Making 300 Blackout having issues........

[Slapps74]

So I'm having some issues and hoping someone can help. I am using a Dillon 650 and a RT1500 trim motor. My new Dillon trim die for 300 blackout sizes the neck internally to .295. My Dillon size die will resize the neck to .306. The problem is when I resize the neck and try to finish trim, the trim die takes the neck back to .295. If I size the neck again it messes up my case OAL. Maybe my process is messed up.

I trim 223 in the same way and have no issues. I use my Dillon sizing die in station one and my trim die in station three on a Dillon short trim tool head.

The process is as follows starting with 223 brass;
1. Decap
2. Stainless media clean & Dry
3. Lube
4.Swage, form & rough trim to about 1.375
5. Neck size with Dillon size die and final trim to 1.358 +/- <------ where my problem starts WTF

Not sure if I got a bad trim die from Dillon or what or if I need to just need to trim to the length I want then size the neck and load. Going to call Dillon tomorrow and see what they say.

[Irving]

Interested for info as well as I'm about to pick up this caliber and have tons of questions.

[Jamnanc]

I would use a universal deprime instead of your size die in station one. Make sure you keep the cutter close to the trim die so there isn't a lot of clearance and trim to length. Why are you doing it twice? Use an expander ball to open it back up. If I don't open back up it usually sits at 3.03 I think your blades are too far from the trim die.

eta: If you eliminate the neck die and use a Lyman m behind the final trim, I think you'll be happy with the results.

[Hoser]

Tumble clean in corn cob. Universal recap die first. Trim to 1.355.

Then tumble in stainless media.

Load as normal.

[Slapps74]

So it doesn't sound like you guys do a rough trim then.

[Jamnanc]

No, that's why you bought such an expensive trimmer. It does the resize so the neck die is unnecessary. Your working the brass to death, if you want the neck opened up, just run an expander or m die in the final station.

[Slapps74]

Ok cool. I will give that a try. Still going to talk to Dillon and get their thoughts as well. Does anyone stock the Lyman M die that you know of?

[Slapps74]

Thanks by the way.

[Slapps74]

So according to Dillon they said to chamfer the neck and press the bullet in. If the neck measures .295 and the bullet measures .3075 that would be .0125 neck tension which seems like a lot to me. I think I will try Jamnanc and Hoser's process.

[Jamnanc]

I got my m die from midway. Your neck die adjusted so only the expander ball touches will work in the mean time.

[Slapps74]

Thanks again for the info. I will try some things tonight. Any favorite load for supersonic. Have some 125gn SST's and 4 pounds of 1680.