competing for group size off a bench rest.

August 1, 2018, 01:13 PM	#21
cw308 Senior Member Join Date: September 2, 2010 Location: Plainview , Long Island NY Posts: 3,863	Following instructions on full sizing will work fine and safe in all rifles when all instructions are followed. I only punch paper, so I make adjustments , some good some not so good . Hunting is a different ball game , your rounds have to chamber in all sorts of conditions an shoot fairly accurate . Thanks guys for understanding what I posted . Some post to show how highly educated they are , that's fine but sometimes it's over my pay grade. I try to keep it simple . The higher ups are there to explain but the have to remember to put it in the simplest terms . I wasn't a chemistry major. Nice talking guys. Chris

August 1, 2018, 04:53 PM	#22
603Country Senior Member Join Date: January 6, 2011 Location: Thornton, Texas Posts: 3,998	In the 40ish years I’ve been reloading, I started with FL sizing. Then I read about partial resizing (neck sizing with my FL die). I switched to that with my 220 Swift and it shot great. Admittedly, the rifle had been set up by a national class gunsmith and a new barrel, so you’d expect it to shoot great. Still, with the tapered case of the 220, I am not sure the case was being resized in any way other than about 2/3 of the neck. Bottom line..it worked great. In later years I tried the Lee Collet Dies, and they worked great, but the cases needed eventual FL sizing, or some degree of FL sizing. I bought Bushing Dies and tried them for a while (they are for sale now). Where I am today is where many folks are. I FL size to the degree to set the shoulder back a touch (a touch being an itty bitty bit). I refer to that approach as “Partial Full Length Resizing”. It puts each case back to the desired size for my rifle. The old style Partial Resizing didn’t do that, nor did the Lee Collet Die, unless you set the shoulder back with a Body Die (which works fine).

August 1, 2018, 05:37 PM	#23
cw308 Senior Member Join Date: September 2, 2010 Location: Plainview , Long Island NY Posts: 3,863	603Country I also tried partial neck sizing , found full length sizing using the Redding Competition shellholder set of 5 worked great , the die is set up to make full contact to the shellholder at the same time sizing the entire neck with minimum headspace ( bolt face to datum line ) the shell holders have different deck heights each .002 lower. Also went with the Redding full & neck S Type bushing dies . They have been in the green box for two years now . Using the standard RCBS full length sizing die , nothing fancy , and its been working great for me . Be Well. Chris

August 2, 2018, 07:40 AM	#24
AVirginian Senior Member Join Date: February 6, 2014 Posts: 128	Here's my process, for what's worth. Rifle - Tikka T3 Tactical in 308 Brass - all the same headstamp After a range trip Deprime and Neck size using Redding competition die Check for chamber fit and ease of bolt closing (several rounds) , if bolt closes easily, finish the rest of the batch, clean and reload. After subsequent firings, if the bolt begins to require additional effort to close, that batch of brass will be annealed and then neck sized and run through the Redding Body Die. Again chamber checking several to insure proper fit to my rifle. Then clean and reload. I find that this works the brass as little as possible and it works for me. YMMV I also like the fact that neck sizing requires far less if any lube as opposed to full length sizing.

August 2, 2018, 07:59 AM	#25
Don Fischer Senior Member Join Date: March 2, 2017 Posts: 1,868	I believe partial sizing and FL sizing are the same thing it's just that partial sizing fit's the case better to your particular chamber. The entire case is sized when you partial size but the distance to the shoulder may change a bit. No two chambers are exactly the same. A reamer wears as it's used but used again so long as the finish job meets SAMMI spec's. I know this to be true as I have two 243's and both have their own set of dies that stay partial set for that particular chamber. One chamber is just enough bigger than the other to not let the other rifle chamber the round while reloads from the other rifle chamber in both. But I strongly suspect that both chamber's meet spec's. The idea behind the FL die seem's to be to resize any case so that it will fit in any chamber it's made for. They pretty much do that! Partial sizing still FL sizes but fit's the finished case to a particular chamber. It may or may not fit in another chamber.