Adjusting neck tension when using mandrels

[goosepilot]

So I'm relatively inexperienced reloader. Early on using redding bushing sizes, I got tapered necks. Ran across the sinclair expanding mandrel and have been using it for 5 ish years.

Now I just got into 600-1k yard bench shooting and bought a 6mm dasher from a guy retiring from shooting. So I thought I would test neck tension adjustments, but no one seems to make any mandrels less than .240. Depending on brass, I'm getting. 015-.025 neck tension.

Cortina's company responded to my email saying to adjust bushing size. To it seems like I should adjust mandrel size. I do use amp annealer each firing. I ordered more smaller sizes of bushings but they haven't arrived yet.

Was just curious what others who use expander mandrels do to adjust neck tension?

 

[ChrisNZ]

Maybe you could get a machinist to make you a custom one?

 

[ELR LVR]

You say youre getting .015 to .025 neck tension???????
You sure you're reading your measurement device correctly?
Do you mean .0015" to .0025" ???
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If you want less neck tension:
1) With bushings you can trim the OD necks of the brass
when you neck size it will only squeeze down so much right?
So if your necks are .010 thick, and you trim them down to .009
you will size the neck tension down less internally on the ID
If you want to keep your neck thickness the same then you'd have to have a custom bushing made if its not offered commercially
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More neck tension
2) Spin your mandrel down with sandpaper or diamond stone if you want tighter neck tension
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I have not tried this myself yet but I've heard some guys have flipped their bushing over and it is lightly less on one side, tighter on the other. ---Likely a dif of 0.0005" (half a thou)

 

[RussellJ]

So I'm relatively inexperienced reloader. Early on using redding bushing sizes, I got tapered necks. Ran across the sinclair expanding mandrel and have been using it for 5 ish years.

Now I just got into 600-1k yard bench shooting and bought a 6mm dasher from a guy retiring from shooting. So I thought I would test neck tension adjustments, but no one seems to make any mandrels less than .240. Depending on brass, I'm getting. 015-.025 neck tension.

Cortina's company responded to my email saying to adjust bushing size. To it seems like I should adjust mandrel size. I do use amp annealer each firing. I ordered more smaller sizes of bushings but they haven't arrived yet.

Was just curious what others who use expander mandrels do to adjust neck tension?

Here is a some really good information on a Porter mandrel setup. I own one and really like it. Takes standard ER style collets and Pin Gages. Pin Gages are available from McMaster Carr, MSC Direct, ebay, etc.

The ultimate solution to neck tension

I know that everyone likes to control neck tension with bushings but to me that doesn't seem like a very good way. From my way of thinking bushings transfer any variance in neck thickness to the inside of the neck where they have a direct impact on neck tension. That is not a good thing, because...

forum.accurateshooter.com

 

[ELR LVR]

Here is a some really good information on a Porter mandrel setup. I own one and really like it. Takes standard ER style collets and Pin Gages. Pin Gages are available from McMaster Carr, MSC Direct, ebay, etc.

The ultimate solution to neck tension

I know that everyone likes to control neck tension with bushings but to me that doesn't seem like a very good way. From my way of thinking bushings transfer any variance in neck thickness to the inside of the neck where they have a direct impact on neck tension. That is not a good thing, because...

forum.accurateshooter.com

Forget what I said, that set up is just all sorts of Bad assery right there!

 

[243winxb]

Was just curious what others who use expander mandrels do to adjust neck tension?

Outside neck turning would seem to be #1, on the to do list. Goes with full benchrest prep of the brass.

Then, deal with springback.
I dont use mandrels.

 

[goosepilot]

My bad, yes .0015-.0025

I'm not talking about custom bushings, I'm talking about expander mandrels after the bushing as the final neck tension setting step.

I can see the neck springing back .001 after the mandrel, I'm just having a hard time seeing a smaller bushing increasing that spring back to .002 or .003 or .004 when using the same expander

 

[ELR LVR]

My bad, yes .0015-.0025

I'm not talking about custom bushings, I'm talking about expander mandrels after the bushing as the final neck tension setting step.

I can see the neck springing back .001 after the mandrel, I'm just having a hard time seeing a smaller bushing increasing that spring back to .002 or .003 or .004 when using the same expander

no, you'd use the custom size bushing only to size down to whatever internal dia. you want
done.
... no expanding after.... since you are already at final dimension
---Also another reason for neck turning, so when you size the neck down the ID stays concentric

 

[JFrank]

My bad, yes .0015-.0025

I'm not talking about custom bushings, I'm talking about expander mandrels after the bushing as the final neck tension setting step.

