Hi grauhanen, thanks for the reply.......not that it matters, this is on a CZ 457 not a Tikka T1X
After what I spent on this barrel I want to milk out as much accuracy as I can muster so trying to line up all I can to achieve the best results.
Certainly not the sharpest knife in the drawer so doing lots of reading and hopefully will learn lots in the process!
I was quite surprised the barrel tenon length on the Lothar Walther is identical to the factory CZ barrel (1.189") - so both are close to the maximum headspace as receiver to bolt face = 1.239"
Just going by what I have read, all things being equal, a number closer to the minimum headspace should produce a more accurate rifle??
From what I have read, if you take in consideration the rim thickness, .006" between bolt face and rim base to be ideal. If I use only Eley ammo (average rim thickness of .035"), I should be able to get away with a headspace of .041ish.
Yes, the barrel tenon is bottomed out to the receiver as there are no shims presently used which is why I assume I would have to set back the barrel shoulder to achieve the desired result?
Anxious to absorb all the information you would like to share.......cheers!
My apologies about misidenfying the rifle. For some reason I had the Tikka in mind.
If it means anything, Bill Calfee says in his book and elsewhere that headspace has nothing to do with rimfire accuracy. Speaking about .22LR (which has the same headspace as 17 mach2), Calfee said, "
If your headspace is safe, and if you have killer ignition with it, the headsapce itself, no matter what it is, has absolutely nothing to do with rimfire accuracy...
I recommend setting HS at .043", with the ammo we have available today.....same as I've done for years now...." h ttp://www.wwaccuracy.com/showthread.php?t=4344
I don't know how to specifically evaluate ignition, but in the end a safe headspace is desirable, and as close to .043" is most desirable.
Lilja drop-in barrels for CZ rifles have a longer tenon that measures 1.200". These barrels are supplied with shims to achieve the headspace the shooter wants by using the correct shims on the barrel tenon.
Since the Lothar Walther drop-in barrel has a shorter tenon, shimming it won't achieve the desired results. If headspace is excessive as the LW barrel is, it would appear that setting back the barrel shoulder as you describe would be one way to achieve the headspace sought. The other way would be shimming the bolt.
(As a note for the general reader, when measuring tenon and receiver to bolt face lengths, a depth micrometer will give more reliable results than a typical digital caliper. The depth micrometer is better designed for this purpose.)
For some information on how to shim the CZ 457 bolt, there's a thread on RFC with some details and photos (which for convenience are reproduced below). See post #39 here
h ttps://www.rimfirecentral.com/forums/showthread.php?t=1163215&page=3
Regarding rim thickness, if 17 M2 ammo is anything like .22LR, there will be variation from round to round.
Regarding accuracy, like 17hmr ammo, there is no such thing as 17 M2 match ammo and as a result there can be considerable inconsistency in a box of ammo. This may impact accuracy expectations.

