I have loaded 50 grain Ballistic Tips, to 68grain Hornady Match BTHP for a friend who shoots a SIG with a 16" barrel. The best it groups at 100yds is just inside 2 inches. Should we be able to do better with loads or is this an operator issue?
the rest should support the stock only and ideally mimic where the forehand holds the rifle.
Never place the barrel on the rest as the resonance and kick will spray shots all over the place.
The other thing you could check is that the stock is secured properly, if its too loose this won't help. Don't over-tighten, just pinch it tight.
Id try 2 brands of factory ammo, just buy 2 different brands and they should both group about 1" at max at 100 yards. If this fails after doing the above suggestions then id take it to a good gunsmith and relay the problem to him- it could be a burnt out barrel or damaged crown
Shortmag--Whats your twist?. If 1 in 9 you need to get to a heavier bullet. What powder you using and what is your COL,Primer,and better yet,,what bullet brand you using?. I agree with other posts here. At 100 yards you should almost be making one hole in paper for sure.