I can see the neck springing back .001 after the mandrel, I'm just having a hard time seeing a smaller bushing increasing that spring back to .002 or .003 or .004 when using the same expander

Mandel is an option but not a necessity, spring back imo is a non factor, turned necks or no turn neck, many LR guys just measure the neck OD of a loaded round and subtract .002 -.005 and order those four bushing and test each one side by side and let the target show you the path forward.
Personally I like a tapered Wilson bushing.

Jim

 

[RED DIRT]

I no longer use mandrels. I never benefitted much from them, other than a much lighter wallet after everything was bought. Like what JFrank said above, is how i do it now. K.I.S.S.

 

[6.5 forever]

Hey guys, I thought the mandrel also helped push doughnuts back out?

 

[wkdickinson]

The issue for me with adjusting neck tension using just bushing size, is the necks need to be a consistent thickness, which requires neck turning. I hate neck turning! Finish sizing with a mandrel pushes any variance in neck thickness to the outside, which IMHO is meaningless with a "no turn" chamber.

 

[Straightshooter1]

Hey guys, I thought the mandrel also helped push doughnuts back out?

Absolutely does, though less so with work hardened cases from several firings, due to springback.

I've verified this using my pin gauges on my cases that I anneal after every firing. Before running my mandrel through the necks, I ran a pin gauge into the neck to measure the ID of the neck and it wouldn't go past the donut. Measured the ID where the donut was, there was a .0025 difference (these are Lapua cases fired 16 times). After running my mandrel through the neck to get the "neck tension" I'm after, the snug fitting pin gauge would run all the way through the neck with the donut not hindering it at all. The donut had been moved to the outside as a difference in OD could now be measured on the neck at the neck-shoulder junction.

 

[Straightshooter1]

The issue for me with adjusting neck tension using just bushing size, is the necks need to be a consistent thickness, which requires neck turning. I hate neck turning! Finish sizing with a mandrel pushes any variance in neck thickness to the outside, which IMHO is meaningless with a "no turn" chamber.

Hmmmm??? Not really "meaningless" for no turn chambers. While much of the variance in neck thickness can be move to the outside for a more uniform ID, there's still an imbalance in interference that variance applies to the seated bullet, resulting in the bullet nor the blowby being released uniformly. The bigger issue is for any bullets being seated deep enough for the bearing surface to be in contact with the donut that develops.

 

[6.5 forever]

Absolutely does, though less so with work hardened cases from several firings, due to springback.

I've verified this using my pin gauges on my cases that I anneal after every firing. Before running my mandrel through the necks, I ran a pin gauge into the neck to measure the ID of the neck and it wouldn't go past the donut. Measured the ID where the donut was, there was a .0025 difference (these are Lapua cases fired 16 times). After running my mandrel through the neck to get the "neck tension" I'm after, the snug fitting pin gauge would run all the way through the neck with the donut not hindering it at all. The donut had be move to the outside as a difference in OD could now be measured on the neck at the neck-shoulder junction.

My experience exactly!

 

[bks22345]

I watched a podcast with Erik where he stated he adjusted neck tension with his bushings, even though he used the same mandrel. The thought that a tighter neck would spring back to a different diameter, even with the same mandrel. I think k it was the one with Sellers on tuners.

 

[JMayo]

Don't let the brass hit the bare bench & don't let it hit the ground.
Bushing size only.

 

[Bottom Fodder]

Maybe talk to the guy you bought it from and see what he used, he might sell his dies and just maybe give his load data

 

[Webster]

So I'm relatively inexperienced reloader. Early on using redding bushing sizes, I got tapered necks. Ran across the sinclair expanding mandrel and have been using it for 5 ish years.

Now I just got into 600-1k yard bench shooting and bought a 6mm dasher from a guy retiring from shooting. So I thought I would test neck tension adjustments, but no one seems to make any mandrels less than .240. Depending on brass, I'm getting. 015-.025 neck tension.

Cortina's company responded to my email saying to adjust bushing size. To it seems like I should adjust mandrel size. I do use amp annealer each firing. I ordered more smaller sizes of bushings but they haven't arrived yet.

Was just curious what others who use expander mandrels do to adjust neck tension?

Bushing dies only size the first half of the neck. That should mean the mandrel only sizes the smaller first half of the neck. In Erik Cortina's video he used a bushing die and and mandrel. His comments would be interesting. I would think 0.0015-.0025" is the range every agrees on. Smaller mandrel you would get zero tension?

 

[Chris Edmondson]

Here's a link to Short Action Customs Bushing and Mandrel calculator: https://shortactioncustoms.com/product/modular-sizing-die-creedmoor/

You decide if you want to use a mandrel or not, enter your desired neck tension and bullet diameter, enter either your neck wall thickness or loaded round neck diameter, press Calculate. The result will suggest a suitable bushing and mandrel, or just the bushing if don't want to use a mandrel. There are individual variables which may affect the ultimate accuracy of the result, but its a good place to start. Good luck with your rifle .