Neck tension question with bushing die

[absolutchris]

I know that you just measure the OD neck of a loaded round. What do you do if you have unloaded brass (ie: ordered a new box of Lapua)? Can you just seat a bullet into a sized case at any depth and just measure that to select your bushing? Or does that measurement change with bullet seating depth?

Thanks in advance

 

[Supersubes]

I know that you just measure the OD neck of a loaded round. What do you do if you have unloaded brass (ie: ordered a new box of Lapua)? Can you just seat a bullet into a sized case at any depth and just measure that to select your bushing? Or does that measurement change with bullet seating depth?

Thanks in advance

Many bullets are slightly fatter at the bottom their bearing surface, near the boat tail. Usually one or two ten thousandths. Not a big deal. Probably goes without saying, but just make sure you’re measuring in a location where there’s bullet underneath.

 

[Lynn Jr]

Seat a bullet into your new brass and measure it then subtract 0.003 and your all set.

 

[bunsen27]

As long as the bearing suface of the bullet is seated in the neck of the cartridge case, and you take the outside case diameter measurement from that point, you will be good to go.

@absolutchris how far down the rabbit hole would you like to go on this subject? It's really quite interesting.

The bushing die is actually just the first step to setting neck tension. Although you can use the expander ball, you probably should also be using a mandrel die to set the final neck tension.

http://www.snipershide.com/shooting/threads/bushing-size-for-223-lapua-brass.6919586/

http://www.snipershide.com/shooting/threads/expander-mandrel.6917570/#post-7411669

http://www.snipershide.com/shooting...-mandrel-in-the-process.6913984/#post-7371322

@spife7980 can definitely explain choosing the proper busing and mandrel much better than I can.

 

[canezach]

I do what @bunsen27 mentioned. I size with a bushing that is 0.002" under the loaded neck OD and run a mandrel through the neck to ensure the interior of the neck is perfectly round and my neck tension is set. The two mandrels are expander and neck turning. The expander is 0.001" (around 0.0015" after some springback) and the neck turner is 0.002" (again, maybe 0.0025"). I've found most of my loads prefer the expander mandrel neck tension, but it's a very minor difference in ES and SD between the two.

 

[bunsen27]

I do what @bunsen27 mentioned. I size with a bushing that is 0.002" under the loaded neck OD and run a mandrel through the neck to ensure the interior of the neck is perfectly round and my neck tension is set. The two mandrels are expander and neck turning. The expander is 0.001" (around 0.0015" after some springback) and the neck turner is 0.002" (again, maybe 0.0025"). I've found most of my loads prefer the expander mandrel neck tension, but it's a very minor difference in ES and SD between the two.

Yep, the limited testing I've done has also shown a preference for the expander versus the turning mandrel.

Where I have seen the biggest SD/ES reductions has been with virgin brass. Whether it be Lapua or LC, all have benefited from sizing then running a expander mandrel through the case neck.

Reading several of the threads on here about the subject have been extremely enlightening!

 

[absolutchris]

Thanks guys. Def not wanting to go down the rabbit hole too far, at least yet, I'm just getting set up and started

Thanks for the info!!

 

[Sutherlandsd]

The sinclair expanding mandrel is not that far down the rabbit hole... It's really something you should be doing and its cheap... I think Brownells has it on sell for less than $30, go ahead and buy the expander mandrel you will rarely use the neck turning (at least I dont think I ever have.). You can also use that one die for most all of your calibers under .35 so go ahead and buy the other mandrels to save the shipping.

 

[spife7980]

To address that^

I use the turning arbor to set my neck tension. The "expander mandrel" is .001 under bullet diameter, the "turning arbor" is .002 under bullet diameter. I like the .002 under.

 

[Sutherlandsd]

It's def best to buy both the turning and the expander when purchasing since most places will rape you for shipping on such a tiny part.