looks like a setback and rechamber .. not feeling on top of my game .. little under the weather .. so, can you rechamber a 7x57 to 7x64 or 280? require setback or a new barrel? assuming milsurp 98 in 7x57

The 7x57 (if milsurp) will have a bore and groove diameter of 6.96mm/7.24mm which is the same as the 7x64. A 280 has a bore/groove of 7.04mm/7.21mm and the freebore diameter and chamber neck diameter will not be compatible with the 57. The reamer pilot will probably not fit.

thanks G -- but i was more concerned about the chamber

Jeffe I have no clue on the bore. Either the 280 or 7x64 will clean up most of the 7x57 chamber. The issue you can have is the neck area of the 7x57 neck is something like .3207 and the 280 is .315. You can end up with a little ridge that may need to be dealt with

Jeffe -

Depends on whether you already have the reamer you want to use, or whether you have yet to buy one.

If you are going to have to buy a new reamer anyway, you can always order one with neck and lead dimensions to clean up whatever the standard 7x57 dimensions are. I'd suggest talking with Dave Manson who posts here. He knows exactly what you are facing and can doubtless help you out.

The first thing I'd do, if it was me, is make a cerrosafe cast of the 7x57 so I could measure what its dimensions really are now, rather than relying on theoretical specs which it may or may not meet as is.

If you already have the reamer, then I'd probably just do what Vapodog did.

Hope you feel better soon,

AC

quote:

You can end up with a little ridge that may need to be dealt with

I've used a wrap of 150 grit emery on a stick to deal with this.....maybe not the right thing to do....but you did decide on using a milsurp barrel! It works for me!

BTW....I fired some Barnes TTSX 120 grain (.284 bullets) in my VZ-24 7 X 57 yesterday with 44 grains Varget and achieved nearly 3,000 FPS....

If the bore is significantly wrong....those Barnes bullets didn't know it!...and yes.....I did work up and no....I didn't slug the barrel.

One thing to bear in mind is the twist rate. Most of the 98 military models have a fast 1:8.5 or so twist. Could create pressure issues with top .280 loads, and not allow you to reach velocities you desire. 7x57 AI or .284 Win would let you take full advantage of the magazine length and get you real close.

okay .. what i am hearing is "probably" .. which is fine .. i already have one 7x64, and the fast twist works for that one ...

Bobster, you are 100 CORRECT that fast twist will result in higher pressure.. btdt, paid the money for the barrels myself ...

I want mild shooting 7x64 .. because i actually have more 7x64 brass on hand than 7x57!

I have two Brno 22H rifles, rechambered from 7x57 to .280 Rem. and I would have had it done in 7x64B to keep them "Euro", BUT, the case diameter just forward of the annular grove is smaller than the 7x57, especially in those old Chech rifles. Sooooo, it seems that IF one already has a 7x57 or a few, the best choice is to re-chamber to .280 R. and quite a few 22H rifles I have seen have had this done.

I keep my Brno 21H 7x57s as produced as there is no value in that short tube being re-chambered, but, the 23.6" 22H makes just a fine .280Rem. and my favourite, a "roundbolt" gives me over 100 fps more with 160NPs that it would as a 7x57.

It is at Martini's getting a Wisner 3-pos., bolt jeweling, Recknagel trigger and Bansner stock. I had to totally glassbed the original stock as it was so cracked, but, the metal and bore are excellent and it shoots tiny groups and carries so nicely.

So, I would opine, go .280Rem., along with the .338WM, the finest cartridge ever developed in the USA!

IIRC, Ken Waters did this very thing many years ago with a military Mauser of some description. He ended up with accuracy issues and blamed them on the little ridge in the neck area.
Regards, Joe