8 mm to 257AI

[Duckiller]

Need advice. World does not want to sell me 257 Roberts brass. I have a small supply of 8 mm Mauser brass. No 8mm guns nor do I want one. After lubeing with an RCBS lube pad I ran three pieces through a 7mm resizing di. Lots of dents in the shoulders. Ran one case through a 257 di. No more dents just what the 7mm di put in it. I can probably eliminate the dents when I blow the shoulder out,m but I would prefer not to have the dents to begin with. Brass is R-P that i got at a gun show several years ago and is at least once fired but shiney. I have several dies that I could use to resize the neck before I go to the 7 mm. 30-32 are available. I would welcome any and all suggestions to prevent the shoulder dents.

[WehrmannsGeweher]

Expensive, but fully prepped. It's all I use for my serious accurate rifles.

https://www.midwayusa.com/product/81...r-custom-brass

[jblee10]

I use Imperial Case Forming Wax. Use a minimal amount rubbed on the neck and body with the fingers. The dents you are getting are probably from an excess amount of lube. Imperial Wax is amazing under high pressure. 8mm to 257 is the long way to get there. 257 Roberts was originally formed from 7 x 57 brass I believe. You will need to watch the neck thickness after forming. I'm not a fan of having to neck turn or ream.

[cwtebay]

Need advice. World does not want to sell me 257 Roberts brass. I have a small supply of 8 mm Mauser brass. No 8mm guns nor do I want one. After lubeing with an RCBS lube pad I ran three pieces through a 7mm resizing di. Lots of dents in the shoulders. Ran one case through a 257 di. No more dents just what the 7mm di put in it. I can probably eliminate the dents when I blow the shoulder out,m but I would prefer not to have the dents to begin with. Brass is R-P that i got at a gun show several years ago and is at least once fired but shiney. I have several dies that I could use to resize the neck before I go to the 7 mm. 30-32 are available. I would welcome any and all suggestions to prevent the shoulder dents.

Did you anneal first? There is a YouTube videographer "Ammosmith Reloading" that had a great series on the subject. I struggled making 250-3000 brass without dents, and now seem to be able to pull it off without too much problem. Cheers

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[stubshaft]

I anneal the necks of 7mm brass and use Imperial Sizing wax sparingly to form my 237 AI cases.

[cwtebay]

Need advice. World does not want to sell me 257 Roberts brass. I have a small supply of 8 mm Mauser brass. No 8mm guns nor do I want one. After lubeing with an RCBS lube pad I ran three pieces through a 7mm resizing di. Lots of dents in the shoulders. Ran one case through a 257 di. No more dents just what the 7mm di put in it. I can probably eliminate the dents when I blow the shoulder out,m but I would prefer not to have the dents to begin with. Brass is R-P that i got at a gun show several years ago and is at least once fired but shiney. I have several dies that I could use to resize the neck before I go to the 7 mm. 30-32 are available. I would welcome any and all suggestions to prevent the shoulder dents.

Apologies - meant to put in that I would suggest using your 30 caliber dies first. Squeezing from 32 to 28 is a bit of a stretch. I usually try to bump in and out of the die several times before full insertion into the die. Repeat with the 7mm die. My problem was too much lube. My biggest jump down is 50-110 to 348 Winchester. It takes me 3 dies to get there.

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[Duckiller]

Made some cases today.
As cwtebay suggested I used a 30 caliber die before 7mm. I used a 308 Win RCBS neck sizing die to start. Then a Redding 7mm neck sizing die. finished up with a RCBS FL sizing di. Imperial sizing wax was not available so I bought a can of Hornady one shot spray lube. $10.00,m been a while since I have bought this . Made a guess on how much to set the shoulder back. 308 di work good for this. Had minimual lube dents. Of the 25 cases I tried to chamber 23 worked fine. one case didn't get put through the 257 di. 7mm cases don't fit in 25 caliber guns. One 257 case was difficult to close the bolt on. Will fix both cases tomorrow. Also have to dig out a 25 caliber mold for boolits to fire form the cases. I appreciate the suggestion of Nosler brass but at age 76 I am too cheap to spend that much for ammo let alone brass. Which ever son/daughter gets this gun can figure out how to make ammo for it.

[cwtebay]

Made some cases today.
As cwtebay suggested I used a 30 caliber die before 7mm. I used a 308 Win RCBS neck sizing die to start. Then a Redding 7mm neck sizing die. finished up with a RCBS FL sizing di. Imperial sizing wax was not available so I bought a can of Hornady one shot spray lube. $10.00,m been a while since I have bought this . Made a guess on how much to set the shoulder back. 308 di work good for this. Had minimual lube dents. Of the 25 cases I tried to chamber 23 worked fine. one case didn't get put through the 257 di. 7mm cases don't fit in 25 caliber guns. One 257 case was difficult to close the bolt on. Will fix both cases tomorrow. Also have to dig out a 25 caliber mold for boolits to fire form the cases. I appreciate the suggestion of Nosler brass but at age 76 I am too cheap to spend that much for ammo let alone brass. Which ever son/daughter gets this gun can figure out how to make ammo for it.

Well done!!! There are many different opinions on fireforming cases. I like the cream of wheat method. A light load of pistol or shotgun powder, a little wadding, case full of cream of wheat, a touch more wadding and fire. I have been discouraged from this, but really like my actual loads to be ready for anything at the word go.

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[Wayne Smith]

I would size from 8mm to .30 to 270 or 7mm to .25. Then anneal. You don't want to anneal the shoulder prior to sizing down. This will cause shoulder collapse, I've had it happen making 25 Krag. When I make 25 Krag AI I size to 7mm and to .25. You do want the shoulder annealed when you fireform or you may get shoulder splits. When making 25 Krag I lost almost 50% of the cases to shoulder splits before I annealed.

I also took out the decap/expander from my dies. I did not want to stretch the annealed cases. I use the Lyman M die to expand even for condom boolits.

Once you have your brass made neck size only.

[Hardcast416taylor]

I just stumbled across 81 fired .257 Roberts cases in my loading room that I would part with for $50 + SFRB shipping. PM me if interested.Robert