8X58RD Oversize Chamber

[gunboat57]

My Swedish RB sporter was the first gun that I began reloading for years ago. I bought RCBS reloading dies and an extra expander so I could seat 200 gr .329 cast boolits to fit my .329 groove diameter barrel.
With light charges, like 12 gr Unique, the shoulder barely moves forward on firing. But with heavier loads the cartridge fireforms completely to the chamber. Here is a pic showing a fireformed case on the left and a freshly FL sized 45-70 case on the right. Does it look like my chamber is excessively oversized or is mine typical?
I anneal the neck and shoulders after each firing now and only neck resize.

[skeettx]

Well it certainly does expand to fit your current chamber
But since you neck size, your brass should have a good life.
No safety issue here, head space is on the rim
Mike

p.s. when making brass from 45-70, can you not screw the sizing die all the way down and have
the case chamber?

[gunboat57]

Skeettx, that's a good suggestion about backing off the FL sizing die when forming from 45-70 brass. That might cut down on working the shoulder area. But it seems like the shoulder of the chamber is in the right place but the taper from shoulder to neck is longer than in the FL sizing die. I have more 45-70 brass to form so I might give it a try anyway.

By the way, I'm not sure how other folks trim the rim diameter down when making 8x58RD from 45-70, but I put the formed brass on a 1/16" drift punch held in a vise. The 1/16" part sticks through the primer hole and the case mouth is able to turn on the body of the punch. Then I use a file on the rim. I stroke the file at an angle to the rod so that the case spins a little as I file. I end up with perfectly round rims of the proper diameter.

[leadman]

I also have the identical rifle. I do not see a problem with your case. The neck is as normal for a reformed 45-70 that ends up with a short neck.

[gunboat57]

I guess they made the chambers a little "generous" to make sure cartridges could be seated. Maybe for the same reason .303 Brit chambers are usually deep. I only neck size my .303s, too.

[leadman]

With the light loads of Unique I use behind the Lyman 160gr Loverin RN the case will not form the shoulder completely. I do have a load with 4759 behind the Lee Karabiner 235gr boolit that does form the shoulder completely. This is probably what is happening to your case also.

[enfield]

I use 8x56 Hungarian and it bulges similar, it measures .493 in front of the rim and about .502 a 1/4 inch ahead of that. but I see a 45-70 case measures about .500 for quite a ways up the case. I also shoot about 12 gr unique and about 17 - 19 gr 4759.

[gunboat57]

I've found that 20 grs SR4759 pushing a .329 150 gr jacketed thingy will expand the shoulder but the neck doesn't expand 100% of the time. I might bump up that load a little.
Just to be consistant, I am fire forming all my brass using Bullseye and coffee grounds. Usually folks use cream of wheat but I don't have cream of wheat and I do have coffee. Good to the last hammer drop.

[17nut]

Midsouth has a Lee mould for the 8mm Mauser:
Attachment 169512
http://www.midsouthshooterssupply.co...roduction-Mold

Works a treat!


As cast the bullet runs @.325-.326" and i lube the bottom 3 grooves.



I push them to @1850fps and it shoots like a laser past 150yards.

[leadman]

Use caution when loading for these old RBs. If the breech gives way the parts usually end up in the shooters eye! This has happened.
I hold mine down to around 1,450 fps with the Lee Karabiner of 235grs.
There is data out there that is intended for the Danish Krag that is too hot for the RB.