Question on pin gages vs. expander mandrels

[rady]

Never used pin gages before, so I'm curious about this product or others that may provide better results than expander mandrels?

https://portersprecisionproducts.com/expander-mandrel-die/

Trying to make a decision on the 21st Century incremented expander mandels or other products similar to the above, so your opinions would really help out. What would be the best way to size the gage pins with regard to +/- 0.0002error for a particular caliber like 6.5 CM (0.264)?

 

[OREGUN]

Um…those are expander mandrels…he just specifies that he makes them using pin gauges that he modifies by tapering/polishing…don’t over think this. The linked set or the 21st century set will serve you well to expand case necks to desired dimensions. If you want a set of pin gauges for measurement purposes, buy pin gauges.

 

[rady]

Um…those are expander mandrels…he just specifies that he makes them using pin gauges that he modifies by tapering/polishing…don’t over think this. The linked set or the 21st century set will serve you well to expand case necks to desired dimensions. If you want a set of pin gauges for measurement purposes, buy pin gauges.

Will the 21st mandrel set(s) work in the Sinclair gen II expander body?

 

[OREGUN]

It has a mandrel but it’s actually a collet die. It sizes the brass down squeezing it to the mandrel. It’s not intended to open up brass that’s already been sized down like so many of the mandrel expanders do that get discussed these days.

I would pair this Porter collet die with a body die.

I guess I would need some clarification from porter….I didn’t read the description this way. I assumed the collets were being used to hold the mandrel…

at any rate, not sure about the Sinclair expander body working with 21st century mandrel…but, they have excellent CS so an email should answer that question.

 

[spife7980]

I guess I would need some clarification from porter….I didn’t read the description this way. I assumed the collets were being used to hold the mandrel…

at any rate, not sure about the Sinclair expander body working with 21st century mandrel…but, they have excellent CS so an email should answer that question.

I deleted it, youre right. too early for me I guess. I was conflating the porter and the larry willis together into some dumb abomination of imagination.

 

[Steel head]

I deleted it, youre right. too early for me I guess. I was conflating the porter and the larry willis together into some dumb abomination of imagination.

 

[918v]

Pin gauges are shaped to gauge. Expander mandrels are shaped to expand. Use the correct tool for the job.

 

[Rocketmandb]

Pin gauges are shaped to gauge. Expander mandrels are shaped to expand. Use the correct tool for the job.

Pin gauges can also make for a really fun game of pick up sticks in certain situations.

 

[rady]

Pin gauges are shaped to gauge. Expander mandrels are shaped to expand. Use the correct tool for the job.

Ok..........So if I use the 21st to expand and pin gages to measure, do I go to the + or - side for the error in spec.'ing out the gages? Looking at McMaster Carr, they are pretty expensive (ZZ type). I could just use the cheaper tapered pins from the above vendor or is there a better/cheaper source?

 

[whatsupdoc]

Never used pin gages before, so I'm curious about this product or others that may provide better results than expander mandrels?

https://portersprecisionproducts.com/expander-mandrel-die/

Trying to make a decision on the 21st Century incremented expander mandels or other products similar to the above, so your opinions would really help out. What would be the best way to size the gage pins with regard to +/- 0.0002error for a particular caliber like 6.5 CM (0.264)?

Porters die uses a collet to hold a modified a gauge pin to expand your necks, his setup allows you to choose a neck
tension outside of what a standard expander mandrel or turning mandrel would provide.


As far as the gauge pin + or - , it really will not matter as you are not checking a machined hole. The resizing die the mandrel and the hardness of the brass will affect how much the brass springs back. I use the minus pins.

 

[OREGUN]

It would surprise me a little bit if you were capable of measuring or noticing a difference in .0002”. The reality is a couple mandrels sized in whole .001” is all you’ll need. Your sizing die will squish your neck down to whatever size its set up for And then you’ll use a mandrel to bring the neck back up to the dimension that gives you the neck tension you like. Maybe a half thou (.0005) will allow you to fine tune but it’s unlikely that you’ll notice if it’s a plus .0002” or minus .0002” mandrel. If you were gauging a machined hole and needed to decide if a slightly under size or slightly oversized hole was acceptable, the plus or minus engages would make a difference. For our purposes, it’s just slicing the pie to thin to matter.

