"Bumping" the Shoulder Back

[603Country]

jepp, all my reloading stuff is in my barn workshop, so I'll have a look at the Nosler manual edition in the morning. The info on partial resizing was something that I just assumed that they'd keep in subsequent manuals - though I never looked in later manuals to see. I apologize for telling folks to look where it isn't. Still, the 1/16 gap is what the manual of mine says. The difference between full length sizing and partial sizing is simply that 1/16 of an inch gap between the top of the shell holder and the bottom of the sizing die. You are sizing the case just that little bit less. Really, that's all there is to it. You fire a round in your rifle, which sizes or forms the case to your chamber, then you adjust your die (back it out) enough to cause that small gap (which I set using a feeler gauge), then size that once fired case with the adjusted die set-up. I'd suggest then making up a dummy round to run through the action so that you can feel how the round chambers. If the round is tough to close the bolt on, you'll need to close that 1/16 inch gap a small bit (shrinking the case just a bit) and try again with a dummy round and repeat if necessary, though it probably won't be necessary. I'll still get the Nosler edition number, but what I just outlined is the whole very simple process. The only problem, if you can call it that, is that each round has to be fired in your rifle before you can partial resize it. If you have 200 rounds, you'll be at it for a while. Personally, I usually just load 50 or 60 rounds for each rifle (more for the 223) and reload as needed.

 

[mehavey]

There is no magic "gap" setting. Since the die squeezes that case sides in long before
anything contacts the shoulder, the case/shoulder actually lengthen while the neck is being sized.

You have to slowly adjust the die down while periodically testing in the rifle itself before you
find where the case finally fits... and where you can set/lock the lockring. That setting is
tailored to that rifle's chamber and may be at any gap (in fact it may be all the way down
in tight chambers like my 243.)

 

[mrawesome22]

What mehavey said. I must own all tight chambered rifles cause that partial resizing has never worked for me. The body starts getting squeezed, which pushes the shoulder foward, then they wil not chamber.

Get the Hornady gauges, get a reading from a fired case, adjust die to bump the shoulder .002" below fired case measurement. Done.

 

[Nnobby45]

Okay, I under stand now. It's not so much an accuracy step as it is a life expectantcy precaution.

It's more than that. Neck sized brass will lose it's elasticity after a few firings and not contract enough for easy extraction. FL sizing eliminates that problem.

The objective of "bumping" (or neck sizing) is to leave as little case "rattle-room" as
possible in the chamber after the bolt closes. This minimizes case stretch upon firing,
and maximizes case life before risk of head separation because of brass thinning due
to that repeated stretching (often dramatically)

This is true. The "rattle room" is generally referred to as head space. When the case is fired, the case expands tight against the chamber walls under 50,000 lb. per sq. in. Except for the thick brass near the case head. It can't grip the chamber walls. Under all that pressure, it has to go somewhere, so it stretches back and slams into the bolt face and keeps the primer sealed.

When you size the case, the brass flows forward. The neck grows in length or gets thicker (or both). That brass came from somewher. It came from the stretched case head which grows thinner. Keep firing and sizing and eventually the brass at that point gets so thin you may end up with a crack called a partial case head separation. Mehavey's pic show a FULL BLOWN case head separation which can blow up your gun and YOU.

Therefore, size the case just enough to easily chamber your ammo. This keeps head space to a minimum and slows down case head stretch.

If I've had to trim the brass at the case mouth three times, 4 max., I discard the case and don't risk a case head separation.

 

[CTS]

So, on the last rounds I fired in my .243 I used a Lee collet neck sizing die. I just tried each of them and the bolt closed fine. Is that suitable or would I be better off using the FL die and adjusting it as described above?

 

[mrawesome22]

Very suitable slappy. But after a couple firings the brass will become very hard to chambet and will require that you fl size it.

 

[Nnobby45]

So, on the last rounds I fired in my .243 I used a Lee collet neck sizing die. I just tried each of them and the bolt closed fine. Is that suitable or would I be better off using the FL die and adjusting it as described above?

Neck sizing only works for a while, for the reasons I've already pointed out. If you're going to be a handloader, experiment for yourself. See how long you can get by with neck sizing only before the cases start to stick.

Fred Huntington, from RCBS, once did a demonstration here in Reno for a local sporting good store. He PROPERLY full length sized, loaded, and fired two 30-06 cases. One finally split the case neck after being fired 16 times. The other went a bit longer before the neck split. Split case necks eventually ruined the cases---something that would have happened with neck sizing only.



The subject of this thread is SHOULDER BUMPING, which I define as setting the shoulder back on a case FIRED IN YOUR RIFLE, JUST ENOUGH so the rounds chamber easily. Some like their ammo to chamber with a little "feel". I prefer the bolt to close like nothing's there for hunting ammo. A little feel is ok for target, varmint, and practice.

