What is going on here with my necks

[whatsupdoc]

So I typically FL size my 6.5 Creed brass then push a mandrel through the neck.

I am using a custom neck honed (.2885) Forster die and a Brownells mandrel setup. I had some issues with seating depth variation so I checked the necks with a pin gauge and found that the .2620 pin would fit nicely in the neck but would get tight or stop at the shoulder neck junction.

The brass was Lapua with over 30 firings on it. So I ream the necks and everything is good.

I then resize some 5x fired Hornady brass and check with the pin gauge and sure enough same issue.
I replace the old mandrel with a new one and now the cases are all good so I assumed the mandrel was worn out.

So I take both mandrels mark four identical spots on them and take measurements with TWO digital micrometers one standard and one blade, both resolve to .0001 and both mandrels measure the same

OLD NEW
.2630 .2629
.2629 .2629
.2629 .2629
.2629 .2629

What The Heck is going on.

 

[JSH]

Sounds like donut

 

[243winxb]

? https://www.ampannealing.com/articles/42/annealing-under-the-microscope/

Looks like a donut may come with new brass?

A bushing die doesnt size the area at the neck/shoulder junction. Edit/add- The donut would not be an issue if using a bushing.

 

[BeefyT11]

Since your using a fl die and a mandrel it sounds like the mandrel that wasnt working, for one reason or another wasn't sizing the neck in it entire length... was the cap on tight enough the first time when it wasn't sizing enough? If it wasn't the mandrel would be allowed to move up in the die. Is the older mandrel shorter than the new mandrel? Leading to it not sizing as far down the neck. If you put the old mandrel in and turn the die down a turn or 2 does your problem go away again?

 

[mikecr]

Sounds like the only change here is of running mandrels through the Hornady necks twice.
If your die is FL sizing the necks, you should probably stop doing that anyway.
If so, you're just bringing donut area into tension, which will never be a 'good' thing.

 

[whatsupdoc]

Couple of things, Not a bushing die.
Mandrel was definitely going in deep enough.
I did not need to push the mandrel through twice on the Hornady brass. The old mandrel left a "donut" the new mandrel did not.

 

[searcher]

When you run that mandrel down the neck and extract it, the neck closes back in a bit. This is more pronounced over time as the necks harden through firings. With 30 firings on the cases - you most likely have nasty doughnuts that don't cooperate with your mandrel. The pin gauges will give you a different reading at different depths as brass just never seems to flow to the same stop points due to slight differences in how much one may have cut into the neck if the brass is neck turned, whether the necks were all annealed exactly the same (near impossible), whether the bullets had been seated at the exact same seating depth, bullets all exactly the same length, etc, etc. There are usually several factors at work to make minute differences in how the doughnuts progress. Annealing and running the mandrel through a few times works to some degree, especially if followed with a light neck turn to take some of the doughnut off from the outside. Better option IMO opinion is an inside neck cutter. If you don't turn necks and using factory die - best to use inside cutter. Because you need to get the right sized cutter and pays to get a good tool to mount it in like a Wilson trimmer, it will be less expensive to buy new brass and call it a day. The more you get into shooting - the more you will appreciate having had these tools if you don't already own them, though. The cutter and Wilson trimmer probably go for somewhere in the neighborhood of $200.00 - maybe less. Then you might get another 20 or 30 firings on the brass. Good luck!

 

[dgeesaman]

So I typically FL size my 6.5 Creed brass then push a mandrel through the neck.

I am using a custom neck honed (.2885) Forster die and a Brownells mandrel setup. I had some issues with seating depth variation so I checked the necks with a pin gauge and found that the .2620 pin would fit nicely in the neck but would get tight or stop at the shoulder neck junction.

The brass was Lapua with over 30 firings on it. So I ream the necks and everything is good.

I then resize some 5x fired Hornady brass and check with the pin gauge and sure enough same issue.
I replace the old mandrel with a new one and now the cases are all good so I assumed the mandrel was worn out.

So I take both mandrels mark four identical spots on them and take measurements with TWO digital micrometers one standard and one blade, both resolve to .0001 and both mandrels measure the same

OLD NEW
.2630 .2629
.2629 .2629
.2629 .2629
.2629 .2629

What The Heck is going on.