Edited to include:
Sinclair’s expander mandrel for 6.5 is advertised at .263”and their turning mandrel is advertised at .262”. If it was me, I would buy one of each of those and probably one in the middle, at .2625”. I usually have really good results by just running the expander manual through brand new brass before seating and then sizing/expanding based on its use and the coordinating neck bushing. In the case of one of my 6 mm set ups, I have wanted a bit more tension than that so I’ve been experimenting with using the slightly smaller turning mandrel after resizing. It might just be a touch too small and I’ve been considering ordering a half size mandrel in the middle. In either case the whole process is as much based on feel as it is on hard measurements. Things like brass hardness and spring back make it nearly impossible, in my experience, to use math to come up with the exact size you want. The math may look great on paper but the seating feel or the tension is just not what you want. It’s a little bit of trial and error.

 

[powdahound76]

Will the 21st mandrel set(s) work in the Sinclair gen II expander body?

Yes, will work.

at least according to the website….
Or call them.
wonderful folks at 21st.

 

[powdahound76]

Also, why measure?

Seems shooting is the key and see what runs the best.

I see this in my work.
Spend time and $ running down data that serves little to no purpose.
What is measuring after expanding going to tell you that the targets dont?
Try different things. See what works best.
run that.

Not trying to be a jerk, just questions I have and I often sound like an ass according to my ex wife.

 

[rustyinbend]

Trying to make a decision on the 21st Century incremented expander mandels or other products similar to the above, so your opinions would really help out. What would be the best way to size the gage pins with regard to +/- 0.0002error for a particular caliber like 6.5 CM (0.264)?

I was struggling with pressure signs on 6.5-CM loads that had velocities that should never have had them. A guy I trust said to try a larger expander mandrel, and I told him I used the L.E. Wilson expander mandrel (one size ... "2630") and didn't think it was that. He convinced me to buy the 21st Century "Kit" with 9 sizes. Lo and behold ... the "2645" mandrel seated my bullets smoother, and totally solved my pressure problems. Made a believer out of me. I obviously recommend you buy the 21st Century die and expander mandrel kit. The really good 6.5-CM kit results prompted me to order the 300-caliber kit a few days ago.

 

[Rocketmandb]

What is measuring after expanding going to tell you that the targets dont?

It's going to tell you where your issue is and where you can get better. An arbor press with a force gauge is somewhat of a proxy for this.

 

[OREGUN]

What is measuring after expanding going to tell you that the targets dont?

About the only reason I measure is so that I have a reference point on deciding which neck bushing and which mandrel to use in the future (to keep things consistent) and to know where my brass is in relation to my chamber neck dimensions. Whether or not I think I have enough tension to hold a magazine fed bullet versus a single fed bullet is a consideration but one that can’t really be answered by doing the math…and is subject to the discussion about plasticity of brass… is there actually any such thing as neck tension over a certain amount because of the way brass expands?

 

[Dthomas3523]

Also, why measure?

Seems shooting is the key and see what runs the best.

I see this in my work.
Spend time and $ running down data that serves little to no purpose.
What is measuring after expanding going to tell you that the targets dont?
Try different things. See what works best.
run that.

Not trying to be a jerk, just questions I have and I often sound like an ass according to my ex wife.

Because once you know what works on paper, measuring tells you (for the most part) when something is either A) wrong with your process or B) something is up with that particular piece of brass and likely won’t be as consistent.

For the OP, buy the 21st century set of whatever you’re loading (6mm, 6.5, .308, etc).

Then get the pin gauges of the inside diameter/s you want. For example, I have .241 .2415 and .242.

Decide which inside diameter you want with your current batch of ammo, and experiment with mandrels until you get the desired fit on the pin gauge. That mandrel *should* work for the rest of that batch. Check every so often with pin gauge (or every one if you want to go ape shit) and make sure you’re still getting the desired fit.


Keep in mind, as brass is used (despite annealing at times) you may need a slightly different mandrel next time. For example, I’ve had to change from .242 to a .2425 after X amount of firings to retain the fitment I want on the chosen pin gauge.

 

[Dthomas3523]

Large issue I see with people loading ammo is they really don’t know what the ID of their brass actually is.

They either do math that doesn’t account for spring back or they account for too little/too much spring back. Or, they measure with calipers which won’t give you a good reading for something like this.

Pin gauges solve this. No math or anything else. If you want .241 ID for .002 “neck tension” then you try the mandrels around .241, .2415, .242 and see which one gives you the desired fit on the .241 pin gauge.

Test at range with brass that fits .241, .2415, .242 pin gauges and decide what to run. Now that becomes another comparator QC check. Use it to pick the proper mandrel next batch and to QC check.

