Case sizing with mandrel - seating issues

[_Thor_]

I'm seeing something strange with my first batch of prepped cases after their first firing of some virgin 6GT alpha brass. My process was:

• Deprime with Lee depriming die
• No anneal, no trim (don't have the equipment)
• Lube and size with a Forster FL sizing die (no depriming stem or expander ball, just the die body)
• Mandrel with 21c .241 expander mandrel (relying on leftover wet RCBS lube)
• No chamfer (I've read some say they don't bother)
• Wet tumble 1hr with dawn/water, rinse thoroughly
• Drain and tumble overnight with walnut + some car polish
• Collect cases, remark, prime, charge
• Seat with Forster micrometer die

The weirdness came in when I got all the way to the end and tried seating my first 5 bullets (6mm 109 ELDMs). I had ridiculous seating force which of course marred a huge ring into each bullet. I knew this was wrong but was feeling hard-headed and finished the row.

I messed around with re-mandreling my cleaned brass and adding dry lube to the bullets themselves and found some partial success with some smoother seating force, but not 100%, and my BTO measurements would vary around 10-20 thousandths unless I chased my target depth by adjusting my micrometer die.

I noticed that the force of seating was shaving the bullets and producing small rings of metal, so I tried a quick chamfer and deburr. Suddenly without mandreling again, it seats much better. However, during this whole process I measure my brass neck ID with micrometer and find them measuring around .232-.234 ... smaller than I'd expect after expanding with a mandrel. Did the tumble close my necks back up?!? I wondered if my micrometer measurements were wrong because of the square jaw/circular surface problem so I got some pin gauges. Sure enough, I'm seeing these measurements, which I assume are trustworthy from the pin gauges:

• Unprocessed, once-fired brass: .241 - .243
• Sized/mandreled/tumbled brass: .230
• Re-mandrel once: .239 - .240
• Re-mandrel - 10+ strokes: .240

Any explanation for the processed brass "shrinking" in ID? I would expect to mandrel once before tumbling and then be all seat. Is the chamfer really responsible for my seating going more smoothly, or is it all an artifact of my oddly-small necks? And lastly - I would assume all of those seated without re-mandreling are under much more neck tension - even the "smooth" ones that got chamfered, correct? I would assume seating those results in something like .013 of neck tension? Would that render these essentially useless for any target shooting?

 

[R_A_W]

You're peening the necks by tumbling overnight. Overloading your tumbler with too many cases makes this worse. I've seen -0.004" from 2 hours of overloaded tumbling. Add in the fact that you haven't chamfered the inside of the necks... yeah, you're going to have a ton of seating force. I bet you are shaving jackets.

e: I have a friend that tumbles overnight, but he sizes & mandrels 2x after that.

If you want to tumble for a long period to get your brass really clean, I would do that before you size/mandrel, then a shorter tumble just to remove lube

 

[Kaldor]

You're peening the necks by tumbling overnight. Overloading your tumbler with too many cases makes this worse. I've seen -0.004" from 2 hours of overloaded tumbling. Add in the fact that you haven't chamfered the inside of the necks... yeah, you're going to have a ton of seating force. I bet you are shaving jackets.

e: I have a friend that tumbles overnight, but he sizes & mandrels 2x after that.

If you want to tumble for a long period to get your brass really clean, I would do that before you size/mandrel, then a shorter tumble just to remove lube

This.
You're peening the necks. Size, tumble, then mandrel to avoid that. Use a bit of dry lube on the case neck if you think its warranted before mandrel. Also, start trimming before you get yourself into a high pressure situation on stretched brass. A trimmer is alot less expensive than a rifle or injuring yourself.

 

[rustyinbend]

You lost me at "... no anneal ...".

 

[straightshooter1]

I'm seeing something strange with my first batch of prepped cases after their first firing of some virgin 6GT alpha brass. My process was:

• Deprime with Lee depriming die
• No anneal, no trim (don't have the equipment)
• Lube and size with a Forster FL sizing die (no depriming stem or expander ball, just the die body)
• Mandrel with 21c .241 expander mandrel (relying on leftover wet RCBS lube)
• No chamfer (I've read some say they don't bother)
• Wet tumble 1hr with dawn/water, rinse thoroughly
• Drain and tumble overnight with walnut + some car polish
• Collect cases, remark, prime, charge
• Seat with Forster micrometer die

The weirdness came in when I got all the way to the end and tried seating my first 5 bullets (6mm 109 ELDMs). I had ridiculous seating force which of course marred a huge ring into each bullet. I knew this was wrong but was feeling hard-headed and finished the row.

