Can I use a standard .338LM neck bushing die on a .338 Improved?

[MadCowRacer]

I have some custom dies on backorder/backlog but the date of my hunt is creeping up faster than the dies will be done.

Can I measure my fire forming loads neck diameter for the bushing size, and use a standard neck bushing die to build my load ladders?

As standard 338LM cartridge measures .5825 at the rim of the case, and tapers to .5475 at the shoulder.

My fire formed brass measures .5835 at the rim of the case, maxes out at .5840 about 3/8" forward of that and .5700 at the shoulder.

My standard FL .338LM dies will not work to decap even with the pin adjustment about 1/2" out of the bottom of the die.

Does anyone have a Redding bushing die that they could measure? Or am I barking up the wrong tree completely. I haven't done any neck sizing, or bushing sizing yet, I've been full length sizing with minimum should bump, so I'm not sure if this is even possible.

Here is the brass before and after fire forming

 

[Pdvdh]

Quick answer = no.

The enlarged shoulder diameter of your fireformed cases will contact a standard 338 Lapua neck bushing die before it's inserted far enough to seat a bullet.

I wouldn't buy a standard die. If you could borrow one, you could try - but I think it's a no-go.