Things like this are the culprits of “my load fell apart.” Small things that either add up or have a large enough factor to change the way the ammo behaves.

Real “load development” isn’t one and done. Though it’s not hard if done properly, it’s something you keep and eye on for the life of the barrel and brass. Pin gauges and other QC checks help you keep your brass in optimal condition without having to guess.

 

[OREGUN]

Ok..........So if I use the 21st to expand and pin gages to measure, do I go to the + or - side for the error in spec.'ing out the gages? Looking at McMaster Carr, they are pretty expensive (ZZ type). I could just use the cheaper tapered pins from the above vendor or is there a better/cheaper source?

Dthomas3523 gives good advice. I don’t have pin gauges and thus don’t try to measure the inside diameter after I’ve expanded. I don’t think this is necessarily a required step. I use seating “feel” or the arbor press pressure indicator to tell me if things are consistent and would lose my mind pin gauging my brass. Of course that means I occasionally start out in the seating process and realize I should maybe have used a different mandrel. As an aside, I also tend to think that when people “have their load fall apart“, it’s because they shot like shit that day and don’t want to admit it.

The advantage I see with the Porter gear is that if you knew exactly what you wanted you could buy individual mandrels instead of buying a whole set. Considering you don’t know exactly what you want the 21st-century set is probably a better deal (I didn’t look at the prices so maybe it’s not). And to specifically answer your question, if Porter is using modified pin gauges to make his expander mandrels, then yes, you could buy his mandrels and use them as pin gauges for your purposes. Above the taper at the end (added to make them start easier) they should be a constant and specific diameter.

 

[spife7980]

When I was looking into porter a few years ago one of the big advantages was you could just get your pin gauges from amazon for a couple bucks only each and just grind the end taper yourself. It wasnt dependent on mandrels coming from only him.

 

[powdahound76]

Good answers.

makes sense.

my stuff shoots. Guess I have been lucky

 

[OREGUN]

Guess I have been lucky

I think it is equally likely that, like you said, some of the stuff that we spend time and money measuring and stressing over is not nearly as critical as we like to think it is.

 

[PatMiles]

When I was looking into porter a few years ago one of the big advantages was you could just get your pin gauges from amazon for a couple bucks only each and just grind the end taper yourself. It wasnt dependent on mandrels coming from only him.

The beauty of the Porter Precision unit is the fact that the collet system accepts a range of pin gauges so fitting the perfect diameter pin gauge is a just matter of installing another pin gauge. As Spife tells above, they are available on Amazon for around $5.00 each. The collets that fit the Porter die (ER-32 I believe) are standard size and available on Amazon and many machine tool websites so you can easily and inexpensively buy complete setups for different calibers.
To put a taper on the pin gauges just chuck one up in a cordless drill and spin it up against a belt sander using finer and finer grits of sanding belts. Polish with 600 grit and then finer sheets of sandpaper then crocus cloth. If you have access to a lathe or mill you are golden.

 

[PatMiles]

I think it is equally likely that, like you said, some of the stuff that we spend time and money measuring and stressing over is not nearly as critical as we like to think it is.

Individually that is true, but when you start putting several "not as critical" steps together they do amount to something.

 

[rady]

Great information here fellows and it really helps. I was looking at a video that F Class John did on yt involving the above Porter system. Good presentation for those of you that may not be familiar with all of this.

I was struggling with pressure signs on 6.5-CM loads that had velocities that should never have had them. A guy I trust said to try a larger expander mandrel, and I told him I used the L.E. Wilson expander mandrel (one size ... "2630") and didn't think it was that. He convinced me to buy the 21st Century "Kit" with 9 sizes. Lo and behold ... the "2645" mandrel seated my bullets smoother, and totally solved my pressure problems. Made a believer out of me. I obviously recommend you buy the 21st Century die and expander mandrel kit. The really good 6.5-CM kit results prompted me to order the 300-caliber kit a few days ago.

Was this the over pressure problem that you were speaking of with the Tikka gun a few weeks ago? If it is, I'm glad that 21st provided the solution.
The problem I'm having is getting consistent neck tension, so I will be getting a set of the 21st mandrels. My guess is that I am overly reliant on the dial calipers for determining neck tension.

