Mandrel Musings

Rocketmandb

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    When I first got my K&M arbor press for seating, I was somewhat surprised at the spread of the values of force required to seat bullets. Knowing that neck tension plays a significant role in ES/SD, I started doing various things to try to bring seating force in line. I had been doing most my work with the arbor press with my 300 PRC because I had it only for a limited time while I had my 6 CM, and when I got my 6 BRA, LE Wilson did not yet have a seating die for it.

    With my 300, I would see a seating force in the 40-50 lb range. Anything out that range I'd mark and use as foulers/cold bore rounds, etc. That would end up being about 1 out of 10 rounds.

    When LE Wilson came out with their 6 BRA seater and I began using it with the same techniques I had been using on my 300. Immediately I noticed how much more consistent the seating force was on the smaller round - many times I will only get like 1 out of 50 or 1 out of 100 that fall outside a 10 lb range. Now, you'd possibly expect this because of the smaller round, but the difference was so pronounced that I didn't believe it could be solely due to this. I believe I know why, but I'm going to wait until I test to mention it.

    So, I decided to start doing some testing to both measure the effects of using the mandrel/neck lube as well as to perfect it further.

    The first test was performed today and it was to test the impact of using a mandrel vs. not. To do this, I loaded 10 rounds using my standard process, which includes using graphite neck lube and a mandrel after sizing. I then loaded another 10 rounds, keeping all the steps the same, except that I skipped the mandrel step - neck lube was still applied.

    EDIT: Equipment/components Used
    - Lapua 6 BR Brass formed to 6 BRA
    - .265 neck bushing in sizing die
    - .240 mandrel size
    - LE Wilson 6 BRA seating die
    - Brass annealed prior to sizing

    Here are the seating forces of the non-standard (no mandrel) rounds:

    55 lb
    38
    45
    27
    52
    60
    35
    62
    32
    42
    SD: 11.5 lb

    Here are the seating forces of the standard (mandrel) rounds:

    27 lb
    23
    23
    22
    23
    22
    26
    24
    22
    24
    SD: 1.6 lb
    Note: I also loaded a further 30 rounds using this process and all fell within the range shown here. Also, the neck bushing is very closely matched to the mandrel.

    Out at the range, I measured the muzzle velocity of each group. Note that the order of firing does not necessarily match the order of loading - I should have.

    Standard:
    2987
    2980
    2980
    2973
    2981
    2970
    2980
    2981
    2983
    2967
    SD: 5.88 fps
    ES: 20
    Note: It was significantly warmer today than anticipated, and muzzle velocities were on the order of 30 fps faster than normal. I believe this pushed the SD from my normal mid-4s to the nearly 6 exhibited here.


    Non-standard:
    2969
    2990
    3000
    2988
    2988
    2988
    2988
    2984
    2999
    2977
    SD: 8.7 fps
    ES: 31
    Note: Yes, I actually did have 4 shots in a row at 2988 fps. I first thought the Labradar was stuck.

    Conclusion: Even with the small sample size, it's clear that the the consistent neck tension group exhibited meaningful decreases in SD.

    Next steps:

    1) Testing no mandrel, no lube vs. standard
    2) Testing different bushing sizes on my 300 - try to match as close to the mandrel as possible - and compare to the current, which is currently a fair amount smaller than the mandrel
     
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    Mauser06

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    Guess I am confused.


    Can you share detail of what dies and bushings were used for the 2 tests?


    Your results definitely seem to show consistency.
     

    Rocketmandb

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    Guess I am confused.


    Can you share detail of what dies and bushings were used for the 2 tests?


    Your results definitely seem to show consistency.

    I should have added that in. I edited my post and added the equipment used.

    As for the bushings, it was the same bushing for both (.265). This yielded what I perceived as the minimal forced when using the mandrel. The .266 I felt caused a few cases to not be opened at all.

    On my 300, I think the bushing I'm currently using is too small. This means the brass has to be opened more by the mandrel, and thus has more propensity to spring back, and by differing amounts based on case wall thickness. This is why I'm going to test bushing size on that one as one of the next tests.
     