I messed around with re-mandreling my cleaned brass and adding dry lube to the bullets themselves and found some partial success with some smoother seating force, but not 100%, and my BTO measurements would vary around 10-20 thousandths unless I chased my target depth by adjusting my micrometer die.

I noticed that the force of seating was shaving the bullets and producing small rings of metal, so I tried a quick chamfer and deburr. Suddenly without mandreling again, it seats much better. However, during this whole process I measure my brass neck ID with micrometer and find them measuring around .232-.234 ... smaller than I'd expect after expanding with a mandrel. Did the tumble close my necks back up?!? I wondered if my micrometer measurements were wrong because of the square jaw/circular surface problem so I got some pin gauges. Sure enough, I'm seeing these measurements, which I assume are trustworthy from the pin gauges:

• Unprocessed, once-fired brass: .241 - .243
• Sized/mandreled/tumbled brass: .230
• Re-mandrel once: .239 - .240
• Re-mandrel - 10+ strokes: .240

Any explanation for the processed brass "shrinking" in ID? I would expect to mandrel once before tumbling and then be all seat. Is the chamfer really responsible for my seating going more smoothly, or is it all an artifact of my oddly-small necks? And lastly - I would assume all of those seated without re-mandreling are under much more neck tension - even the "smooth" ones that got chamfered, correct? I would assume seating those results in something like .013 of neck tension? Would that render these essentially useless for any target shooting?

I take it you're wet tumbling without SS pins?

Whether wet tumbling with or without SSP, the cases beat on each other where the case mouths are very susceptible to peening where the edge of the mouth is bent inwards and can result with the ID reduced when the there's been no chamfering. Even with chamfered necks, there a problem with peening resulting in seating issues.

An hour of wet tumbling is a long time and the longer the time the more the peening. You can get just as good results with a shorter time, like just 1/2 hr. . . especially if you use hot water. After wet tumbling, you should always chamfer the neck mouths to removed any of the peening. Typically, dry tumbling doesn't have this problem, unless of course, you do it for excessive time. And I'd say, doing it overnight is way way longer than needed.

 

[Baron23]

case mouths are very susceptible to peeing

At 73, I'm very susceptible to peeing too! hahaha

 

[JerkyFreak]

The person that told you not to bother chamfering, take him off your list of people-to-listen-to. That is possibly the worst advice he could have given you.

Unless he wanted you to load crappy ammo. In which case, take him off your friends list.

 

[_Thor_]

This.
You're peening the necks. Size, tumble, then mandrel to avoid that. Use a bit of dry lube on the case neck if you think its warranted before mandrel. Also, start trimming before you get yourself into a high pressure situation on stretched brass. A trimmer is alot less expensive than a rifle or injuring yourself.

This is interesting, because I've definitely seen some people claim to size, mandrel and then tumble. Maybe they just do it for a shorter time than I did. It definitely seems like the most logical step to change the order of operations as you suggested. I do find it interesting that just-mandreled brass settles around .239-.240 for a .241. I guess that's "spring back"? I went with a .241 mandrel based on others' suggestions and hoping for 2-thou-or-so of neck tension, but I guess a .242 would have been a better choice.

A trimmer is probably in my future. At least those are somewhat within my budget. I'm curious if you chamfer even when not trimming though?

You lost me at "... no anneal ...".

I wish I could drop $300-$700 on an annealer but it's really not feasible for me. I saw a post on here somewhere where someone said it's better not to bother annealing vs doing a shoddy inconsistent job by hand. I guess I'm shortening the life of my brass to maybe 4-5 firings, then? But with a set of 300 cases, that might even get me through most or all of this barrel's life. Granted, annealing saves money on a long enough timeline.

I take it you're wet tumbling without SS pins?

