TLDR: - When the variability of your group pattern is much larger than the change in point of impact of the group per step, you have some fundamental problems to solve before you will make progress with load tuning.
My opinion is that a GAP Crusader should do much better so some fundamentals are in order before you attempt more load development.
There are some talking points we can make that are just food for thought.
There are risks in likelihood and consequence for each one.
The Arrow... (which includes the bow...)
You named a well known manufacturer who we will give the benefit of the doubt for the time being, although if the barrel is aftermarket we will circle back to that theory.
Let us assume the gun/barrel/chamber are assembled correctly and not the cause for the moment.
That still leaves us with anything we did to it, i.e., scopes, mods, loose fasteners, muzzle devices, etc., so give the whole works a thorough examination and then scope the bore.
If this type of debugging isn't something you are versed in, it usually isn't too far to find some help.
Aside from this hardware debugging discussion, has this gun ever shot tight with anything else? If the answer is yes, we are not wasting time debugging but if the answer is no, then the list of risks goes up. Let us park the risk of the barrel for a moment.
Is this rig new?
Was there age or lots of cycles on the firing pin?
Was the barrel mounting system changed or the action/bolt blue printed?
(I have to ask because I am not aware of this being offered in 6.5 CM, but you will tell us if otherwise.)
Sometimes a barrel hates a bullet (or a powder with that bullet) and the best it will do is mediocre. We are discussing a rig that is north of $5k, so we will assume the goal is 3 shots <0.5 MOA and generally well inside 1 MOA for slow fire strings, unless you modified the barrel design or it wasn't executed well. If that barrel was from GA Precision, you should seek their advice and get a baseline of the ammo they recommend. Their guarantee is based on match ammo, not hunting ammo. So we will want to find out what they recommend.
When something is this far out of whack, there is value in trying anything else at hand to see what this rig can do. As a beginner or beginning reloader, testing against some factory match ammo baseline is a tool you can use to debug a bad day.
The more similar this factory baseline ammo is to what you will be loading the better. For example, if your particular hunting bullet comes in factory ammo from a reputable source, give that a try. This will give you a reference baseline goal as a beginning reloader.
If that hunting bullet factory ammo still looks bad, then try to use exactly what the gun maker uses when they test if possible.
What did they use when they came up with the GAP Crusader in 6.5 CM? I am retired now so I don't keep up, but the Crusader used to be offered in 308 WIN and came with a < 3/8 MOA precision guarantee. (If the 6.5 CM barrel is aftermarket and unproven, we may have to question any assumptions we made earlier.)
The value of the testing with factory ammo to get a baseline, is it cuts the troubleshooting list in half. We would know that the gun is good and the shooter is good, but the hand loading needs work. If that hunting factory ammo didn't do as well as the GAP recommended match ammo, then the challenge will be down a different path, but at least you will know you are not chasing down that path for nothing.
The Indian....
The next big possibilities are "The Indian" steering the gun.
Only you know if your skills and background are at the point of shooting well enough to make that many shots without throwing a single one.
All of us will have a bad day now and then, but that discussion comes after many years of knowing the difference between a bad day and what we can normally do.
What is your normal capability with a known similar weight gun and caliber?
What is your normal capability with any other target rifle?
Have you ever been able to shoot 20 to 50 shots into < 1/2 MOA with any other combination?
To end this wall of text on a more upbeat note, don't sweat it if you are still learning the ropes of shooting or load development. You spent good money on a well regarded rig and as long as the barrel wasn't a lemon, you will get there. YMMV
