Mandrel size help

[NJRaised]

Running .223 rem with 75 elds.

On a loaded round , outside neck diameter is .248”.

After sizing (.247” bushing), my outside neck diameter is .246”. Then I run a .223” (actually measured at .223”) mandrel. The outside neck diameter is then .247”, but if I measure the inside neck diameter, I have .222”.

Is this considered .001 or .002” neck tension? Bullet diameter is .224.

Any suggestions?
Starline brass, annealed every firing.

 

[918v]

If you are measuring the ID with your caliper then that explains the discrepancy. Use a plug gauge. In my opinion you have .001” neck tension being you’re using a .223” mandrel.

 

[RegionRat]

but if I measure the inside neck diameter, I have .222”.

Is this considered .001 or .002” neck tension? Bullet diameter is .224.

Forums can be arbitrary. "Neck Tension" is generally equal to Bullet to Neck Interference.

When you subtract the neck ID from the bullet diameter, so 0.224 bullet - 0.222 neck ID = 0.002" NT

This is defined this way because different brass hardness conditions and wall thickness would mean very different outcomes are possible with a given neck OD and bushing. Discussing the net interference makes it a value that bypasses those other variables.

Bushings have often been found to be different than their markings. Many folks have no way to know what their brass condition is, so the result on the ID size isn't predictable from the brass dimensions and bushing size.

We bypass all that by defining NT as the resultant net interference between the bullet and the brass, and even then we do not pretend it means we would know the seating force. YMMV

 

[Baron23]

If you are measuring the ID with your caliper then that explains the discrepancy. Use a plug gauge. In my opinion you have .001” neck tension being you’re using a .223” mandrel.

This....either an inside micrometer (hard to find for our small distances and expensive) or buy a few pin gauges. I have not found that I can get high accuracy/consistent I.D. measurements with a caliper but maybe that's just my lack of skills.

Just my thoughts but I find pin gauges to be easy to use and very helpful is absolutely determining the degree of interference fit between case and bullet.

Class ZZ Pin Gages | Travers Tool

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[Rob01]

Any suggestions?

Toss the mandrel and load your ammo.

 

[RegionRat]

A coarse set of basic pin gages for rough tasks and general work is not expensive.

Using pins to measure the ID of small holes is much better than trying to use caliper jaws.

You can sometimes find very good ones on surplus auction web sites that would be sold for pennies on the dollar and worth the time to snag them.

As a hobby reloader, you don't need the same level of tools/gages that a labs would use, you could really improve your process with inexpensive pins in 0.001" steps and still learn to judge the feel and fit of these pins without going down the the tenths.

Even the cost of inline dies and arbor presses with force packs is within reach of folks want to improve their brass prep game.

With the force-pack feedback, and knowledge of the neck ID, you may even just keep these things temporarily and sell them off later once your process is stable and you know what you are doing.

Folks generally build their tool sets and skills over time and keep things like inline dies, arbor presses, pins, etc. because someday they may plan to add a different cartridge to their stable and will want to cut the learning loop quick. YMMV

Good Luck.

 

[memilanuk]

This....either an inside micrometer (hard to find for our small distances and expensive)

There's another option...

 

[matt33]

I use an inside the neck sizing mandrel for autoloaders. I size the neck .003" under bullet diameter for AR platform rifles and have had great luck with these:
https://21stcenturyinnovation.com/buy-online/ols/products/caliber-specific-expander-mandrel

There are too many variations in neck wall thickness for me to be comfortable using bushing dies. Neck tension is only as good as the consistency of brass case wall thickness with the bushings. The mandrel dies that are similar in style to what I posted are a much better choice IMHO.

 

[Baron23]

There's another option...

Oh cool...didn't know those existed. I personally still like pin gauges as you can't cock them or anything. It fits or it don't fit. They come...well, in all sizes but the ones I linked are in .0005 (five 10,00ths, right) and plus or minus...I picked plus.

But clearly there is more than one way to skin a cat.

I use an inside the neck sizing mandrel for autoloaders. I size the neck .003" under bullet diameter for AR platform rifles and have had great luck with these:
https://21stcenturyinnovation.com/buy-online/ols/products/caliber-specific-expander-mandrel

There are too many variations in neck wall thickness for me to be comfortable using bushing dies. Neck tension is only as good as the consistency of brass case wall thickness with the bushings. The mandrel dies that are similar in style to what I posted are a much better choice IMHO.

I too have the 21st Century Mandrel Die and mandrels (bought the set for the caliber...bit of overkill). Great product.

While the 21 Century mandrels do also come in .0005" increments, I still like having the pin gauges for measuring the results after mandrel neck expansion (don't ask me why...I think I had a reason at the time! haha).

It looks like (I think) that 21st Century has expanded their mandrel product offering a bit. All good.

Cheers

 

[Rocketmandb]

This....either an inside micrometer (hard to find for our small distances and expensive) or buy a few pin gauges. I have not found that I can get high accuracy/consistent I.D. measurements with a caliper but maybe that's just my lack of skills.

Have you found somewhere where you can buy a relatively small set? I've got a big set for smaller calibers, and would have to buy two more really big sets to cover my larger calibers - which I really don't want to do.

 

[Baron23]

Have you found somewhere where you can buy a relatively small set? I've got a big set for smaller calibers, and would have to buy two more really big sets to cover my larger calibers - which I really don't want to do.

You can order them individually from 21st Century. Just add the ones you need.

https://21stcenturyinnovation.com/buy-online/ols/search?keywords=mandrel&sortOption=descend_by_match

What caliber(s) is it you are looking for?

Am I missing something here?

 

[Rocketmandb]

You can order them individually from 21st Century. Just add the ones you need.

https://21stcenturyinnovation.com/buy-online/ols/search?keywords=mandrel&sortOption=descend_by_match

What caliber(s) is it you are looking for?

Am I missing something here?

I didn't realize they sold it - and I'm on their site quite a bit. Goes to show you how crappy their website is

EDIT: Just went there and didn't see pin gauges - that's what I'm looking for.

 

[Baron23]

I didn't realize they sold it - and I'm on their site quite a bit. Goes to show you how crappy their website is

While I have your attention...you may remember that I'm a q-tip painter with Neo Lube and you are a dipper.

Have you have data/statistics showing any difference in performance between the two techniques.

I sort of remember you saying you were going to try both and see how the SD's came out....but I might be hallucinating again!

 

[Rocketmandb]

While I have your attention...you may remember that I'm a q-tip painter with Neo Lube and you are a dipper.

Have you have data/statistics showing any difference in performance between the two techniques.

I sort of remember you saying you were going to try both and see how the SD's came out....but I might be hallucinating again!

I didn't see any difference in performance. For me, it was speed of doing it.