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    Mauser06

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    Thanx! Wasn't 100% sure if you were using bushing dies for both tests or what. Definitely looking forward to hearing more. Appreciate guys sharing their tests. Always interesting to see what other guys come up with. And being new to the precision game, it's helpful to make informed decisions and fine tuning it to my particular needs etc.
     

    iceng

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    This was a fantastic experiment. Tagging in to learn more as you post results.

    What bushings vs neck thickness did you select ? You said 265 as it still allowed the mandrel to expand, and 266 seemed too large. What was your neck thickness ? What mandrel size ? 21st century ?

    Nice work.
     

    Mauser06

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    Thinking outloud.....I guess this kinda disproves "the bullet is the mandrel" theory....?


    One which I subscribe to....lol. but have been looking to utilize my 550 for brass prep and considering running a mandrel.
     

    Alan Warner

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    I should have added that in. I edited my post and added the equipment used.

    As for the bushings, it was the same bushing for both (.265). This yielded what I perceived as the minimal forced when using the mandrel. The .266 I felt caused a few cases to not be opened at all.

    On my 300, I think the bushing I'm currently using is too small. This means the brass has to be opened more by the mandrel, and thus has more propensity to spring back, and by differing amounts based on case wall thickness. This is why I'm going to test bushing size on that one as one of the next tests.
    Very nice work!
    May I suggest culling the one(s) that seemed not expanded , maybe use a bushing .001 smaller on those in order to get a similar amount of expansion.
    Forming of metal always has an amount of springback and that amount
    Is directly dependent on the starting/ending points dimensionally .
     

    SicVic

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    I really like reading when comparisons like this are made.
    This is why I reload. Build, test, ponder, modify and repeat. I never want to find the perfect load cause what would I do then???
    I'm a fan of the Mandrels and for me they provide the results I'm happy with.

    Neck tension is funny.
    You can have .0005" tension press at 55# or .003" tension press at 30#.
    Your style of case Prep will dictate.
    I've posted this video here before but it plays closely to what you're experimenting with now.
    Not meant to be taken too seriously just more of a fun comparison.
    I'll continue to follow to see how you future tests turn out.

     

    Rocketmandb

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    Very nice work!
    May I suggest culling the one(s) that seemed not expanded , maybe use a bushing .001 smaller on those in order to get a similar amount of expansion.
    Forming of metal always has an amount of springback and that amount
    Is directly dependent on the starting/ending points dimensionally .

    Just to be clear on this one, all the shots in this test were done with the .265 bushing. I had played around with the .266 before, but moved to the .265 because it did not seem like the .266 allowed the mandrel to engage every case due to irregularities case to case with neck wall thickness. The .265 allowed the mandrel to engage the neck on every case.
     

    Rocketmandb

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    Anneal your brass properly, use the right bushing you can control neck tension with minimal runout on the loaded round.

    If you neck turn, yes. Most people, me included, do not neck turn, though I'm considering it. Using a mandrel is a way to partially normalize for inconsistent neck thickness.
     

    Rocketmandb

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    Neck tension is funny.
    You can have .0005" tension press at 55# or .003" tension press at 30#.

    If you're talking seating force (the 55# or 30#) you reference, that is related to one or both of the following:

    - Friction inside the neck
    - Force exhibited from the walls of the neck onto the bullet surface

    The force is related to:
    - The size of the neck vs the bullet
    - The amount of elasticity in the brass

    Using a mandrel helps normalize one of the items (size), neck lube helps normalize another (friction), and annealing helps normalize the last (elasticity)
     
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    Rocketmandb

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    This was a fantastic experiment. Tagging in to learn more as you post results.

    What bushings vs neck thickness did you select ? You said 265 as it still allowed the mandrel to expand, and 266 seemed too large. What was your neck thickness ? What mandrel size ? 21st century ?

    Nice work.

    The brass measures .267 to .2685 after a bullet (.243) is loaded, so using a .266 with the spring back I think some were right at the edge of engaging the mandrel. Of course, I have no way of knowing for sure since there is no force gauge on the main press.

    The mandrel is .240 and is Sinclair - I use the 21st Century on my 300.
     
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    Rocketmandb

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    Thinking outloud.....I guess this kinda disproves "the bullet is the mandrel" theory....?

    If you neck turn, then using a mandrel is dramatically diminished in its effect, so that theory holds true. If you don't neck turn, then you're getting varied force being applied against the bullet due to differing interior neck sizes.

