7mm PRC Project/Including making brass from 300 PRC

[Rune479]

I am putting together an NRL/general hunting gun in 7PRC. For the remainder of this post (7) will refer to 7mm PRC and (300) will refer to 300 PRC as the discussion will pertain to brass and the modification thereof.

Time is not on my side and component availability make manufacturing and attaining the necessary materials difficult.

Scope:

I need to manufacture brass for the 7 using the 300 on hand. Starting with virgin Lapua cases. If you want to know why, search for anything 7PRC related (other than rifles). 500 available to play with. ER...UM.... develop a load with. Well, at least that is how many I started with.

Time frame is tight, I am prepping for the next NRL match.

The rig:

Lone Peak Ti Fusion
Carbon Proof in 7PRC
ASR Flash hider
HNT26 Folder Arca
ZCO 5-27

I have a relatively well-equipped room, with all of the usual suspects.
AMP
Zero
LE Wilson
Sinclair
RCBS
Redding
and yes, the old standby LEE.


Current procedure basics:

Amp Two annealing passes #65 bushing, 0180 as setting

Run through the Redding FL sizer .200 standoff using feeler gauge. Stim removed.

Trim on the Wilson/Sinclair removing half the neck

anneal 0251

Redding FL sizer .100 standoff using feeler gauge. Stim removed.

anneal 0251

Trim close to final length (+0.015)

Final FL size with plenty of preload on the die. Stim removed.

Final prep including expander die and inside neck reaming. Necks stay .017 to .019 thick.


AMP settings attained using Aztec.

I am still trying to source a 7 mandrel for the NT-4000. Fingers crossed. I think outside neck reaming will get me pretty close. I usually look for approx. .014 thickness, or whatever gets me concentricity without unnecessarily thinning the necks.

Currently the procedure goes well through the second trip in the sizing die.

On the third trip the brass will ripple very slightly in the body below the shoulder. I was getting rippling above the shoulder on previous attempts, this seems to have largely dissipated by adding the extra steps.


Chambering is not possible as yet. It is very close, in the ballpark of a very hot load on a very hot day.


I do not want to get into minutia of datum lines and the like at the moment. I have more tools on the way. Let's assume, for the moment, that the barreled action is "in spec".

My initial question pertains to gross procedure. What have you done that works? What can I add or remove to get more consistent results? Anything that will get me to a final result that is incumbent to the precision and success of the project.

Keep in mind, we are pushing the brass down from .308 to .284 and bringing the shoulder back around .300".


I promise pictures and maybe a witticism or two along the way, in addition to load development data and results.

 

[Ringostar]

Talk to @Uthink Uknow on this forum. He has a wildcat die available, that would help you a lot. Instead of trying to push the entire shoulder back at the same time, it’s done in steps. I’m not sure what their actual steps would be. But picture all of the cartridges based off of the 308, 338 Federal, 308, and 7-08. Now if you’d run a 30-06 case into a 338 Fed die, it would push the outer part of shoulder back because of the bigger neck. Then run the case into a 308 die, and push a little more of the shoulder back. Then into a 7-08 die and it would squeeze the neck down, plus the rest of the shoulder. This would be an option for you, without creating the wrinkles and all done with one die.