Dthomas3523 gives good advice. I don’t have pin gauges and thus don’t try to measure the inside diameter after I’ve expanded. I don’t think this is necessarily a required step. I use seating “feel” or the arbor press pressure indicator to tell me if things are consistent and would lose my mind pin gauging my brass. Of course that means I occasionally start out in the seating process and realize I should maybe have used a different mandrel. As an aside, I also tend to think that when people “have their load fall apart“, it’s because they shot like shit that day and don’t want to admit it.

The advantage I see with the Porter gear is that if you knew exactly what you wanted you could buy individual mandrels instead of buying a whole set. Considering you don’t know exactly what you want the 21st-century set is probably a better deal (I didn’t look at the prices so maybe it’s not). And to specifically answer your question, if Porter is using modified pin gauges to make his expander mandrels, then yes, you could buy his mandrels and use them as pin gauges for your purposes. Above the taper at the end (added to make them start easier) they should be a constant and specific diameter.

Exactly. The one end is not tapered, so you have a straight out pin gage to measure the neck opening. I plan on starting with the 21st mandrels, then look at the Porter mandrels as a pin gage. The video I reference above does a good job of showing how the whole system is constructed.

 

[Baron23]

the "2645" mandrel seated my bullets smoother, and totally solved my pressure problems.

Pardon my naive question....but .0005 wider than bullet diameter?

Spring back maybe....I mean, you do obviously have some neck tension.

Again, pardon my ignorance if this is a stupid question.

 

[OREGUN]

Pardon my naive question....but .0005 wider than bullet diameter?

Spring back maybe....I mean, you do obviously have some neck tension.

Again, pardon my ignorance if this is a stupid question.

Spring back.

 

[918v]

It would surprise me a little bit if you were capable of measuring or noticing a difference in .0002”. The reality is a couple mandrels sized in whole .001” is all you’ll need. Your sizing die will squish your neck down to whatever size its set up for And then you’ll use a mandrel to bring the neck back up to the dimension that gives you the neck tension you like. Maybe a half thou (.0005) will allow you to fine tune but it’s unlikely that you’ll notice if it’s a plus .0002” or minus .0002” mandrel. If you were gauging a machined hole and needed to decide if a slightly under size or slightly oversized hole was acceptable, the plus or minus engages would make a difference. For our purposes, it’s just slicing the pie to thin to matter.

Edited to include:
Sinclair’s expander mandrel for 6.5 is advertised at .263”and their turning mandrel is advertised at .262”. If it was me, I would buy one of each of those and probably one in the middle, at .2625”. I usually have really good results by just running the expander manual through brand new brass before seating and then sizing/expanding based on its use and the coordinating neck bushing. In the case of one of my 6 mm set ups, I have wanted a bit more tension than that so I’ve been experimenting with using the slightly smaller turning mandrel after resizing. It might just be a touch too small and I’ve been considering ordering a half size mandrel in the middle. In either case the whole process is as much based on feel as it is on hard measurements. Things like brass hardness and spring back make it nearly impossible, in my experience, to use math to come up with the exact size you want. The math may look great on paper but the seating feel or the tension is just not what you want. It’s a little bit of trial and error.

Whatever diameter mandrel you choose depends on your sizing die. The more the neck is sized the bigger the mandrel needs to be to overcome springback.

I was hoping the Porter setup had correctly shaped pins. That bevel on one end is half ass. A correctly shaped expander has a gradual taper.

I use PMA Tool carbide mandrels and adjust seating pressure by using different diameter mandrels for my Lee collet neck die.

 

[Rumlover]

Yes, will work.

at least according to the website….
Or call them.
wonderful folks at 21st.

They do work with the Sinclair die, I'm using them. The 21st Century mandrels are slightly tighter in the Sinclair die than the Sinclair mandrel, touch of lube and slides right in--'bout like prom night.

 

[NamibHunter]

After reading this i got the mandrel die from Porter Precision Products (P3, a company based in Lake Jackson Tx, close to Houston). Bought a set of low cost pin gauges from Amazon in 0.5 thou increments (0.0005”), and then shaped them (gradual taper) using a Dremel. The setup works really well, and very happy with it.

Can now accurate control neck ID, and compensate for springback differences as the brass ages, and get back to the same seating force as before when i switch from an old batch of Lapua brass (retired at 25 firings) to new Lapua brass (both from the same original box). Very easy to get speed and interference fit the same as before, keeping group size almost the same. [Had to adjust the powder charge by 0.1 gn, as the new batch is slightly thicker. The originally batch was weight sorted into two groups of 2 grains each.]