    I intuitively knew this, but after having a few people challenge it, I decided to prove it. But also, there's this big difference in consistency I have between my 300 and the 6 on seating force.

    There are two differences between the two: one, obviously, is the size of the bullet/case, the other is that I currently use a relatively smaller bushing on my 300, which means the neck is getting sized down more (relatively) before I use the mandrel. Why do I do this? Honestly, I've been lazy. This next test will determine whether that inconsistency is simply due to being a bigger/different case or if getting the neck size as close as possible to the mandrel size will make a difference.
     

    Criver600

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    If you neck turn, yes. Most people, me included, do not neck turn, though I'm considering it. Using a mandrel is a way to partially normalize for inconsistent neck thickness.
    Nope, anneal your brass for consistent elasticity, bushing choice you control your seating pressure.
    I have and use "tight-neck" reamers, I neck turn for these, for a factory chamber its a waste of time. I anneal and run my neck bushing of choice.
     

    Rocketmandb

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    Nope, anneal your brass for consistent elasticity, bushing choice you control your seating pressure.
    I have and use "tight-neck" reamers, I neck turn for these, for a factory chamber its a waste of time. I anneal and run my neck bushing of choice.

    So you're saying that if you have different neck thicknesses between brass you're using that it makes no difference?

    Whoa, so wrong it doesn't warrant a response.
     

    918v

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    So you're saying that if you have different neck thicknesses between brass you're using that it makes no difference?

    Whoa, so wrong it doesn't warrant a response.

    Some people anneal their necks to the point they so soft it doesn’t make a difference.
     

    Rocketmandb

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    Some people anneal their necks to the point they so soft it doesn’t make a difference.

    I suppose if you take it to the point where you can crush it between your fingers, then sure. No spring back, no neck tension.
     

    Criver600

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    So you're saying that if you have different neck thicknesses between brass you're using that it makes no difference?

    Whoa, so wrong it doesn't warrant a response.
    0.0015, difference in neck thickness not enough to matter. Neck turning is all about fitment using "tight neck chambers". If your brass has over 0.002 wall runout give it to someone you don't like:)
    Your woofin about undersizing your necks then uniforming with a mandrel. Whatever you want to do tickles the shit out of me. BUT a standard neck sizing die does what? Undersizes your cartridge neck then pulls a nominally sized expander ball back through the neck. I'm saying anneal for consistent brass elasticity and size with the bushing of choice, you will have your consistant seating pressure. I won a K&M arbor press with the force attachment at the IBS 1000 yard nationals at Thunder Valley Ohio twenty years ago and have been down that rabbit hole.
     

    Rocketmandb

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    0.0015, difference in neck thickness not enough to matter.

    I just measured the difference. I agree with you on annealing, we'll continue to disagree on the rest. Thanks for your input though.
     

    918v

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    Annealing by itself does not improve the consistency of seating pressure. Brass cases do not harden at different rates. They all harden at the same rate if you keep track of the number of firings. Within a certain lot of brass you’ll find some cases have softer necks than others. If you anneal the whole lot the cases which were softer than the rest will still be softer than the rest. All you did by annealing is decrease the hardness of the whole lot but the individual cases will still differ in hardness, largely due to weight variance.

    If you sort the cases by weight after turning the necks and uniforming the primer pockets you stand a better chance of achieving uniform hardness through annealing. Then you will have a more consistent seating pressure.
     

    ceekay1

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    The only thing surprising to me about the OP's numbers is that the SD number for the non-mandrel group wasn't much higher. Those 4 in a row at 2988fps with the non-mandrel rounds is a crazy coincidence that more than likely would never end up like that again.

    Almost warrants another test... but no need to waste components on something most of us already know: mandrel = good. I think the 11.5lbs vs 1.6lbs at the handle when seating bullets tells the tale.

    Yes, we know seating pressure is a good part friction and doesn't exactly quantify neck tension... but it ain't necessarily wrong either. More consistent is more consistent, and usually better, and it must do something good because it's easy to see the results down range.
     
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    Rocketmandb

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    The only thing surprising to me about the OP's numbers is that the SD number for the non-mandrel group wasn't much higher. Those 4 in a row at 2988fps with the non-mandrel rounds is a crazy coincidence that more than likely would never end up like that again.

