Dear RHD45
I've read a lot of your posts and appreciated every one.
I think that the 6.5x53 is also called the 6.5x54, these
are different than the 6.5x55. To complicate matters, there
are rimmed and rimless versions of these cartridges.
I bought a mauser rifle awhile back, where no one knew what it
was chambered for. I measured the barrel groove diameter
and figured that it was close to that of a 257 roberts.
So I tried chambering a 7x57 mauser cartridge with the neck cut
off* and it fit nicely into the chamber. It did not slide
too far in, nor did it wobble. The bolt closed ok. To test
if it was a 257 ackley improved, I coated the front of the chamber with inletting black and ran an empty cartridge from the
magazine into the chamber. The thinking was that if the extractor held the cartridge against the bolt face, the only way the shoulder of the cartridge would touch the inletting black is if it were the correct cartridge.
my suggestions are to do this. Remove the firing pin and try
to chamber the cartridges. If they don't chamber or if they do chamber but the bolt doesn't close (don't force things), then they aren't for the rifle. If they do chamber and do not slide
too far in, nor do they wobble in the chamber and the bolt does close, then try my trick above with the inletting black. If that works, check headspacing with shims. Check also that the bullets test against the muzzle. Everything I written up to the last point would allow one to conclude a 270 would work in a 30-06 chamber.
please ask if these instructions are not clear
* the 257 roberts is a 7x57 necked down
