Thread: Case lengthening when bump sizing

I agree Eben there are other reasons why a case won't chamber, but the OP was referencing the relationship between shoulder and neck rather than any of the other dimensions. I assumed it was a given in his scenario that all other factors are correct, so we are off on a tangent from the OP.
In saying that, I am still not sure I understand the OP's original question, in which case I was on a tangent already..

Originally Posted by -BW-

4. Sizing can happen 2 ways, full length, or neck only. The terminology of 'bump sizing' is somewhat misleading, as it is nothing more than full length sizing but only just enough to bring the shoulder within spec of the rifles chamber, but not all the way down to the shellholder. It seems some people do this with or without the expander ball fitted. Correct me if I'm wrong here but this is as I understand it.

True shoulder bump sizing as it is used in benchrest and target reloading does not use a FL die (unless the neck portion has been reamed out, making it a body die).

What you are describing above (FL die screwed down only far enough to bump the shoulder) would still size a portion of the neck. Measure the neck OD or ID before and after sizing to confirm this.

True bump dies do not touch the neck at all. The diameter of the neck is the same after (shoulder and body) sizing.

My primary concern during reloading is to work the neck as little as possible. Neck tension is the holy grail w.r.t accuracy, and I do everything I can to get consistent neck tension.

What I do is this:
Body die to push the shoulder back (but not touch the neck)
Collet die to size the neck (in as concentric a way as possible)

Or you could combine both operations into one by using a bushing bump die with appropriate bushing to give you the neck tension you require.

Both these methods do not use an expander ball, so the neck is never stretched beyond the fired dimension.

reinventing the wheel..I shall take photo and shall give reference to where this came from...hold the line caller...

Nosler reloading manual number #2 1981 publication..... this particular manual is great as the front half has really good details on HOW reloading works...not just load data... for brains like mine this is gold...to understand how stuff works and in what order means it sinks in .
partial length resize goes to stage #3 full length resize goes to stage #4 take note of web area of case..not touched. also see tiny gap at shoulder area,also not touched..in text below image 1/16th" is used as how big that gap is......

When I was younger and more stupid than I am now, I had a thing about case length so set out to find my rifles max case lenght, and it was 4 thou longer than the stated lenght in that slopey chamber 2.015 is the max stated overall lenght but mine was 2..019 Basiacally meant I didn't trim until; I reach 2.2.017 ish. For this rifle those worries are long gone shot a heap of rounds & everything is moving out, still shoots really well. Just measured it for shit & giggles 2.047

Originally Posted by -BW-

I agree Eben there are other reasons why a case won't chamber, but the OP was referencing the relationship between shoulder and neck rather than any of the other dimensions. I assumed it was a given in his scenario that all other factors are correct, so we are off on a tangent from the OP.
In saying that, I am still not sure I understand the OP's original question, in which case I was on a tangent already..

.
I was referencing head to shoulder increases .

Originally Posted by Micky Duck

Attachment 217894

Thanks for posting that , though personally I'm not convinced that depiction is completely accurate as the case goes from no contact to perfect fit in one step . The books are on occasion wrong , for example in one of the Hornady manuals, they show the datum point to be at the base of the neck as apposed to it being mid shoulder. If your a bit mean with the lube , cases will often bare witness marks where it has started engaging the die way before the neck would even have start to be sized . Again, just my opinion based on my experiences .

So before this goes a lot further, please don't let this become an argument, my post is to encourage debate and discussion .

I have witnessed the case lengthening , measured at the shoulder using a comparator . So nobody will convince me I'm wrong on that account it can and does happen and has caused an few others some issues . The explanation I've given is the opinions of others as well as my own . The cause is really the point for discussion .

I've said this before , "I never mind being proven wrong in fact I'm used to it , I'm married! " But , so far nobody has put forward a compelling counter theory to convince me that I am wrong in my belief of the cause .

Rcbs came up with the X dies in the early 2000 to kind of overcome the problem of case lengthening.
I beleive the lengthening happens when the olive is pulled out from the neck.
Hence why some remove the olive spindle, do a full or partial length resize and use an expander after to standardise internal neck dimensions.