Whether wet tumbling with or without SSP, the cases beat on each other where the case mouths are very susceptible to peeing where the edge of the mouth is bent inwards and can result with the ID reduced when the there's been no chamfering. Even with chamfered necks, there a problem with peening resulting in seating issues.

An hour of wet tumbling is a long time and the longer the time the more the peening. You can get just as good results with a shorter time, like just 1/2 hr. . . especially if you use hot water. After wet tumbling, you should always chamfer the neck mouths to removed any of the peening. Typically, dry tumbling doesn't have this problem, unless of course, you do it for excessive time. And I'd say, doing it overnight is way way longer than needed.

Correct, no pins, just the hour with water/dawn and brass. Maybe the shorter wet cycle was the more likely culprit over the overnight with walnut then. I don't think the drum was highly loaded - maybe 70 pieces total. I think following Kaldor's suggestion and yours should be a huge help:

• Lube/size
• 30 minute wet tumble
• Mandrel with dry lube
• Dry tumble
• Chamfer (after mandrel, I assume, not before?)
• etc

 

[CK1.0]

No outside deburr = fine (I only deburr the outside of the case mouths if it’s new brass or after I’ve freshly trimmed it).

No inside chamfer = no bueno. Bullets are expensive, skipping the inside mouth chamfer and scratching them is dumb.

Also, wet-tumbling is for blaster ammo only, precision cases needed to be treated more gently and only get dry-tumbled in my casa.

 

[MCHOG]

Do you have a compressed load? You might just be fighting a full case.

 

[Kaldor]

This is interesting, because I've definitely seen some people claim to size, mandrel and then tumble. Maybe they just do it for a shorter time than I did. It definitely seems like the most logical step to change the order of operations as you suggested. I do find it interesting that just-mandreled brass settles around .239-.240 for a .241. I guess that's "spring back"? I went with a .241 mandrel based on others' suggestions and hoping for 2-thou-or-so of neck tension, but I guess a .242 would have been a better choice.

A trimmer is probably in my future. At least those are somewhat within my budget. I'm curious if you chamfer even when not trimming though

My process is simple and I do this every firing on all my bolt gun brass:
Decap
Anneal with AGS annealer
Size with FL die, no expander
Wet tumble for 1 hour, I do use pins, but it's fine without
Air dry overnight with fan
Sinclair TiN or carbide mandrel, they both work
Trim with Giraud with flat cutter
Chamfer/deburr, brush necks with VLD style tool and nylon brass on Lyman case prep center
Primer, powder, bullet, shoot, rinse, repeat...

Seems like a lot, but when you batch it out a few hundred pieces at a time, it goes fast. Yes, you are probably seeing some spring back. Is it a big deal? Not if it's consistent. You do need to trim like ASAP. Buying even an inexpensive gas annealer like an EP 2.0 will extend the lifespan of your brass and make neck tension more consistent. I mandrel post tumble because some peening is inevitable. Your your wet tumble is enough for bolt gun brass that stays clean so skip the dry tumble, it's just an extra step that's causing more harm than good

 

[straightshooter1]

At 73, I'm very susceptible to peeing too! hahaha

Just wait till you're my age, 78, and see what happens. It's an exponential curve.

 

[straightshooter1]

This is interesting, because I've definitely seen some people claim to size, mandrel and then tumble. Maybe they just do it for a shorter time than I did. It definitely seems like the most logical step to change the order of operations as you suggested. I do find it interesting that just-mandreled brass settles around .239-.240 for a .241. I guess that's "spring back"? I went with a .241 mandrel based on others' suggestions and hoping for 2-thou-or-so of neck tension, but I guess a .242 would have been a better choice.

You always get springback, unless your brass is dead soft, and that's something no one wants. How much springback you get will depend on the hardness of each piece of brass (the more you fire and size the cases without annealing, the harder the brass becomes).

A trimmer is probably in my future. At least those are somewhat within my budget. I'm curious if you chamfer even when not trimming though?

I trim and chamfer after every sizing session. Always chamfering assures me that any little bit of peening I might get is taken care of so that bullet seating is more consistent.