Donut or not, the shoulder significantly stiffens the brass at the base of the neck and so it ends up at a different relaxed ID.

Does your bullet run in that deep? I hope not.

David

 

[whatsupdoc]

In a gas gun the mag length makes it necessary to load 140's deep.

 

[243winxb]

Gas Gun- so not a tight neck chamber, where a donut would be a pressure problem.

Donut may provide more neck tension/bullet pull. Not a bad thing if loading from a magazine. No bullet movement when the round chambers.

I guess only the target knows if a donut is a problem.

 

[mikecr]

Donuts are never useful.
The answer is to stop FL sizing necks.

 

[Webster]

So I typically FL size my 6.5 Creed brass then push a mandrel through the neck.

I am using a custom neck honed (.2885) Forster die and a Brownells mandrel setup. I had some issues with seating depth variation so I checked the necks with a pin gauge and found that the .2620 pin would fit nicely in the neck but would get tight or stop at the shoulder neck junction.

The brass was Lapua with over 30 firings on it. So I ream the necks and everything is good.

I then resize some 5x fired Hornady brass and check with the pin gauge and sure enough same issue.
I replace the old mandrel with a new one and now the cases are all good so I assumed the mandrel was worn out.

So I take both mandrels mark four identical spots on them and take measurements with TWO digital micrometers one standard and one blade, both resolve to .0001 and both mandrels measure the same

OLD NEW
.2630 .2629
.2629 .2629
.2629 .2629
.2629 .2629

What The Heck is going on.

It isn't reasonable that a hardened steel mandrel will wear out on brass. Are the mandrels hardened or soft steel? The best micrometers are not accurate to 0.0001". They may be +- 0.001" To lazy to look it up. Don't understand why a reamer would fix it and a mandrel maybe 0.0001" bigger would fix it. Reaming takes the donut out which must be bigger than 0.001" and a mandrel 0.0001" bigger with springback fixes it? I never shot competition but I shoot groups under .350" all the time with a varmint rifle. A few times a year I shoot a group in the 1's and 5-10 under .250". Never sorted bullets, primers, cases. Never used a mandrel. Redding FL bushing die (6BR) or a Whitten FL bushing die (6BRX). I think I got a barrel that deserves to be on a better rifle.

 

[Webster]

? View attachment 1173242 https://www.ampannealing.com/articles/42/annealing-under-the-microscope/

Looks like a donut may come with new brass?

A bushing die doesnt size the area at the neck/shoulder junction. Edit/add- The donut would not be an issue if using a bushing.

10 um = 0.00039". I don't think I would call a 1/2 thou a donut?

 

[Hohn]

It isn't reasonable that a hardened steel mandrel will wear out on brass. Are the mandrels hardened or soft steel? The best micrometers are not accurate to 0.0001". They may be +- 0.001" To lazy to look it up. Don't understand why a reamer would fix it and a mandrel maybe 0.0001" bigger would fix it. Reaming takes the donut out which must be bigger than 0.001" and a mandrel 0.0001" bigger with springback fixes it? I never shot competition but I shoot groups under .350" all the time with a varmint rifle. A few times a year I shoot a group in the 1's and 5-10 under .250". Never sorted bullets, primers, cases. Never used a mandrel. Redding FL bushing die (6BR) or a Whitten FL bushing die (6BRX). I think I got a barrel that deserves to be on a better rifle.

"

Micrometer accuracy varies a bit with the size range, but almost every modern 0"-1" micrometer be be absolutely accurate within 0.00015". A caliper is the tool for mere thousandths. Micrometers are for tenths and-- in some cases-- a bit better.

I present to you a micrometer accurate to +/- *half a micron*: That would be plus or minus 0.000019685"

https://www.mitutoyo.com/press_releases/high-accuracy-digimatic-digital-micrometer/

 

[Hohn]

So I typically FL size my 6.5 Creed brass then push a mandrel through the neck.

I am using a custom neck honed (.2885) Forster die and a Brownells mandrel setup. I had some issues with seating depth variation so I checked the necks with a pin gauge and found that the .2620 pin would fit nicely in the neck but would get tight or stop at the shoulder neck junction.

The brass was Lapua with over 30 firings on it. So I ream the necks and everything is good.