Although the shape of the case could lead to more or less brass flow forward.
Compare a 30-30 or a 22 hornet versus an ackley improved chambering .

If you have a large chamber then it is possible for the shoulder to move forward if "partially full length sizing"
As the case body is sized inward but the die isn't low enough yet to contact the shoulder it moves forward.
This can cause tight chambering on the shoulder...the solution is obviously to lower the die or change shell holder untill the shoulder is bumped back a couple of thou.

Anytime you squeeze a brass cylinder down in diameter without holding the top from growing it will grow lengthwise.

Originally Posted by ebf

True shoulder bump sizing as it is used in benchrest and target reloading does not use a FL die (unless the neck portion has been reamed out, making it a body die).

What you are describing above (FL die screwed down only far enough to bump the shoulder) would still size a portion of the neck. Measure the neck OD or ID before and after sizing to confirm this.

True bump dies do not touch the neck at all. The diameter of the neck is the same after (shoulder and body) sizing.

My primary concern during reloading is to work the neck as little as possible. Neck tension is the holy grail w.r.t accuracy, and I do everything I can to get consistent neck tension.

What I do is this:
Body die to push the shoulder back (but not touch the neck)
Collet die to size the neck (in as concentric a way as possible)

Or you could combine both operations into one by using a bushing bump die with appropriate bushing to give you the neck tension you require.

Both these methods do not use an expander ball, so the neck is never stretched beyond the fired dimension.

You can avoid one of your steps by annealing and taking out your expander. Simple. Never had any issue with neck tension after proper annealing. There is plenty of nonsensical rubbish that you need a certain very expensive machine to properly anneal. Best you tell that manufacturer to read about the Houston boys. Without the expander and properly annealed brass your neck is sized correctly because it is squeezed during proper sizing.If your die is sizing the body of the brass it must logically be sizing the neck. Why they invented the expander now stumps me. The only logiacl explanation is that dies were designed before the effects of proper annealing of brass was understood. My 2C. Bullet seating is easily aided by chamfering the inside of the neck.

Okay , so I apologise for not knowing how to post a link , I'm a technophobe .

I found a perfect demonstration on YouTube, the video was posted by "primalrights" and called " Setting Up a Sizing Die ". To help I've written it as is , on YouTube. To save time , because the video is quite long , watch from 26 minutes and 25 seconds to 27 minutes and 30 seconds .

Guys, if you have a spare couple of minutes find and watch this and share your thoughts .

Regards all

Originally Posted by TeRei

You can avoid one of your steps by annealing and taking out your expander. Simple. Never had any issue with neck tension after proper annealing.

TeRei, it depends on what brand of dies you are using. Some FL dies without an expander would squeeze the neck down so much that the case becomes useless.

I'll repeat my mantra : MEASURE.

The best way to see what a die is actually doing to a case is to measure dimensions before and after.

Originally Posted by ebf

TeRei, it depends on what brand of dies you are using. Some FL dies without an expander would squeeze the neck down so much that the case becomes useless.

I'll repeat my mantra : MEASURE.

The best way to see what a die is actually doing to a case is to measure dimensions before and after.

The best dies. They came in green and are in a strange metal contraption called a T7.

Originally Posted by TeRei

The best dies. They came in green and are in a strange metal contraption called a T7.

You have much to learn Padawan

Originally Posted by veitnamcam

If you have a large chamber then it is possible for the shoulder to move forward if "partially full length sizing"
As the case body is sized inward but the die isn't low enough yet to contact the shoulder it moves forward.
This can cause tight chambering on the shoulder...the solution is obviously to lower the die or change shell holder untill the shoulder is bumped back a couple of thou.

Anytime you squeeze a brass cylinder down in diameter without holding the top from growing it will grow lengthwise.

Totally agree on how as the body is sized the case lengthens .��

I'm trying to get a few of the doubters to watch the YouTube video I've listed in #26 .

@Micky Duck , has the video convinced you ? ��