    I was actually expecting something around 3, so this was close. But yes, those 4 in a row is something I almost never see and certainly lowered it. Honestly, I'm more surprised at how low the SD was on the seating force of my standard ones - I mentioned this earlier, but among the 40 standard rounds (the+30 beyond the 10 measured), all fell within the range I list here. It is this high consistency that I've been seeing in the last few hundred loads I've done that prompted me to start testing things - primarily because my 300 rounds don't show nearly the same.

    Almost warrants another test... but no need to waste components on something most of us already know: mandrel = good. I think the 11.5lbs vs 1.6lbs at the handle when seating bullets tells the tale.

    I will be running another, but this time no neck lube - what's the over-under on the SD for both the seating force and velocity? I might run another set identical to this one to see how it plays. This time I'll mark the rounds with the seating force so I can tie the two together. It will be interesting to see what correlation (if any) exists.

    Yes, we know seating pressure is a good part friction and doesn't exactly quantify neck tension... but it ain't necessarily wrong either. More consistent is more consistent, and usually better, and it must do something good because it's easy to see the results down range.

    I've always said that these two steps (lube + mandrel) brought me the most significant improvement of any steps I've added. Now I'm measuring it.
     

    Joel Danielson

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    Something else that may be interesting to add to the test would be to see what happens with rounds that have sat loaded for a week + vs ones fresh loaded within the past 24 hours to see what es and sd are. I seat everything long if making rounds for a match that is more than 2 days out. When in a f-class or bench match over several days, rounds for the next day are adjusted for proper jump the night before.
    Cheers
     
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    Rocketmandb

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    Something else that may be interesting to add to the test would be to see what happens with rounds that have sat loaded for a week + vs ones fresh loaded within the past 24 hours. I seat everything long if making rounds for a match that is more than 2 days out. When in a f-class or bench match over several days, rounds for the next day are seated the night before.
    Cheers

    Well, as it happens, I only fired 25 out of the 50 rounds I loaded (5 foulers + the 10 of each type referenced here). I went to the private range with @BFuller and he had just gotten his new 300 PRC, so we spent the majority of time messing with that. I'm probably not going to shoot again for about 3 weeks, so they can be a de facto test.
     
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    ceekay1

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    Something else that may be interesting to add to the test would be to see what happens with rounds that have sat loaded for a week + vs ones fresh loaded within the past 24 hours to see what es and sd are. I seat everything long if making rounds for a match that is more than 2 days out. When in a f-class or bench match over several days, rounds for the next day are adjusted for proper jump the night before.
    Cheers

    I feel like there's something to this.^^^

    I tend to load in batches of 100rds or 200rds at a time, but I usually only shoot 50rds per range visit... and I've noticed that when I first hit the range with my first 50 of a new batch (that are usually only 24-73 hours old) they're pretty much always awesome.

    On subsequent trips, the other rounds that were seated/completed on that same day as the first 50 (but not shot until later by a couple days or sometimes a week or more) are still good, but maybe just not quite as good..?

    I've been shooting out to a 1000 yards more regularly lately and feel like I definitely can see a difference. Why? IDK, but I'm kind of leaning towards thinking fresh rounds are best...
     

    Joel Danielson

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    I feel like there's something to this.^^^

    I tend to load in batches of 100rds or 200rds at a time, but I usually only shoot 50rds per range visit... and I've noticed that when I first hit the range with my first 50 of a new batch (that are usually only 24-73 hours old) they're pretty much always awesome.

    On subsequent trips, the other rounds that were seated/completed on that same day as the first 50 (but not shot until later by a couple days or sometimes a week or more) are still good, but maybe just not quite as good..?

    I've been shooting out to a 1000 yards more regularly lately and feel like I definitely can see a difference. Why? IDK, but I'm kind of leaning towards thinking fresh rounds are best...
    When you go back in to re-seat the bullets for the next day matches, you will see or feel the differences in seating pressure all over again. I will move rounds around in my case for the sequence of firing based on how the seating pressure is the night before. In a string of fire (22 shots in 22 minutes for f-class), you can have similar seating pressures all together if you have any variations.
    Cheers
     
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    Rocketmandb

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    Are you checking id with pin guages? I would be curious to know if that variance equates to more or less pressure seating. And if so how much.

    Thanks for making more work for me :) I will next time and will record all the stuff.