I then resize some 5x fired Hornady brass and check with the pin gauge and sure enough same issue.
I replace the old mandrel with a new one and now the cases are all good so I assumed the mandrel was worn out.

So I take both mandrels mark four identical spots on them and take measurements with TWO digital micrometers one standard and one blade, both resolve to .0001 and both mandrels measure the same

OLD NEW
.2630 .2629
.2629 .2629
.2629 .2629
.2629 .2629

What The Heck is going on.

Your data clearly shows that the mandrels are no different and not worn.

A donut in 30x fired brass is not a defect or a problem-- it is inevitable. Congrats on such great case life.

The root of your issue with the Hornady brass is that you apparently repeated the same process and got different results. You thought it was a different process because of the different mandrel, but it ended up being the same process.

So there are only two possibilities. One, the "Same process" wasn't actually the same in that there was another variable even if the mandrels were the same, somehow the process still differed. Two, the output of the process is within the expected variation and it's not actually a different output. I've found it helpful to formalize investigation items using a Fault Tree. You might want to do something like this and add sources of variation and things to rule out.

 

[dgeesaman]

"

Micrometer accuracy varies a bit with the size range, but almost every modern 0"-1" micrometer be be absolutely accurate within 0.00015". A caliper is the tool for mere thousandths. Micrometers are for tenths and-- in some cases-- a bit better.

I present to you a micrometer accurate to +/- *half a micron*: That would be plus or minus 0.000019685"

https://www.mitutoyo.com/press_releases/high-accuracy-digimatic-digital-micrometer/

It was hard for me to look past that too.

as a general rule of thumb, quality dial calipers guarantee .001 accuracy and usually perform .0005”.

Outside micrometers can do .0001 or better in some cases.

Inside micrometers vary but I have a nice digital model for 6-8mm bores that is accurate within .00016”. Based on playing with a ring gauge it’s better than that.

Based on the performance of that inside mic I might upgrade my outside mics to a digital model that resolves to the .00005”.

Back to regularly scheduled donut arguments.

 

[Webster]

"

Micrometer accuracy varies a bit with the size range, but almost every modern 0"-1" micrometer be be absolutely accurate within 0.00015". A caliper is the tool for mere thousandths. Micrometers are for tenths and-- in some cases-- a bit better.

I present to you a micrometer accurate to +/- *half a micron*: That would be plus or minus 0.000019685"

https://www.mitutoyo.com/press_releases/high-accuracy-digimatic-digital-micrometer/

I guess I wasn't up to date on micrometers. To be accurate it takes a little skill to use them. Where I worked ten years ago we were not allowed to use a micrometer unless it was certified and had a certified dated sticker on it. Digital micrometers can range from around $100 to $1500. Do we really need to measure things that accurate?

 

[dgeesaman]

I guess I wasn't up to date on micrometers. To be accurate it takes a little skill to use them. Where I worked ten years ago we were not allowed to use a micrometer unless it was certified and had a certified dated sticker on it. Digital micrometers can range from around $100 to $1500. Do we really need to measure things that accurate?

The digital ones take less skill because you don't need to read the last digit with a Vernier marking. That said, the measurement is easily affected by things like a warm hand on the micrometer frame, deflection of the piece, and alignment of the tool. Digital is definitely better for me because I can take 5 readings in the time it takes me to read a standard twice.

As for accuracy, we don't need micron accuracy for very many things. Sorting bullets by diameter? Use a digital micrometer with sub-.0001" accuracy. Measuring to an ogive? Calipers will work. Measuring your sizing bushings? Inside bore micrometer. Measuring your sized brass? Micrometer with .0005" accuracy is enough. Checking primer pockets for expansion? Inside points on your dial caliper. IMHO.

 

[whatsupdoc]

LOL, lets get past the micrometers (I checked with 2 different mics) both are accurate to .0001 and before I used them I confirmed by checking a couple of pin gauges. One is a Mitutoyo the other is a SPI.


I definitely appreciate all the suggestions, more brains the better.
The only thing I forgot to mention is that I anneal every firing, I dont think it has any bearing.
Realizing that other than my 223 the other calibers I load most bullets never get the base to or past the neck shoulder junction.