Bullets getting jammed into seater die

[thedude824]

I typically use Redding type S bushing dies and Forster micrometer seating dies. When I started I bought all basic RCBS dies and quickly upgraded for calibers in which accuracy was a priority. I’ve never had an issue.
That being said I went to load some 300 black out subs using my RCBS dies. They hadn’t been used in a couple years so I spray them down with CLP inside and out to clean any residual gunk.
The cases were a combination of new Starline, once fire Starline from my gun, and once fired from friends rifles. They were all sized with the same RCBS sizing die. Case mouths were chamfered. Graphite lube was used. 3 of the 10 cases (no Starline) pushed the bullet into the die getting completely stuck. The case came out with a massively oversized neck that then wouldn’t hold a bullet. All cases were the same manufacturer. While I would like to blame the brass I’m not sure how the brass could be responsible. Bullets are 220 grain SMK seconds. I’m considering using this as a reason to finish my collection of Redding and Forster dies. Ideas?

 

[ma smith]

What are you doing for neck tension?

The case came out with a massively oversized neck that then wouldn’t hold a bullet. All cases were the same manufacturer. While I would like to blame the brass I’m not sure how the brass could be responsible.

Sounds like the bullet its acting like a -0.00 mandrel

 

[thedude824]

What are you doing for neck tension?



Sounds like the bullet its acting like a -.0.00 mandrel

I can’t control neck tension since it’s a basic sizing die. That thought crossed my mind as well. I just can’t figure out why there is tension when I place the bullet on top of the sized case. Then when I run it up into the die the bullet gets jammed into the die and the case comes down with a massive case mouth that no longer has any tension on the bullet. I don’t understand the mechanics, but it seems like a mandrel sizing die may be the solution.
I’m home now and may have misspoken. It looks like all 10 cases (including the 3 that did this) were Starline 300 blackout cases.
I guess I need to go take some case mouth measurements of the brass.

 

[Doom]

This description seems very strange but if the bullet is pushed into the neck and then the neck doesn't;t hold the bullet the neck is probably soft (maybe over annealed) with no springback.

 

[lash]

I guess I need to go take some case mouth measurements of the brass.

This. If you never took neck I.D. And bullet O.D. measurements and just assumed that you were good, then this can happen. Ideally, for bolt you want 0.002-0.003” press fit and at least that much for semi, though I prefer more.

In addition, you should disassemble the seating die and closely examine the interface of the seating stem to the bullet ogive. Not all seating stems work with all bullet profiles.

Especially when you are using the bullet as your sizing mandrel <sarc>.

Then, once you’ve done all that, try another and review your results. Make measurements and record them both before and after seating.