375 H&H COL for a CZ550...help?

[KDM]

Relaoding question for ya...trying to maximize accuracy in my 375 CZ550.  The first load I'm working up is a Barnes 235 grain TSX flat base with RL-15.  The goal is to adjust bullet seating depths to determine an accuracy sweet spot, and I'd like your input / experience.

I tried using an OAL gauge, in conjunction with smoking the bullet, to see where I'm touching the lands.  I must be a 'tard because I can't for the life of me see rifling marks.  So, I measured the extreme length of a cartridge touching the lands out at around 3.8".  I thought if I were to start at the standard 3.600" COL, I would make increases of .050" and see which length would provide the best accuracy.  Longest cartridge would be 3.750".

Does this sound like an acceptable plan?  Have any of you tried something like this?  What were your results?

[mauser98us]

I insert a bullet where the case just holds it, then cycle the action closed till the bullet jams into the lands.  then I seat the bullet ten thousands deeper and call it good. Obviously,if it doe not fit into the magazine,you must seat deeper. Remeber there is a little more recoil to the 375,you dont want the bullet to move under recoil and bind in the magazine

[KDM]

Thanks, mauser.  Man, that's gonna be a long cartridge!  Using a Hornady COL gauge I get 3.815" touching the lands...going off Barnes' recommended .050" off-the-lands depth, that means 3.765" is my max possible COL. 

Thanks for the input.

[gwindrider1]

KDM,

If your 550 Magnum is throated anything like mine in .458, you'll need to seat your bullets out as far as the magazine will allow.  I'm using the Barnes 450 grn. TSX and am able to crimp in the second groove on the bullet.  I'm still not within .0050 from the lands.

Hey, it just gives you more room for powder.  Not a bad thing!