Friend gave me 100 rds new 375 Win brass and RCBS 375 to 357 Herret form/trim die. Experience with these, anyone? Do I size first in the form/trim die leaving the shoulder long, trim and then size in 357 full length die to move shoulder back to match my barrel? Never had a trim die before. Top is hardened so I can file off the top, right? Thoughts...tricks?
Cheers,
Dave

That's expensive brass to form the Herretts from. I always formed my 30 and 357 from 30-30 brass. I ran the 30-30 case into my trim die and used a very fine tooth hacksaw to remove the excess and then trimmed in a Forster to final length. The trimmer was faster than the file and trim die, but the trim die will definitely work. After forming you want the fit to be snug. Keep moving the shoulder back in very small increments until you get the action to close with a hard snap motion. Good luck and have some fun.

Rupe,
I've always used 30/30 brass, too. I read(somewhere?) that the 375 brass can be substituted and is "stronger" brass?
Cheers,
Dave

The last two batches of 357 Herrett brass that I made were from 375 Winchester. It is indeed supposed to be a stronger brass and therefore should last longer. Depending upon how tight your chamber is, you may end up having to turn the necks when using 375 brass. I haven't had that problem, but it can happen. I compared some of my 375 based 357 Herrett cases to some that I had made from 30-30 brass, and found that the case capacity was a little less in the 375 based cases. I do not remember the exact difference at this point and it may not be significant, but there is indeed a difference. Point is that your pressures may go up a little bit faster, so approach maximum loads carefully. I, however, haven't had a problem with any published maximum loads that I have tried in my 375 based brass.

Your plan of attack on forming sounds much like what I do. The other replies above hit the mail on the head regarding the final shoulder location. Have the gun there at the loading bench and just keep turing the die in until the action will just close on the case. I tend to go just a hair further on the die after the gun will just snap closed - maybe a 1/16 of turn at most.

Caution must be taken when working up loads for the Herrett's when formed from .375 Winny. The Winny cases is stronger because it is thicker. A thicker case means less space for powder and in turn, less space for gas expansion when the powder is ignited. If you choose to use the cases he's given you, be sure to start with the lowest loads listed and work up carefully.

i havent formed any myself, but from what i was told you can also run the cases right into the 357 herrett sizer dies abd form them that way. i may be incorrect though, these guys sound like they know a whole lot more about it than i do.

What Dan said - but it is the stuff you should use. You'll not lose any because you're sizing down, not up, and it last longer because it is stronger. It's all I use in mine.

Doc,

I took Dan's advise and was cautious when using 375 Win brass for the 357 Herrett, but now, that's all I use. I prefer necking down than necking up, I ruined too many cases.

The advise of caution made me conduct a test of various 357 Herrett parent cases. I choose to use Rem 30-30, Win 30-30, Rem 32 Win Spl, Win 38-55 and Win 375 (10 each). After forming and trimming to size. Here's how they stacked up against each other:


Rem 30-30
Win 30-30
Rem 32 sp
Win 38-55
Win 375

Doc,

I took Dan B's advise and was cautious when using 375 Win brass for the 357 Herrett, but now, that's all I use. I prefer necking down than necking up, I ruined too many cases while necking up.

The advise of caution made me conduct a test of various 357 Herrett parent cases. I choose to use Rem 30-30, Win 30-30, Rem 32 Win Spl, Win 38-55 and Win 375 (10 each). After forming and trimming to size. Here's how they stacked up against each other:


Rem 30-30 123.6 grs. (.0094 neck)
Win 30-30 129.9 grs. (.0098 neck)
Rem 32 sp 123.3 grs. (.0075 neck)
Win 38-55 130.6 grs. (.0097 neck)
Win 375 141.0 grs. (.0100 neck)

I believe the potential danger comes not only from the reduced case capacity but also from the increased neck tension. If care is taken, however, I do believe you get better case life. What usually happens to me is, I'll get lazy and stop checking my sizing process, push the shoulder back a touch, and the cases will stretch and separate. I guess my point is don't loose focus on proven techiques and any brass should be fine for the 357 Herrett.