In a bolt gun, would you run .001 neck tension? .2830 mandrel on a .2840 bullet to be specific. I’m a little worried about this not being enough and was planning on a .2825 mandrel but I have no idea when they will be back in stock. .2820 is also sold out and 2815 is too small to effect most pieces of brass after coming out of the neck/shoulder bushing.

.001" is very light. But it depends on what you are doing with the ammo. If it's for a hunting rifle, no, I wouldn't run .001". If it's for ammo that sits in an ammo box and will be used for a target rifle on a bench, and the ammo won't be moved around or used in the field, then that might be ok. But when you run .001" tension, you will get some brass pieces that is less and some more. You risk moving the bullet in the case. I try to use .003"-.004" as minimum. I would think the .281" would be ideal.

I run things anywhere between .002" and .004"

That .2815" would work just fine.

That’s what I was afraid of. My neck bushing is only .002 smaller than my loaded ammo now, so I don’t know if I would benefit from a smaller mandrel.

Went to order the .2815”. Now the 5/16 ER11 collet that holds it is out of stock. it wasn’t yesterday.

This 100% on me. I was going to order a couple of weeks ago but saw they would be having a Black Friday sale. Sale came around Friday and it was only $5 off. By the time I grabbed my wallet what I wanted was gone. Now I’ve decided and the collets gone.

To follow up. I ordered the .2815” and was able to find the ER-11 5/16 collet on eBay ($18 shipped instead of $50 plus tax and shipping in case anyone needs one).

It looks like with Lapua brass, .308 bushing, and .2815 mandrel you get .3080” sized, and .3105” with the bullet seated. That makes .0025” neck tension, at least on my test pieces.






It’s worth noting that the .308 bushing was actual net of .306” not sure why that is. If anything I would have expected larger from spring back, but these were freshly annealed.

It’s also worth saying , the modular SAC die is the easy button. I was able to change the decapping rod for the mandrel without having to reset my die. So it sizes with a shoulder bump, bushing sizes the neck, then mandrel sizes the neck. All in one stroke.