I wish I could drop $300-$700 on an annealer but it's really not feasible for me. I saw a post on here somewhere where someone said it's better not to bother annealing vs doing a shoddy inconsistent job by hand. I guess I'm shortening the life of my brass to maybe 4-5 firings, then? But with a set of 300 cases, that might even get me through most or all of this barrel's life. Granted, annealing saves money on a long enough timeline.

You can get a nice annealing machine for under $300, well . . . at $300 after tax. If you've got some mechanical talent, you could probably build something for much less. Annealing not only extends case life, it really helps a lot with consistent sizing results (like way less springback and more consistent bullet seating).

Doing a decent annealing job is NOT hard to do well enough. You just need a little understanding of what it takes in terms of the amount of heat and the time at that heat to get the job done. It's NOT rocket science. But this is a lot of misinformation floating around for beginners to be confused . . . just like that comment about "better not to bother annealing vs doing a shoddy inconsistent job by hand."

Correct, no pins, just the hour with water/dawn and brass. Maybe the shorter wet cycle was the more likely culprit over the overnight with walnut then.

Wet tumbling is very well known as being the culprit. Dry tumbling can do it too, depending on how it's loaded and the design the the tumbler. Like my cheap Frankford Arsenal dry tumbler has a threaded steel rod up the middle to tighten the lid on to it. That steel rod tended to produce some peening, so I put a thick plastic liner over it keep that from happening.

I don't think the drum was highly loaded - maybe 70 pieces total. I think following Kaldor's suggestion and yours should be a huge help:

• Lube/size
• 30 minute wet tumble
• Mandrel with dry lube
• Dry tumble
• Chamfer (after mandrel, I assume, not before?)
• etc

I'd suggest changing that order a little bit that should actually give you better results IMHO:

• 30 minute wet tumble (HOT water)
• Lube/size
• Dry tumble
• Chamfer (before mandrel, it helps the mandrel go in easier like it does for seating bullets)
• Mandrel with dry lube

I highly recommend you get a trimmer, even a cheap one as every time you size the brass, it'll grow in length . . especially when using no custom sizing dies.

PS: I do a 3-way trim at the very last of my processing.

 

[_Thor_]

You always get springback, unless your brass is dead soft, and that's something no one wants. How much springback you get will depend on the hardness of each piece of brass (the more you fire and size the cases without annealing, the harder the brass becomes).


I trim and chamfer after every sizing session. Always chamfering assures me that any little bit of peening I might get is taken care of so that bullet seating is more consistent.


You can get a nice annealing machine for under $300, well . . . at $300 after tax. If you've got some mechanical talent, you could probably build something for much less. Annealing not only extends case life, it really helps a lot with consistent sizing results (like way less springback and more consistent bullet seating).

Doing a decent annealing job is NOT hard to do well enough. You just need a little understanding of what it takes in terms of the amount of heat and the time at that heat to get the job done. It's NOT rocket science. But this is a lot of misinformation floating around for beginners to be confused . . . just like that comment about "better not to bother annealing vs doing a shoddy inconsistent job by hand."


Wet tumbling is very well known as being the culprit. Dry tumbling can do it too, depending on how it's loaded and the design the the tumbler. Like my cheap Frankford Arsenal dry tumbler has a threaded steel rod up the middle to tighten the lid on to it. That steel rod tended to produce some peening, so I put a thick plastic liner over it keep that from happening.

I'd suggest changing that order a little bit that should actually give you better results IMHO:

• 30 minute wet tumble (HOT water)
• Lube/size
• Dry tumble
• Chamfer (before mandrel, it helps the mandrel go in easier like it does for seating bullets)
• Mandrel with dry lube

I highly recommend you get a trimmer, even a cheap one as every time you size the brass, it'll grow in length . . especially when using no custom sizing dies.

PS: I do a 3-way trim at the very last of my processing.

Thanks, this is very helpful. The purpose of the wet tumble for me is partly to get rid of the lube, and partly to hopefully wash some of the lead away some I'm not spraying lead residue all over my space during the dry tumble. I would guess a dry tumble is just as good at removing the wet lube from sizing, maybe reducing the life of the dry media a little? And when you say you 3-way trim at the end - do you chamfer, then mandrel, then trim and chamfer/deburr again?

