Rechamber 7x57r to 7x65r

45calmuzzleloader

Is it possible to rechamber a 7x57r to 7x65r? I understand the 7x65r operates at higher pressure. Reason I ask is my 1962 vintage JP Sauer drilling 12 ga. X 7x57r chamber has neck erosion problems. Previous owner must have routinely fired cartridges with split necks or brittle brass that split on firing, causing the neck of the chamber to become damaged. I'm able to prevent my cases from splitting by annealing the case mouth every other loading. I would only fire reduced pressure loads if rechambering is possible. Thanks in advance.

rufe-snow

From the data, in Cartridges of the World. Given the dimensions of the 2 different cartridges. It seems to be a substantial difference between the 2.  The 7 X 57R, is just the standard 7 X 57 with a rim. Whereas the Brenneke cartridge, has a smaller neck diameter by .015 and longer by .020.  It would be iffy to me, if the 7 X 57R's chamber, would be able to be altered safely. To work with the Brenneke cartridge. 

My call would be to keep on annealing the brass. Rather than risk, screwing up the 7 X 57R barrel.

charliemeyer007

Have you used some sort of bore scope to inspect the chamber. What does the chamber cast reveal?  There are some china laptop fiber optic camera units for like $20.  Perhaps you could electroplate some metal in the pits.
When I stationed in Germany, I almost bought a JP drilling. 16x16 and 22 Savage Hipower.  

45calmuzzleloader

I haven't looked at the chamber with a scope or made a chamber cast. I'm just going by fired brass inspection. The necks of unfired cartridges measure .314" o.d. Fired cartridge necks measure .327". But where the neck and shoulder meet on a fired case it measures .320". I guess the brass is going to contract a couple thousands after filling the chamber. Cases extract easily. The bore is pretty rough but it shoots fantastic, 3 shot 1" group at 100 yards with 175 grain round nose soft points and 38 grains of Hybrid 100v powder around 2200 fps. I'll just keep annealing and keep pressures low.

charliemeyer007

That is good shooting, rough bore or not.  It sounds to me like the chamber was cut big, maybe by design for extraction.  The old 7mm in rolling blocks all had large chambers in my experience.  I think you have a good solution. 
I wonder if you could get thicker necks by necking down 8x57R cases or did they make 9.3x57R.  You would still be working the brass hard with standard dies, maybe modify a neck sizing die only like from a Lyman 310.