As said before, every mandrel/pin serves as a pin gauge for measuring via the and as an expander mandrel when clamped in the die. You don’t need to buy the super accurate pin gauges ($20), and the cheaper $5 versions work fine, just double check them with a micrometer to 0.1 thou accuracy, and write that on the pin with a permanent marker.

I am sure the 21’st Century set would work just as well, but if you run multiple calibers, the P3 mandrel die combined with low cost Amazon gauge pins is cheaper, and more flexible.

 

[sirhrmechanic]

Pin gauges can also make for a really fun game of pick up sticks in certain situations.

So can expander balls…. %#]*+!!!!

BTDT.

Sirhr

 

[NamibHunter]

I figured out that the AMP machine (using the Aztec code) makes the neck soft enough that you cannot run anything more than 1.5-2 thou of interference fit without the bullet resizing the neck. Tested on 6.5 CM Lapua brass - neck turned to 12 thou.

Springback is about 0.5-0.7 thou with 12x fired Lapua brass, annealed every time, and worked as little as possible. Max seating force is 41 - 45 lbs with a 0.2620” mandrel (6.5 CM so 264 bullet diameter), but if you pull the bullet, the neck OD has gone up compared to prior to bullet seating. The bullet is clearly resizing the neck!

As an experiment, i tried different mandrels/pin gauges:

0.2640” mandrel: Mandrel is actually -0.2 thou below bullet diameter (0.2638”) according to the Hornady micrometer, which has been calibrated against an accurate gauge block. So “neck tension” is mostly due to brass springback in this case (about 0.7 thou). It gave fairly light but consistent seating force, and measured with the K&M arbor press, seating force varied between 12 and 16 lbs. That is consistent enough for 800 yard ammo. [Btw: At 2-4 lbs you can rotate the bullet by hand, which is a bad thing, not magazine safe, impractical.]

0.2635 Mandrel: At a nominal 0.5 thou below bullet diameter (actual measurement is 0.2634”) it gave seating force between 18 and 21 lbs. The actual interference fit is 0.7+0.6=1.3 thou due to 0.7 thou of springback. This ammo works fine in mag fed rifles. Accurate too, 0.4” groups.

0.2630: Mandrel is on order.

0.2625 Mandrel: Nominally 1.5 thou under bullet size gave 32 to 41 lbs during seating, which is high. Neck was resized by the Berger Hybrid bullet. Pin gauge that fits is the 0.2635 but it is slightly loose, i expect a 0.2630 gauge would have been a tight fit. [Waiting for this pin to arrive.] Pressure ring shows a bright “wear” mark (probably just some minor damage).

2.0 thou seems to be slightly beyond the highest amount of achievable neck tension / interference fit for 12x fired Lapua brass that is worked as little as possible and annealed every time. Seating force peaks at about 40-45 lbs, which is high but workable for hunting ammo. Too high for target ammo IMO. [Btw: At 60-80 lbs the seating stem will start to damage the bullet. Impractical.]

A mandrel 2.5 to 3.0 thou below bullet diameter would (maybe) work ok on old brass that has not been annealed in a long time. Have not tried that yet.

Porter Precision mandrel works well and i would recommend it. Fast friendly service too.

Probably no point in ordering pins below 2.5 or 3 thou smaller than your bullets.

 

[OREGUN]

That’s the best write up of that I’ve seen. Thanks!

 

[NamibHunter]

An interesting observation was that “almost identical” brass (same weight, same prep) has somewhat different springback, which changes the seating force (which is proportional to actual interference for, commonly referred to as “neck tension”). Even if you neck turn all of them and reduce neck thickness (all the way around the entire case) by 1.5 thou (so not a skim turn), and then mandrel expand them, you will find that seating force will still vary some amount, around 20%.

1) One source of variability is that neck turning using hand tools (as opposed to a lathe) still leaves about 0.15 to 0.2 thou of variability according to the (expensive made-in-Japan) micrometer….

2) We all know that the cases used for pressure testing have been work hardened and stretched quite a bit more than the ones fired at lower charges.

3) Also different cases might have a different number of firings on them - even if you try to avoid that!

4) Who knows, brass compositions night also be slightly different…. I have seen cases expand different amounts at the web area (near case head) when firing 3 rounds that are slightly above max.

5) Did the cases all grip the chamber in the same way during firing? Annealed necks have a higher coefficient of friction that polished necks. It will probably move back less towards the bolt before gripping the chamber. That will cause a different amount of stretch.

