7SAUM from 300SAUM

[medic727]

I just ordered 100 pcs. of 300SAUM brass to neck down to 7SAUM. Spoke to a Redding tech and he said all I need to do is run them through a regular 7SAUM FL sizing die, then use a 7mm expanding mandrel. I know I'll have to neck turn because the neck wall will get thicker. Should I also plan on having to ream the neck ID? I also plan on annealing as needed. This is my first attempt, a minor one, at case forming.

 

[dannyjbiggs]

Medic...just run them thru the FL die; and depending on your chamber neck diameter, you might be ready to go straight to loading? Only thing that I do not like about wildcatting the SAUM case to 7mm RSAUM is that the case neck is a little short for the RSAUM chamber, but it shoots okay.

In preparation to approach the FL die, I dab the case mouth lightly on my lube pad; then, load up a large cotton swab with Imperial Sizing Wax (or equivalent), and apply the wax around the front circumference of the case and just immediately behind start of the shoulder...don't get it on the shoulder, or you will get dimples.

Good luck,

Danny Biggs

 

[medic727]

Danny: thanks for the info. I,too, wouldn't normally be semi-wildcatting, but there's no 7SAUM brass to be found. I started out using Remington brass last year. Out of 200 pieces I had 16 with an improperly machined rim/extractor groove. That's before I did any other culling. So, I tried the Nosler 7SAUM brass. Expensive, but a great time saver. Also, it eliminates a whole bunch of variables. 6-7 firings, with annealing every reload cycle, still good to go. Couldn't find Nosler since late last season, so this year I figured I'd better get a hold of any 300SAUM I could find.

I've got a good benchmark to start with this season. Have a couple of new barrels I'm working up loads for. My 1-8" Shilen is shooting well under 1/2 MOA with my initial workup load at 64.5gr of RL-25 and 174gr SMK. Haven't fiddled with seating depth yet. So, after I get done with the 300 to 7mm transformation, I'll see how my handiwork performs.

 

[Kermit in Va.]

I was thinking that if you necked the 300 down to 7 it made the neck too short. Maybe I read it wrong but have you run into it being too short ?
Case OAL...

Kermit

 

[Cat MD]

As Danny pointed out they are a little short but it does not hurt anything you will need to trim them after a few firings. Herb