On that note - any recommendations for a trimmer? I've had the Lyman Universal Case Trimmer Kit with 9 Pilots on my "to buy" list for a long time, but I wonder if there are any better-liked options out there on the lower-end of the price range.

That's good information on the annealing too - I didn't realize it was so critical. What is the exactly-$300 option you were thinking of? It's possible I could attempt to cobble a DIY setup together, though sometimes that ends up being more expensive than buying the right thing in the first place.

 

[padom]

ALWAYS inside chamfer. ALWAYS

Skip the wet tumbling for your precision ammo. It hurts you more than it helps you. These days, I ONLY wet tumble range pickup pistol or 5.56 brass because they are filthy and corroded. This strips good carbon from the neck and makes the inside of the necks TOO clean. This causes varying seating pressure issues and galling, locking... This all hurts accuracy, SD's and seating pressure. Just not good.

Dry tumble your brass, throw a dryer sheet or two in the dry tumbler and put the lid on it, thats why they come with lids...

With Alpha 6GT 1x brass your issue is not lack of annealing or trimming.


Also, did you take proper measurements to determine your mandrel? Or just got what you read. Take a piece of fired brass, measure the neck, write that number down... Now size the case in your Forster FL Sizing die and measure the neck and write that number down... Now run that case in your mandrel and measure the neck once last time and write that number down... Now seat a bullet in this case and measure the neck one last time and write that number down.

Now take your once fired brass neck measurement and subtract the Forster FL sized neck measurement. This tells you/us how much you are squeezing the neck down from fired.

Now take the final number from above and subtract the number you got when you measured the neck after mandrel.. This tells us how much you are opening the neck back up after sizing with the Forster FL sizing die.

Now take final number from the above question and subtract the number you got when measuring a loaded case neck. This number tells us how much neck tension you have...



This will tell you how much your squeezing your neck down from fired with the Forster, how much your opening it back up with the mandrel, and finally what your loaded neck diameter is so we know how much neck tension you have. Non-honed Forster FL sizing dies are known to excessively squeeze the neck down way too much. This is so the die works with all types of brass...

 

[spife7980]

Also, did you take proper measurements to determine your mandrel? Or just got what you read. Take a piece of fired brass, measure the neck, write that number down... Now size the case in your Forster FL Sizing die and measure the neck and write that number down... Now run that case in your mandrel and measure the neck once last time and write that number down... Now seat a bullet in this case and measure the neck one last time and write that number down.

Now take your once fired brass neck measurement and subtract the Forster FL sized neck measurement. This tells you/us how much you are squeezing the neck down from fired.

Now take the final number from above and subtract the number you got when you measured the neck after mandrel.. This tells us how much you are opening the neck back up after sizing with the Forster FL sizing die.

Now take final number from the above question and subtract the number you got when measuring a loaded case neck. This number tells us how much neck tension you have...


This will tell you how much your squeezing your neck down from fired with the Forster, how much your opening it back up with the mandrel, and finally what your loaded neck diameter is so we know how much neck tension you have. Non-honed Forster FL sizing dies are known to excessively squeeze the neck down way too much. This is so the die works with all types of brass...

Just to illustrate the fired, sized, expanded, seated neck diameters

 

[Kaldor]

Thanks, this is very helpful. The purpose of the wet tumble for me is partly to get rid of the lube, and partly to hopefully wash some of the lead away some I'm not spraying lead residue all over my space during the dry tumble. I would guess a dry tumble is just as good at removing the wet lube from sizing, maybe reducing the life of the dry media a little? And when you say you 3-way trim at the end - do you chamfer, then mandrel, then trim and chamfer/deburr again?

On that note - any recommendations for a trimmer? I've had the Lyman Universal Case Trimmer Kit with 9 Pilots on my "to buy" list for a long time, but I wonder if there are any better-liked options out there on the lower-end of the price range.

That's good information on the annealing too - I didn't realize it was so critical. What is the exactly-$300 option you were thinking of? It's possible I could attempt to cobble a DIY setup together, though sometimes that ends up being more expensive than buying the right thing in the first place.