6) Necks can thin at a different rate: If you trim all your cases, and measure case length when you come back from a range session, there is a remarkable difference there, around 5-7 thou for 6.5 CM. Other calibers with different shoulder angles do better. Which means some necks are getting thinner at a faster rate than others.

7) Some cases might just be softer than others - metallurgical differences, who knows.

My point is that getting seating force dead constant is a good goal, but not really 100% achievable. But you can sort or cull the loaded rounds based on seating force, and that does help a bit.

 

[NamibHunter]

Some pictures:

The 0.2610” and 0.2615” mandrels top left will probably never get used….

 

[NamibHunter]

Die appears to be nitrided, so very scratch resistant.

If you don’t like the constant bevel on the end of their pins, just contour it the way you like it.

 

[NamibHunter]

Concentricity improved compared to the Redding Type S die, from 1.0-3.5 thou of bullet runout, to 0.5 to 2.0 (average is now around 1.3 thou). True for all well made mandrel dies.

Not that small concentricity errors matter that much…. In my experience, anything below 5 thou works well enough out to 600 yards. For 1000 plus or ELR ammo, it probably does help to get it below 1.5 thou. I know BR folks aim for 1.0 thou, so they cull out the bad ones, and use those for practice.

 

[NamibHunter]

Spoke too soon about never using the smaller pins below 0.2625”: They are really useful for measuring the progression of our beloved donuts in the neck-shoulder area: In brass from once fired Hornady brown box ammo, AMP annealed, not neck turned (1-1.2 thou neck thickness variation), then sized down about 2 thou using a custom Forster FL die with a honed neck ID of 0.2860” (sizing button removed). Then seated a bullet which resized the neck ID to 0.2635 or just a hair below that.

The donut blocks a 0.2620 pin - but it fits with almost no wiggle room in the neck. The 0.2615 pin just barely goes through the donut under slight pressure, and it has some wiggle room in the neck.

So the donut ID is close to 2 thou (likely between 1.8 and 2.2) after just one firing. Really, so soon?!

If you then run the 0.2635 mandrel through the neck using the P3 mandrel die in the press, it does not resize the neck, but it does resize the donut. Now the 0.2620 pin will easily go through all the way, but the 0.2625 pin will get stuck at the donut. So the donut is 0.5 thou enlarged, and is still close to 1.5 thou smaller than neck ID.

If i put the expander ball assembly back in the Forster FL die, which has a 0.2627” diameter, it does a better job with the donut, and the same 0.2620 pin will fit fairly tightly in the case neck but is quite tight in the donut area, but it does go through with moderate finger pressure. Donut and neck IDs are closer to 0.2-0.3 thou. Maybe just a case of luck.

Or maybe a well made FL die with the correctly sized neck for your chamber, and a correctly sized button does have some advantages?

 

[NamibHunter]

I hate to admit it, but my OCD has kicked in. Now i want gauge pins that are 0.2 thou apart! Oh boy.

Will have to buy them over sized and polish them down on my own. New rabbit hole!

Edit/Add: Recently realized that there is a way to get low cost pins that are approximately 0.25 thou apart: “Minus” pins are (usually) between 0.1 to 0.3 thou below size, while “Plus” pins are usually 0.1-0.3 thou above the stated size. So with some luck, you could get a 0.2637 pin and a 0.2642 pin. Not exactly 0.25 thou apart, but close. You will need a good micrometer to confirm exact OD.

It could be one way to fine tune interference fit. [In my testing, 0.5 thou proved to make a big difference to seating force.]

 

[NamibHunter]

F-class John did a video on this die:

 

[NamibHunter]

Found another good use for the Porter Precision mandrel die: Dealing with donuts.

Lapua 6.5 Creedmoor SRP brass developed a chunky donut at the neck shoulder junction after about 10 or so reloads, all FL sized with a Whidden non-bushing die. Wanted to cut the donuts out with a Wilson inside neck reamer. The cutter was probably designed for new brass, and my Savage 12 leaves the fired brass in a state where the cutter does not touch the neck. Measured the cutter diameter, added 0.5 thou for brass springback and ordered an oversize 0.2675”+ gauge pin ($5). Then FL size the brass, clamp the gauge pin in the Porter Precision die, push the mandrel/gauge pin through the neck, and it ended up at the perfect diameter for cutting out most of the donut. Rest of the inside neck was mostly left intact.

 

[NamibHunter]

Would also be useful if you are trying to neck up say 6.5 mm brass to 7 mm. Can buy cheap pins, bevel them yourself, and neck up and anneal in smaller increments.