300BlkTalk

Hello all,

First post here on this forum. Hoping y’all could shed some light on this. I’ve been cutting down 556 brass and forming to 300 blackout by the most common method, harbor freight saw and jig, form/size in my Hornady die, and then trim to a length of approx 1.368. I’m having an issue where the mouth of the case is developing some deformation where it’s kinda getting this sort of shape: \/ That’s a little exaggerated, but it appears to develop a slight outward curvature at the case mouth after sizing. Any ideas to get this straightened out and what could be causing it? Anything helps, Folks!

Thanks,
Mike

My WAG is your initial cut leaves the case too long. So the case mouth is flared in the forming die. Or may be as simple as a die adjustment. My go to dies are RCBS and Lee. I have one set of Hornady dies that has ruined its last case with me (300 WSM) I could never get them to work for me.

My process is cut the brass down to a length that when formed gives me a case length of 1.365. With that "precision*" harbor freight saw....that means some cases need trimming and some don't. I measure and sort into bins and trim those with a beard and tumble them all in SS pins to smooth and shine. The less I trim the happier I am.

*when using the "precision" saw, make sure you are pulling the blade down straight as possible.....any side force in pulling makes for longer or shorter cases then set up for because there is a wobble factor...

It is the Hornady die causing the mouth deformation. The interesting thing is even when cutting it very close to 1.368 on harbor freight saw, the die still deforms the mouth. I’m thinking of sizing the 556 case before cutting it down in the harbor freight saw. Any thoughts on forming the 556 cases in the die before cutting them down to size?

Some brand dies are just not made for forming cases....resizing they do fine.....just not forming. I am not sure where Hornady fall in with that....as my only experience (resizing) did not fare well....

I have resized .223/556 cases before cutting off in a RCBS .223 SB die.....I tried that once in a 300BO die and had to deploy my stuck case removal kit!!
So I don't do that anymore .

My routine is to cut the cases at a length that when formed in the RCBS or Lee die comes out as close to 1.365 as possible. Did I mention I hate to trim.

My experience with forming in the HORNADY sizing has been positive. Once fired LC lubed, inside of neck as well, nicely formed case with zero drama. Out of about 50 cases, I had one needing a second pass, with no split necks. This was something that I just had to try. I now chop first, the longer neck cutoff would hang up in my chop saw setup. I use the same Hornady die set for all my BLK loads. I trim to 1.360 and have had great results.

When I form Blackout cases (using a Redding die) vs resizing after firing already formed cases, I found I had to have the sizing die in different positions for the 2 tasks. Specifically, when forming, my die has to make firm contact with the shell holder. When resizing, I have to have the die 1/2 turn out from touching the shell holder. I'm not saying you have to have the same amount of shell holder contact, I'm saying try adjusting your die in or out and see if it makes a difference when forming.

You can often get a flare in the neck if it is long or not supported by the die, that would depend on the internal shape of the die. It can also happen if the neck has not been chamfered and de-burred before forming. The more uniform and square the neck rim is the better it will turn out.

If it a particularly thick brass, it can make the problem worse.

Are you forming with the expander in the die? If not you might try with.

I form brass to fired length, then size it in a separate function.

@dellet. I actually had the expanded removed, but put it back in and noticed that the mouth didn’t have as much of a bell to it. I’m somewhat new to reloading. What would be the reason for this? I really thought the expander would be what creates a bell in the case mouth, which I why I took it out to begin with. My logic is off it seems....

I use a Lee die.

The factory lee die decapping pin was a little tight once they were formed and would occasionally give me problems with stuck cases and getting them apart. But I switched to a Squirrel Daddy expanding decapper now and all is well. They have 2 different styles.

Here's a few snapshots while in the process.

gomeybear wrote: ↑Sun May 12, 2019 5:09 pm @dellet. I actually had the expanded removed, but put it back in and noticed that the mouth didn’t have as much of a bell to it. I’m somewhat new to reloading. What would be the reason for this? I really thought the expander would be what creates a bell in the case mouth, which I why I took it out to begin with. My logic is off it seems....

The expander should be adjusted down close to the bottom of the die, this case is pretty short from the base to the bottom of the neck.

Think about the size of the bullet, and the neck size needed to have a press fit of the bullet. Bullet is .308”, neck inside needs to be say .305”. The sizing die will form the neck maybe as small as 300”, then as the expander comes back up through the neck, it stretches it back out to .305”.

That’s why you have less flare using the expander.

If you can post a photo it might be helpful. But a measurement of the largest part of the flare could also make it make sense.