Help on 300 blackout fireforming load

[CENTEX BILL]

I have a number of 300 blackout (300 Whisper) cases formed from 223 and not yet fired. I have some left over 30 cal 125 carbine bullets from a previous trade. I would like to use the plain based bullets for a mild fire forming load for these cases to my chamber. I noticed the shoulders on the case are much sharper on the cases after the initial firing. (I used the David Tubb Final finish kit to break in the new stainless barrel on the rebarreled Rem 700.)

I have Unique, Red Dot, 2400 and Trail Boss powders. I would like a load with an approx 1200 fps velocity.

Anybody have any suggestions for a mild load.

Thanks,

Bill

[nhrifle]

Congrats on the rifle build and excellent caliber choice! I havn't worked with any loads as low as you like to go yet, but if I had to guess, Trail Boss would be a good one to start with say 7 or so grains and go from there.

Not sure why you want to fireform the cases. I have formed and loaded a couple thousand cases in mine so far, and accuracy and performance are excellent with newly formed brass.

[Gunnut 45/454]

Is this for a bolt gun? Cause if your shooting them in a AR your going to full length size anyway! As you should. So then there be no need to fire form!

[felix]

Correct! Shoot full tilt always, new or old brass. Load is too hot when brass gains in length. Check after every firing until load is finalized. Don't forget, because this is a SMALL case for the application. ... felix

[nhrifle]

I havn't noticed any real growth in the brass, even with hot loads. Maybe it's because I have been forming mine from military cases and the brass is tougher. My indications of high loads are read in the fired primers.

[felix]

Great!

[Jailer]

You'll know when you are too hot. :twisted:

http://i19.photobucket.com/albums/b180/Jailer/presssure.jpg

[scb]

You'll know when you are too hot. :twisted:

http://i19.photobucket.com/albums/b180/Jailer/presssure.jpg

You can get the exact same thing to happen by using 223 formed brass in some Whisper chambers with mild loads. Be sure to check you neck wall thickness.

[Gunnut 45/454]

Jailer
I found using H110/W296 will get you there fast. I wore out quite a few cases that way. Now I stick with IMR 4227 and Lil'Gun. The AAC pink tip brass really sucked. Got one reload and they were toast!

[Jailer]

That flattened case head was from H110. Boy once you approach max it doesn't take much to step way over.

I'm working with Lilgun now and it seems to be going well so far.