Wet tumbling shouldn't have any issues removing sizing lube unless you're using an excessive amount, and will obviously make the lead a non issue. The lead and dust is why I will never dry tumble again. I wet tumble 1 hour, then let the brass air dry. If you are in a hurry? Throw the brass on a sheet pan and throw it in the oven at 200 degrees for 15 minutes. It wont hurt the brass at all.

Some trimmers have the ability to trim/chamfer/deburr in a single pass. They are generally more expensive and can be onerous to setup when changing calibers. I changed my Giraud to a flat blade exactly because of this.

I have that Lyman trimmer. Its fine for what it is. It will give you a square accurate cut. I use it for oddball stuff I dont have the insert for my Giraud, which is generally low volume hunting ammo in my case. If you plan on doing more than 50 rounds with it, the powered attachment to drive it is probably worth it.

Annealing? You have to look pretty hard to find info out there that says it doesnt work, unless you are making huge mistakes while doing it. I can name several options for gas annealers that work quite well. EP 2.0 is $240, Ugly is $280, Annealeez is $310, Burstfire is $290, AGS is $310. Ive owned the Annealeez, and now use an AGS that I setup with a case feeder. I have friends with a Burstfire, and an Ugly, they work as well. The EP is dead simple. The only thing I can say about annealing? Use a 20# tank to run the torch. The mysteries of annealing are no longer some black art. As far as case life? I would say annealing doubles your case life, and if youre buying brass at $1-2 a pop, doubling your case life easily pays the $300ish for an annealer.

 

[JerkyFreak]

Provided you keep track of the amount of firings and never mix them, you can get away without annealing for quite a few times with no affect on precision.

Chamfering is more important for precision on the short term. Shaving bits off the bullet on seating is more detrimental than a work-harderned piece of brass.

Trimming is a bit more important from a safety point of view. Depending on the headspace you size to, you should trim at least every 3 firings (3 thou headspace).

 

[straightshooter1]

Thanks, this is very helpful. The purpose of the wet tumble for me is partly to get rid of the lube, and partly to hopefully wash some of the lead away some I'm not spraying lead residue all over my space during the dry tumble.

. . . therefore, wet tumbling the very first thing before sizing make sense, AND. . . the outside of the brass is nice and clean so that your lubing is more effective for sizing.

I would guess a dry tumble is just as good at removing the wet lube from sizing, maybe reducing the life of the dry media a little?

Yes, dry tumbling works just fine at removing the lube.

BTW: when expanding your necks with a mandrel, you should need any lube. . . especially if the mouths have been chamfered at some point.

And when you say you 3-way trim at the end - do you chamfer, then mandrel, then trim and chamfer/deburr again?

I use a 3-way trimmer that trims, chamfers and deburrs all at the same time. There are various 3-way cutting heads available and I think Forster sells one.

On that note - any recommendations for a trimmer? I've had the Lyman Universal Case Trimmer Kit with 9 Pilots on my "to buy" list for a long time, but I wonder if there are any better-liked options out there on the lower-end of the price range.

That Layman tool can work just fine and I think they can be found for under $100. Trimming with a hand tool can be a chore. But set it up to be driven with cordless drill can make it easier.

While I don't use this type of 3-way cutter, here that Forster one is like:

https://shop.natchezss.com/reloading/tools-gauges/case-prep-tools/3-in-1-case-mouth-cutter-with-264-pilot-for-65mm-fp3cut264?srsltid=AfmBOopp5Re0SkOMGMaoFXSzCwA32nC_zREYcijLjKuGjwAorF91bcIdeqs

That's good information on the annealing too - I didn't realize it was so critical. What is the exactly-$300 option you were thinking of? It's possible I could attempt to cobble a DIY setup together, though sometimes that ends up being more expensive than buying the right thing in the first place.

I wouldn't say annealing is so "critical" as there are other ways to achieve some of the same results. Like having custom cut chambers and custom sizing dies to reduce the amount of movement the brass goes through in the cycle of firing and sizing, which makes for less work hardening of the brass. Annealing is the easy button for most.

For those priced under $300:

AGS Annealer

Amazon.com

Ugly Annealer

Amazon.com

Burstfire Annealer combo

Amazon.com

The Burstfire might be a good fit for you as it has a case prep station built into it that you can use for chamfering and deburring. . . ??? . . . though I'm not a particular fan of such prep stations.