300BlkTalk

I just recently started loading for the Blackout. My first subsonic loads used H110 and the Hornady ELD-Match bullet. These were chronographed at 1025fps. Perfect function and good groups.
I then tried loading 50 of these bullets using 17.3gr of AA-1680 to obtain a Supersonic load. This load is a compressed load that slightly deforms the area below the ballistic tip of each bullet. Overall length is 2.255”.
I use RCBS dies, so wondered if I need a different seating stem to contact the bullet further below the ogive, and keep the bullet from deforming?
The loaded bullets have a light wave in the metal, below the ballistic tip. None of my manuals indicate that this is a compressed load, but it is. I used virgin Starline brass.
Any suggestions will be appreciated.
Thanks!

First suggestion is back of the load.

Most manufacturers will offer a VLD seating stem, that may help. Hornady came out with new stem when the ELD line was intro diced.

I’m guessing none of your load books listed Starline brass in the data either. It will make a difference.

Probably safe to say, most books do not accurately flag compressed loads. You’re best to figure that you are on your own for that. Use a fired case that a bullet will slip into the neck easily, drop the powder charge, slip the bullet in to rest on the powder, and measure COL. That will give you a base line where compression starts.

A fine ball powder like 1680, dropped correctly, will not compress much. It’s just too dense. .010”-.015” is about it. After that what you found holds true, bullets start deforming and it’s harder to keep the bullets straight, or without a stout crimp, the powder pushes the bullets back out.

Add to that, Starline has one of the smallest case capacities of all the properly headstamped brass. It’s going to be difficult to get any published max load without running into trouble.

Thanks for the insight!
I figured I would change to a different powder, but didn’t know about the Starline brass capacity issue, nor the Hornady VLD Seating stem. Your info is very helpful.