What is the purpose of using a expander mandrel after full length neck sizing with a bushing. I thought once you used the neck bushing you had the neck where you wanted it for seating a bullet with your desired neck tension. What diameter of mandrel would you need to use. For example using a .324 bushing what and why would you use a expanding mandrel. I am confused and can I get it explained at the 1st grade level or even pre-school (LOL).
Mandrel sizing after full length neck sizing
- Thread starter 46490
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It's actually a pretty simple issue to understand. Even a 1st grader should be able to understand???
Anyway . . . when you have necks with thickness variance around the diameter, the action of an expander mandrel uniforms the interior diameter, which helps with keeping a seated bullet runout low. A bushing sizing die does just the opposite; uniforming the outside diameter of the neck and the unevenness of the neck thickness is moved inside causing more runout on a seated bullet.
If necks are turned to a uniform thickness, then it doesn't really matter much which is used if one has good bushing dies, as bushing dies tend to induce more neck runout than the use of expander mandrels.
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The Lyman mandrels that I have can be adjusted so that it puts a tiny flare in the top ten thousands or so of the neck making it easier to seat bullets straight.
Similar to what an expander die does in a pistol case.
Similar to what an expander die does in a pistol case.
Of course, if you use standard calibers, the answer is the Lee Collet Die - one pass with a degree of centering of the process, compared to two or more opportunities to create runout with one or more bushings followed by an expander.
Some of us subscribe to the notion that the most consistent neck tension is created when the last operation on the neck is expansion. I also use the Lee Collet Die following full-sizing with a Wilson bushing die. The Lee Collet die has fingers that press the neck wall against a mandrel that is aligned with the flash hole. Because of that, I believe it creates concentric ammo. When I do my part, I get completed cartridges with runout at or below .001 inch.
wkdickinson
Gold $$ Contributor
For me, using a mandrel as the final step in the case sizing process, allows for a consistent neck tension, without neck turning (I hate neck turning). I use a FL bushing die to undersize the neck by 3-4 thousandths, then expand them with a mandrel to result in about .001 neck tension.
RegionRat
Gold $$ Contributor
While I am a long time Lee Collet Die user, I will add that it doesn't size the body, so you still end up with another operation for shoulder and body bump.
One aspect of a mandrel is it can be a two step diameter..... where the business end,is larger than towards the shoulder. Can't be done sizing from outside,bushing or conventional.
On a stepped mandrel you can also have a flare above the second step... if you need it for cast. One advantage of a step is in alignment of the bullet before seating. Instead of just sitting/balancing the bullet on top of the case, hoping everything goes well during seating..... with the step,the bullet goes in the case a smidge(moreso than just a flair).
I make spuds(mandrels)for Lyman M dies,and make seater dies...along with seater stems. Don't want to sound preachy but,I just don't trust a seater stem(or die) to correct any misalignment. It is especially easy to test. Now admittedly,it's a bigger problem with cast but;
Once that bullet starts it's journey into the case neck during seating op,that initial cpl thousandths sets the angle in stone. Or at least,has a very strong influence. Once I started concentrating on getting very low runout,before seating..... finished rounds come out durn near perfect. Tough for me to put into words. Could show you in under 30 seconds.
Custom spuds are stupid easy to make on a lathe. Their "finish" is another interesting,almost can of worms. Smoother,finer finish isn't the panacea logic would indicate. Make a cpl,testing the final finish....
On a stepped mandrel you can also have a flare above the second step... if you need it for cast. One advantage of a step is in alignment of the bullet before seating. Instead of just sitting/balancing the bullet on top of the case, hoping everything goes well during seating..... with the step,the bullet goes in the case a smidge(moreso than just a flair).
I make spuds(mandrels)for Lyman M dies,and make seater dies...along with seater stems. Don't want to sound preachy but,I just don't trust a seater stem(or die) to correct any misalignment. It is especially easy to test. Now admittedly,it's a bigger problem with cast but;
Once that bullet starts it's journey into the case neck during seating op,that initial cpl thousandths sets the angle in stone. Or at least,has a very strong influence. Once I started concentrating on getting very low runout,before seating..... finished rounds come out durn near perfect. Tough for me to put into words. Could show you in under 30 seconds.
Custom spuds are stupid easy to make on a lathe. Their "finish" is another interesting,almost can of worms. Smoother,finer finish isn't the panacea logic would indicate. Make a cpl,testing the final finish....
Very good info here. One of my best mandrels, with a mirror finish, would stick with the best of them! Ended up under cutting the back half of the mandrel and it then worked great ! Live and learn.
Paul
Right,what's happening is folks need to realize that in a swaging op such as this,you could have turned slots cut in the spud,the ones doing the "work" are the major diameter sections. Not too dissimilar from fluting a bolt.
Polishing is a tricky bit. Yes it will reduce friction,up to a point.... then it increases. Further,the tiny "valleys" left in a slightly rougher spud.... carry's and holds any lube. If the thing is too perfect,the lube gets wiped off on the first use.
So easy to make. And one way is;
Say you wanted a custom sized 6.5..... buy a 7mm. You're about 90% there.
Polishing is a tricky bit. Yes it will reduce friction,up to a point.... then it increases. Further,the tiny "valleys" left in a slightly rougher spud.... carry's and holds any lube. If the thing is too perfect,the lube gets wiped off on the first use.
So easy to make. And one way is;
Say you wanted a custom sized 6.5..... buy a 7mm. You're about 90% there.
How important is the mandrel centering with the decapping pin? I broke off the pin on mine because I wanted to use it with primed brass to uniform necks. I was tempted to break off the pin in my 6.5 LCD also because it’s too big for small flash holes. I filed it down instead but it seems not to matter.
For just those occasions, I cut off a measured amount that will guarantee that the pin won't touch the anvil off all my collet mandrels and radius the tip as needed.
NZ_Fclass
Silver $$ Contributor
The Lee collet is a good tool - provided that you want the neck tension set by Mr Lee!
The mandrel in the .243 die is .241, which I find too thin - I use a 243 mandrel, which after springback gives me 2 thou tension.
Another option I found favorable is to not use a mandrel at all. I really think light NT as well as working brass back and forth can be detrimental and create a load that is touchy to maintain a tune. The more I test bullet hold the evidence seems clear that the rifle will let you know what the preference is.
I know it sounds cool to only have .001 or .002.5 neck tension whatever but new re loader's should learn to test for themselves starting with plenty ..
I know it sounds cool to only have .001 or .002.5 neck tension whatever but new re loader's should learn to test for themselves starting with plenty ..
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Coyotefurharvester
Silver $$ Contributor
I think brass composition(and thickness) makes a difference on how much neck interference you can get away with accuracy wise. Softer brass(and thinner) will allow smaller I.D. necks, as the bullet can expand the neck without damage to the jacket. Same for bullets with "harder" jackets, a tight neck will open without accuracy affecting damage.
Lee offers affordable oversized mandrels. The default value is -0.002” from bullet diameter.
NZ_Fclass
Silver $$ Contributor
I did not know that. I have certainly never seen them in my part of the globe - and the postage from the US would be very high.
skeeljc
Gold $$ Contributor
I have a Forster FL sizing die that has the neck opened up to .245" diameter (.223 Remington). It will produce FL sized cased (no expander) with neck runout less than .001" t.i.r. I can tweak the I.D. with a mandrell by a couple of thousands without adding to the runout.
I use this same approach, only my Forster is honed to 0.2445. The factory Forster neck is much too small.
I just sized a batch of brass using Forster+mandrel and I’m going to compare it to LCD+ Redding body die
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