 

[VTRich]

I've seen Forster sells Bushing Bump Neck Sizer Die that neck size, but also bump the shoulder. Sounds like they are similar to the Redding S bushing dies, only they bump the shoulder also. Has anyone tried these? Or are they just a gimmick?

 

[mrawesome22]

The Forster dies work well.

And yes Redding makes the same thing but dont really mention the bump part. You have to go to their website to read that part.

 

[603Country]

jepp2 and jason, I promised you the Nosler book edition number, and it's the Number 2 in the Nosler series (first reloading book I ever bought). On page 30 they discuss Partial Resizing, and the info is rather brief, and brief enough that I'll just quote it here: " Partial Resizing - This method is a modification of full length resizing. By adjusting the die, most of the case neck is resized while the body of the case is set back only part way. The shoulder is not "worked" and less metal fatigue is induced in this area. Partial resizing should be used only where the case will be fired in the same rifle in which it was fire-formed." On page 31, at the bottom of the paragraphs on Adjusting the Resizing Die, it says "To set the full length resizing die for partial resizing, follow the same procedure (as full length resizing), except that a space of approximately 1/16" should be left between the die and the shell-holder." The Lyman #49 also makes small mention of partial resizing. On page 49, in the left column, about halfway down, it says "Case headspace gauges will allow the reloader to adjust full length resizing dies so that the fired case will be shortened only a minimal amount during the reloading process. This will help prevent case separation failures". Though Lyman doesn't use the term "Partial resizing", that's what they are talking about.

I've been resizing like this since somebody somewhere suggested it years ago. People will tell you that cases will eventually need to be full length resized again in order to chamber, but I really haven't encountered the need to do that. I'm not saying that they are wrong, but only that I haven't had to do that. Now, having said all of the above, I'll say that you could just neck size and accomplish about the same thing and work the brass even less, though in taking the partial resized approach, you don't need a neck sizing die. For target shooting, I'll guess that neck sizing would be preferred. For hunting purposes, I'll go with partial resizing, which will let you tailor the case to feed loose or snug - your choice.

In 40ish years of reloading, I've never had a case head separation, though I've had some split case necks (Norma brass in 220 Swift) after the cases were reloaded probably more than most folks would suggest. And I'll mention that I will occasionally take a case that has been reloaded quite a few times and hacksaw it lengthwise to see what the case looks like on the inside. No problems so far.

 

[old roper]

Fred Huntington, from RCBS, once did a demonstration here in Reno for a local sporting good store. He PROPERLY full length sized, loaded, and fired two 30-06 cases. One finally split the case neck after being fired 16 times. The other went a bit longer before the neck split. Split case necks eventually ruined the cases---something that would have happened with neck sizing only.

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Fred Huntington did a test used 2 Rem case and 2 Win case FL sized after each firing see how long case would last. He use load of 58gr/IMR-4350 with 150gr Speer bullets and rifle used Win Factory 30-06 rifle.

Rem case #1 neck split at 36th firing and FL sizing
Rem case #2 neck split at 52nd firing and FL szing

Win case #1 neck split at 50th firing and FL sizing
Win case #2 neck split at 55th firing and FL sizing

All cases split after firing none during FL sizing

If you have a copy of PO Ackley Handbook for Shooters & Reloaders Vol II page 78/79 has full article on the above test.

When I started loading mid 60's I FL sized every time never used neck die and I got over 10 firing per case and I did some partial sizing.

 

[jason75979]

jepp2 and jason, I promised you the Nosler book edition number, and it's the Number 2 in the Nosler series (first reloading book I ever bought). On page 30 they discuss Partial Resizing, and the info is rather brief, and brief enough that I'll just quote it here: " Partial Resizing - This method is a modification of full length resizing. By adjusting the die, most of the case neck is resized while the body of the case is set back only part way. The shoulder is not "worked" and less metal fatigue is induced in this area. Partial resizing should be used only where the case will be fired in the same rifle in which it was fire-formed." On page 31, at the bottom of the paragraphs on Adjusting the Resizing Die, it says "To set the full length resizing die for partial resizing, follow the same procedure (as full length resizing), except that a space of approximately 1/16" should be left between the die and the shell-holder." The Lyman #49 also makes small mention of partial resizing. On page 49, in the left column, about halfway down, it says "Case headspace gauges will allow the reloader to adjust full length resizing dies so that the fired case will be shortened only a minimal amount during the reloading process. This will help prevent case separation failures". Though Lyman doesn't use the term "Partial resizing", that's what they are talking about.

