I'm grouping about 1.5 - 2" @ 100 yds. with a TC Omega. Shooting 100gr of BH209 and Win W209 primers. I'm shooting the 250gr SuperGlide, and the 240gr PR Dead Centers shoot about the same. Would stepping up my bullet weight to around 300gr potentially improve accuracy?
For whatever it's worth, the most accurate load in my T/C ProHUnter is 120gr (V) of Blackhorn 209 under a 250gr T/C ShockWave with the standard sabot. It has shot 2" groups at 200 yds and shot a 3" group at 300 yds, but only did that once.
I shot a small buck @ 100yds the other day. Slug went diagonally through the shoulders. Deer was smacked to the ground and never moved.
The 250 gr will be slightly more accurate then the 300gr. I recommend sticking with a 250 gr bullet. I also recommend sticking with W209. The only thing I would change is how much powder you are using. Since you are shooting 100 grains now, I recommend shooting a group with 105gr or 110gr of BH209, see what kind of groups you get and shoot another group with 115gr and 120gr of BH209. After doing this, does your groups grow or shrink? I also recommend using 250gr Barnes Spitfire TMZ's. VERY accurate and hard hitting.
In my omega, iam using....
110gr of BH209
250gr Barnes Spitfire TMZ
Nikon Omega BDC Scope
Bullet weight in and of itself has no relationship to accuracy. Question is, do you NEED superglides? If the regular sabots load ok then you will get WORSE accuracy with superglides -- a tight sabot is good as long as you can get it down.
Some guns seem to like a certain velocity range. For example, max accuracy with the 200 Shockwave in my Omega is 110gr (2050 fps). Since the gun is rated to 135gr loose 777 I'm not using all the power I could, but accuracy is #1. So this year I moved up to the 325gr FTX and have also tried the 300gr Shockwave, both of which go 1950fps with 135gr loose 777. So I get near the same velocity as a bullet only 2/3 as heavy and use the capacity of the gun's power.
The Dead Centers are another story. Somewhere between 1800 and 2000 fps your accuracy will go to crap because the soft lead bullets can't handle more than that before deforming (their BCs are WAY inflated anyways).
There are a number of other reasons your groups won't shrink. The barrel could need floating, the action bedding, etc.
100-110gr of Blackhorn 209, CCI209M primer, with a 260 or 300gr Harvester Scorpion PT Gold bullet with crushed rib sabots will tighten things up. Most .451 .452 250-300gr bullets in a crushed rib sabot load with just the right resistance and shoot great in the TC's.