Troubleshooting- Forming 7mm RM from 300 WM brass

[375RUGER]

Objective: To form 7mm RM brass for minimum chamber neck clearance
Tools I have on hand:
7mm RM full length die
300 WM neck size die
7mm RM trim die
Annealing equipment
Redding case trimmer
Outside neck turner
Imperial sizing die wax
Knowns:
7mm RM FL die will size the neck to .306” OD
7mm RM Trim die will size the neck to .316-.3165”
300WM case is .120” longer than 7mm RM case
My chamber measures .3172”


I’ve never formed brass before and beseech those more knowledgeable for input and opinions.
What I have done so far.
1. Trim brass to 2.507”
2. Anneal neck and shoulder
3. Resize in 7mm RM trim die
This is the result: (300WM case shown for comparison)

I believe from this first try that I can get the neck OD to within .001” diameter clearance of the chamber neck and have enough neck to seat a .285" boolit.
The dents in the case body below the shoulder are from too much lube. This I know how to fix.
.
How do I get rid of the shoulder crimp?
.
Should I cut some off the bottom of the 300 WM die so that I can run the brass a bit further in and get the shoulder set back a bit before I move to the 7mm die?
.
If so, How much should I try to set the shoulder back?
.
Would I need to fire form this crimp out of the shoulder?
.
Your help is greatly appreciated.

[btroj]

Try annealing after the forming.

Often times using the 7 mm seating die with the guts removed will let you from the case with a larger neck diameter that is then cleaned up by resizing in th FL size die.

I also prefer to cut to length after reforming.

Oh, it is far easier with new cases. Fired cases often are just enough harder to be a pain to reform. Annealed cases are often too soft, new seems just right.

[GRUMPA]

^^^^^ What he said, when I convert cases I rarely anneal first. Well that and I use my swage lube of Anhydrous Lanolin and Vaseline 50/50 and put it on the body only and nowhere close to the neck shoulder area..

[oneokie]

Check the trim die to see if it has a vent hole in the shoulder area, and if it has the vent hole, make sure it is open. The vent does get plugged with lube at times. BTDT

[Hardcast416taylor]

I can only ask "why try to make the case with so much of it already around"? Yes, I understand the need to want to make your own - but is the headache worth it?Robert

[375RUGER]

^^^^^ What he said, when I convert cases I rarely anneal first. Well that and I use my swage lube of Anhydrous Lanolin and Vaseline 50/50 and put it on the body only and nowhere close to the neck shoulder area..

I'll reduce the lube then.

Check the trim die to see if it has a vent hole in the shoulder area, and if it has the vent hole, make sure it is open. The vent does get plugged with lube at times. BTDT

No vent. I'll do like Grumpa says and see how it works. And maybe switch to the seating die also.

I can only ask "why try to make the case with so much of it already around"? Yes, I understand the need to want to make your own - but is the headache worth it?Robert

I have plenty of 7 RM brass. I happen to have a good amount(120) of 300WM and want to try and make brass that fills the chamber neck better.

[375RUGER]

Keeping the lube off of the shoulder cured it. I'm going to make 5 and open a sizer up .0005" and see if it's worth pursuing further.
Seating die necks it down too far. The trim die still give me better neck diameter.

[375RUGER]

This project is over. After firing there is not enough neck thickness to fit the factory chamber and have enough tension on the boolit, definately not enough with condoms. It might be OK with .287 boolits, but not in my chamber.
I'll do this again if I get some 375 H&H or 338WM brass.

[geargnasher]

You'd be better off starting with the parent case, much less neck/shoulder crease to have to iron out on the new neck. Don't count on them being thick enough to fill your neck even then though, try one and see first. I'd do it for you if I had a 7mm WM sizer die. If you like, I can send you a few .375 cases that I found at the range the other day.

Gear

[375RUGER]

I'd appreciate that.
Something to do with some down time, and I had these 300WM cases.....and I've wanted to make brass to fit this rifle for a long time.