I've been resizing like this since somebody somewhere suggested it years ago. People will tell you that cases will eventually need to be full length resized again in order to chamber, but I really haven't encountered the need to do that. I'm not saying that they are wrong, but only that I haven't had to do that. Now, having said all of the above, I'll say that you could just neck size and accomplish about the same thing and work the brass even less, though in taking the partial resized approach, you don't need a neck sizing die. For target shooting, I'll guess that neck sizing would be preferred. For hunting purposes, I'll go with partial resizing, which will let you tailor the case to feed loose or snug - your choice.

In 40ish years of reloading, I've never had a case head separation, though I've had some split case necks (Norma brass in 220 Swift) after the cases were reloaded probably more than most folks would suggest. And I'll mention that I will occasionally take a case that has been reloaded quite a few times and hacksaw it lengthwise to see what the case looks like on the inside. No problems so far.

Yes sir, I found it in my Nosler manual.

I will give it a shot over the holidays with empty brass to be on the safe side. Thanks everyone for the responses.

 

[mehavey]

I recommend not starting w/ the "1/16th" trick as printed above.
Simply adjust the die until the case just fits the chamber and lock it (-- wherever that is.

As to split necks, I anneal after 6-12 reloadings (or when the expander ball starts to "squeak" -- whichever is sooner). That resolves the split neck problem AND keeps neck tension uniform..

 

[603Country]

mehavey, as you mentioned, the thickness of a dime (or 1/16") isn't a magic distance, but that is where I usually start with a new rifle since I have to start somewhere. For my 270 and my 220, it was just right, but for the 223 it wasn't enough. For the 260 it was just a bit too much.

Now that I had to find the books and the specific sections on partial resizing, I found in one of the books that cases with very little body taper don't take to partial resizing as well. They used the 243 case as an example, and I'll suppose that would include my 260 as well. That may explain why my partial resizing of the 260 cases hasn't resulted in cases that are as snug in the chamber as I like. And I think I remember somebody in this long discussion mentioning that it didn't work on his 243. Maybe that's why.

 

[mehavey]

Thinking about it, you're probably right.

I just start w/ the die 3/4 turn out -- which with a 14 pitch thread is
(1/14)*.75 ~ 1/18th inch

Great minds, don'cha know.....



.

 

[amamnn]

To clear up a few details about bumping and the various Redding and Forster and Lee dies mentioned.

1-- A neck sizing die does not size anything but the neck. If bushings are used you have exact control over how much the neck diameter is reduced. Collets, as used in the Lee dies are less exact.

2-- A full length sizer sizes neck, shoulder/base length and body

3-- The Redding "S" die is a FL sizing die which allows you to select the exact amount of neck reduction via the use of bushings.

4-- The Redding body bump die is essentially a FL die that leaves the neck untouched.

5-- The Forster neck bump die is essentially a bushing type neck die which can also be set to bump back the shoulder.



The differences might seem confusing to beginners, but there really is a use for and a difference in them all.

 

[Nnobby45]

I've seen Forster sells Bushing Bump Neck Sizer Die that neck size, but also bump the shoulder. Sounds like they are similar to the Redding S bushing dies, only they bump the shoulder also. Has anyone tried these? Or are they just a gimmick?

Remember that the purpose of the bushing die is to be able to size case necks of varying thicknesses from one mgfr. to the next. It also saves case necks, because they're only sized--not popped back out, over working the brass and possibly pulling the neck out of alignment.


Standard dies size down more than necessary and the expander pops the neck back out for consistent bullet tension no matter what the brass thickness. The outside diameter varies with brass thickness, the inside diameter is consistent.

With bushing dies, the outside diameter is consistent and the inside diameter varies with brass thickness. That's why proper bushing selection is necessary for consistent inside diameter.

Figure the case neck thickness times 2 plus bullet diameter and thats the neck diameter of the loaded round. The diameter less than that (of the sized case), expressed in thousandths, is the bullet tension.

EXAMPLE: .013 X2 = .026 plus .308 = .334
for .003 tension, you'd select your .331 bushing

Use that same bushing for brass that's .011 that's .022 + .308 = .330 and your bushing would be too big to size the case neck at all. You'd need a .327 bushing. Or the appropriate one for the tension you want.





Target ammo single loaded in a bolt action rifle, works fine @ .0015 to .002. Hunting ammo that feeds from the magazine could use more. About .003 to .004. Some factory ammo could be considerably more.

On the other hand, I bought some Nosler Premium Brass, all sized and prepped, and it's only .0015 less than loaded round diameter. It's designed for hunting.

