I recently obtained a 4yr old CZ550 American in 9.3x62. I've worked up several loads, one of the best using H4895 and the Nosler 286 Partition @ 2400 fps.

Several days ago I was zeroing the rifle at it's 208 yd MPBR zero. The temp was about 59 degrees when I started and about 70 deg when I quit. I had several 3-shot groups working towards the zero. Finally got dead on at 208 yd. The next few groups went a solid 4" high.

Any ideas what went wrong? I've heard H4895 is temp stabil but can boost a bit at 70 deg. My barrel is has full contact. Should it be free floated?

If it were mine, first thing I would do with a new or used wooden stocked gun is make sure the gun isn't bound by releasing the tension on the front guard screw and watching what the barrel and action does. If it moves I would correct that, then I would float the barrel, recrown the muzzle and square away the trigger before the start of any load developement.

Westpac,

Not sure what you mean by "bound by releasing the tension". I can imagine it means loosen only the front guard screw and if I see the barrel raise up out of the channel, their's problems.

PM sent.

quote:

Originally posted by GSSP:
Westpac,

Not sure what you mean by "bound by releasing the tension". I can imagine it means loosen only the front guard screw and if I see the barrel raise up out of the channel, their's problems.

PM sent.

That's what I meant. It is my belief, that before you can really see what a rifle will do, you need to first remove all the obvious and potential accuracy destroying problems without replacing components, unless it is obvious that they too are out of whack. You need to start at a neutral point and go from there.