21st century shooting 7mm expander mandrel diameter

[BradY]

can anyone tell me the actual diameter of a 21st century 7mm expander mandrel with the TiN coating?

 

[Wingzero]

The actual size of their mandrels are not indicated in their website. I ask them their sizes thru email but I never got a response. Is it safe to assume that all expander mandrels (regardless of brand) are .001 less than the bullet diameter and turning mandrels .002 less.

 

[BenPerfected]

K&M Precision Shooting Products will custom make any size expander mandrel in .0005 increments. These mandrels will allow you to select & adjust your neck tension. www.kmshooting.com
Ben

 

[spife7980]

But the K&M are just stainless and you have to lube where as the 21st century you can get coated in the tin and dont have to lube, correct? I was debating this same thing this morning

Is it safe to assume that all expander mandrels (regardless of brand) are .001 less than the bullet diameter and turning mandrels .002 less.

I too would like to know this, if every expander mandrel is .001 less than bullet diameter that would be perfect for .002 bullet tension after brass spring back, correct? (screw off guffey, no one cares to hear your diatribe on tension today)

 

[stgw77]

BradY,
Took measurements today for you, using my Mitutoyo digital tool, with 0.001 mm (milimeters, please do calculations to get inches, not hard at all) resolution.
- 21st century Titanium nitrate Expander mandrel 7 mm: 7.187 mm;
- 21 st century Titanium nitrate Turning arbor 7 mm: 7.159 mm.
Hope it helps you.

 

[rardoin]

(screw off guffey, no one cares to hear your diatribe on tension today)

Preemptive strike......I like it!

 

[spife7980]

BradY,
Took measurements today for you, using my Mitutoyo digital tool, with 0.001 mm (milimeters, please do calculations to get inches, not hard at all) resolution.
- 21st century Titanium nitrate Expander mandrel 7 mm: 7.187 mm;.2829
- 21 st century Titanium nitrate Turning arbor 7 mm: 7.159 mm..2819
Hope it helps you.

So the 7mm expander is .001 less than .284 and the turner is .002 less. Much appreciated

 

[77racer]

I recently bought the die that Joe R has in the picture. I'll never use anything else again. Brass is staying concentric and it makes it so easy to test different amounts of neck tension. Buy a few gauge pins and test away.

 

[spife7980]

I recently bought the die that Joe R has in the picture. I'll never use anything else again. Brass is staying concentric and it makes it so easy to test different amounts of neck tension. Buy a few gauge pins and test away.

I thought that was a custom one off die? I realize the mandrels are from vermont gauge, where did you get the rest of it?

 

[dkhunt14]

But the K&M are just stainless and you have to lube where as the 21st century you can get coated in the tin and dont have to lube, correct? I was debating this same thing this morning



I too would like to know this, if every expander mandrel is .001 less than bullet diameter that would be perfect for .002 bullet tension after brass spring back, correct? (screw off guffey, no one cares to hear your diatribe on tension today)

I wouldn't turn any brass without lube. Lube helps keep heat down. Matt

 

[JRS]

But the K&M are just stainless and you have to lube where as the 21st century you can get coated in the tin and dont have to lube, correct? I was debating this same thing this morning



I too would like to know this, if every expander mandrel is .001 less than bullet diameter that would be perfect for .002 bullet tension after brass spring back, correct? (screw off guffey, no one cares to hear your diatribe on tension today)

K&M provides carbide mandrels also. No matter, the mandrel needs to be lubed.

 

[Petros284]

Hey All
Just talked to John at 21st Century. He has been really busy and has not been at the computer. I just confirmed the measurements above. He stated that "Our 21st century shooting arbors are .2820" for the neck turner mandrel and .2830" for the expander mandrel".

He also said he will machine custom arbors to customer specifications

Thanks

 

[BenPerfected]

And when they're not Roger will tell you that id depends on whose micrometer its used.

If you want a universal expander mandrel die with precision mandrel there is only one. It uses standard Vermont Gage pin gauges that can be bought for $3 on Amazon and they are precise within +/- 0.0002. If you want even more precision the mandrel cost $18 and have to be custom ordered from Vermont Gauge +/-0.000002 and you get a certificate of accuracy with the name of the guy that inspected and when. Not some lame excuse from Roger.


View attachment 1026752

My measurement is done using a seating force gauge. Ordered 3 expander mandrels from K&M and use the one that allows me to have my bullet seating force to be 100% consistent at 10-15 lbs. Reguardless of your seating force target, this requires your brass neck thickness to be a consistent thickness +/- .0002. My necks are measured at 3 points and the outliers are culled.
Ben

 

[lawrence97]

And when they're not Roger will tell you that id depends on whose micrometer its used.

If you want a universal expander mandrel die with precision mandrel there is only one. It uses standard Vermont Gage pin gauges that can be bought for $3 on Amazon and they are precise within +/- 0.0002. If you want even more precision the mandrel cost $18 and have to be custom ordered from Vermont Gauge +/-0.000002 and you get a certificate of accuracy with the name of the guy that inspected and when. Not some lame excuse from Roger.


View attachment 1026752

Do the pin gages you are purchasing from amazon have the taper on one side as shown in your picture?

What does the die/collet cost?

Could you provide a link to exactly what you are purchasing from amazon?

Thanks.

 

[Ares]

But the K&M are just stainless and you have to lube where as the 21st century you can get coated in the tin and dont have to lube, correct? I was debating this same thing this morning



I too would like to know this, if every expander mandrel is .001 less than bullet diameter that would be perfect for .002 bullet tension after brass spring back, correct? (screw off guffey, no one cares to hear your diatribe on tension today)

If your worried about that PMA tool makes mandrels in carbide, and in custom diameters witch fits the 21st century expander die as that is the same die that PMA sells with they're own mandrels.

I would not run the TIN mandrels without any form of lube, at least use graphite or similar dry lube on em. Necking up new Lapua brass has over time started to wear on the TIN coating of mine, but they've also been used a lot.

 

[Dusty Stevens]

I thought using a bushing in a die got your correct neck tension not expanding it. When you expand your brass to turn as long as it fits the turning mandrel who cares? If you use a 21st century turner, use their expander. You dont need traceable tolerances to do this. When setting up neck tension that expander was long ago in the process and not even in the picture.

 

[spife7980]

All good info, I’ll reach out to Kenny porter for pricing.

Am I confusing the carbide and tin as far as no lube required goes? Or does that only apply in straight wall pistol brass and bottle necks always require it? Not that I would ever actually run unlubed brass through, that would require cleaning and then doing it, I would do it all before the final cleaning.

 

[Dusty Stevens]

And when they're not Roger will tell you that id depends on whose micrometer its used.

If you want a universal expander mandrel die with precision mandrel there is only one. It uses standard Vermont Gage pin gauges that can be bought for $3 on Amazon and they are precise within +/- 0.0002. If you want even more precision the mandrel cost $18 and have to be custom ordered from Vermont Gauge +/-0.000002 and you get a certificate of accuracy with the name of the guy that inspected and when. Not some lame excuse from Roger.


View attachment 1026752

So tell us who makes that one please

 

[Dusty Stevens]

http://www.portersprecisionproducts.com/porter/

thanks joe. how do you order just call him? i dont see much on his site.

 

[Dusty Stevens]

thanks joe