 

[F. Guffey]

I suppose it is possible to talk it to death I choose to not allow this stuff to not lock me up, first I have a chamber, the chamber is in the rifle, the chamber is stable, the chamber is not adjustable unless the chamber is some kind of Savage, even then when the chamber is adjustable reloaders can not form cases to fit without fire forming. example-6mmBR shooter grease their ammo, yes, they become slide and glide shooters. Makes me thing Savage shooters adjust the barrel for busy work.

My presses and dies are adjustable, both have threads. Adjustable from and or to? My dies are adjustable in the press from the shell holder or to the shell holder, the length of the case from the head of the case to it’s shoulder is controlled by the gap or lack of gap between the die and shell holder, as it is said in poker, “Study long, Study wrong”, I do not make wild guestimates of adjustments in fractional turns or degrees, I go straight to the standard/transfer tool, the feeler gage, the companion tool to the press, the feeler gage (Redding calls it a thickness gage).

Back to the chamber, it is not adjustable, the case length is adjustable, and this stuff does not lock me up, I adjust the press, die and shell holder to control the length of the case first, I off set the length of the chamber with the length of the case from the case head to it’s shoulder, I use the case length to off set the length of the chamber from the face of the bolt to the shoulder of the chamber.

Again, I have one rifle with .016 thousands head space, not easy to get the shoulder forward .016 thousands to off set the field reject length + chamber, unless I purchase cases that have been fired in trashy old chambers, THEN!!! it is important to be able to determine which trashy old chamber the case was fired in, then there is the 280 Remington case, the 280 Remington is a ‘can not miss’ when off setting head space for a ‘rattle room’ 30/06 chamber, unless you are a bumper wild guestimate of an adjuster reloader, in that situation it is possible to get lucky, luck does not bring about repeatable, and that is the reason I use the feeler gage when setting up my die to shell holder in the press.

And, NO, it is not necessary to use the 280 Remington cases, again, I want to know the length of the chamber before I fire, not after, I want to know how to adjust the die to the shell holder when sizing cases to off set head space or the length of the chamber from the bolt face to the shoulder of the chamber.

There are tools for sell, for the most part I can match the accuracy of expensive tools with the feeler gage, I did not say I do not have expensive tools. For those that push expensive tools prefer to fire first then determine the effect the chamber had of the case when fired, I determine the effect the chamber will have on the case when fired. Then with other home made tools I verify the effect the chamber had on the case when fired, and as a results, I cut down on all that case travel.

F. Guffey

 

[F. Guffey]

and 1/16th of .071 thousands (= to 1/16 turn of the die with 14 threads per inch) is= to a gap of .0044, again, why make the wild guestimate of a turn in degrees or fractional turns when verifying can be done with a feeler gage.

Again, this stuff does not lock me up or hang me up, I am familiar with transfers, standards and verify, there are some talented reloaders that use a light on the back side of the die and shell holder, just an opinion but, that has bot to take practice.

Back to the .0044 (1/16th of a guestimate), In the perfect world is a good place to start if the relaoder understood minimum length = full length sizing and if the reloader had a perfect go-gage length chamber and were not trying to size 6 time fired cases, the .0044 gap would be the perfect place to start. then there is the advantage of ‘time is a factor’.

F, Guffey

 

[Bart B.]

I'm a bit surprised nobody's mentioned using a case headspace gage such as the RCBS Precision Mic. This measures the case headspace (shoulder datum point back to the case head).

1. Take a fired case then measure its headspace with the gage.

2. Then full length size that case.

3. Measure its headspace. If the die is set perfectly, the sized case will have a headspace 2 to 3 thousandths shorter than it was. Lock the die ring in place. If the sized case shoulder's set back more or less than this, go on to step 4.

4. If the case headspace is too short, trash the case. Then back out the die a very tiny amount and repeat these steps with another fired case. If it's still too long, screw the die down a very tiny bit, then start over at step 1. 1/10th inch radially on the thread turning moves the die about 1/1000th of an inch.

5. The case is now full length sized correctly for your rifle. Get another fired case and start over.

Top competitive shooters have learned that fired cases full length sized such that their shoulder's set back 2 to 3 thousandths is about perfect. Never ever should the case bind in the chamber when the bolt's closed because if the bolt binds (your feel it's a tiny bit hard to close), the bolt body and head won't be at the same place for each shot; especially if the bolt face isn't squared up with the chamber axis.

Guffey's procedure do the same thing, but I think it's easier with a case gage.

You can also get shell holders from Redding in different heights. Use the one that when the die just touches it when the full length sizing die sets the fired case shoulder back 2 to 3 thousandths. Using this method, your cases may have a more uniform headspace after full length sizing.

Three cheers for full length sizing anyway, the most accurate rifles I know of shoot that way with full length sized cases.