False shoulder on Wilson FL bushing dies for 300BLK and headspace issue

[st1650]

I'm kind of chasing my tail here so perhaps someone more knowledgeable than me can help.

I'm using IVI 300 BLK new brass. I bough a few Ks on sale last year, didn't have issue with the AR but now I have a new Defiance anTI with a match Bartlein barrel and it seems like I'm having issue with that brass headspace.

Here are the measures the shoulder using a Hornady headspace gauge:

New IVI: 3.075"
New RP 300BLK from factory Remington ammo: 3.055"
Seems like there's a pretty big difference right there which causes issue chambering (bit of force required to chamber the rounds) which means I'm using the bolt gun to bump the shoulder back which is probably pretty bad for the lugs.

So I resized a few pieces of brass using a Forster 300BLK FL die with expander ball to 3.065" and when fired they expanded to 3.072"

Now the goal is to have very consistent neck tension for long range subsonic, on my DTA 308W, I had great success, single digits ES/SD using Redding bushing dies for 308W and I'm trying to replicate this using 300BLK but I'm not convinced yet.
1) Redding does not make a 300BLK bushing die, so I went with a Wilson.
2) I set it up using the instructions but it seems to leave an unsized bulge by the neck as you can see on the pic here. Not sure if it's called a donut or a false shoulder but it just looks and feel wrong although it does feeds and eject perfectly fine

So here are my questions

1) I understand it's normal on say a 308 to have a bit of unsized portion at the neck (maybe like 1/16) but I'm not sure why it's so excessive on the 300blk casing, maybe due to the way the shoulder is ? Would it affect accuracy/neck tension? Am I overthinking it ? I tried setting the bushing with both the text facing up or down and same results.
2) Should I instead simply use the Forster die with a traditional expander ball?
3) If so, should I simply try to set it up to bump the shoulder back to 3.070 on all my new brass?

 

[Bullspotter]

For question #2 I would use the Forster die if it gives you the neck tension you want, I know the bushing dies will not always size the entire neck down, but yours seems to be pretty bad, would not be acceptable to me. Also looks like the (ring) is uneven from the end of the case, In the pic, the top where your red lines are, it looks further from the neck, then it dose on the bottom side.

For question #3, I would bump all the new brass back a bit if they are tight to chamber.

 

[Shootin Stuff]

It looks like your die is adjusted too far out.

Don't worry about the neck bulge at this stage, I think this is most likely a die setup problem and you need to take some measurements before thinking your die itself is bad.

What is the shoulder measurement of the sized IVI brass with your current die?

What is the shoulder measurement on the fired RP brass?

 

[padom]

Use the Forster FL sizing die. You aren't gaining anything with the bushing die over the Forster...I've sized and shot 10,000 or so 300Blk over the years with amazing accuracy.

This was all shot with LC brass sized with my Forster FL out of my 10.5" 300blk AR.

 

[st1650]

Thanks, I appreciate the help.

I'll go hit the range in 2 weeks with some 125 TMKs with new Forster FL resized brass. I'm not sure I can fully fireform using subsonic powder even with tinstar and 55K psi in quickload (I don't think QL properly simulates pressure of compressed trailboss and tinstar with heavy subs)

I did have great results with 18.6 H110 with TMKs with my AR couple of years ago.