@Formidilosus when you are conducting tests like this how do you sort out possible variables like different conditions day to day,
Different environmental conditions do not effect 100 yard zeroes to any measurable degree. A 100 yard zero is a 100 yard zero from Death Valley to Mount Everest. So that’s eliminated.
cold rifle barrel verses warm barrel and so on?
No properly machined/made barrel or rifle has a shift in mean point of impact (MPI) from cold to hot. Rifles built and assembled properly have a true cone- that is a cone (group) where “x” precent probability of all rounds will fall within.
By and large a 30 shot group will show the extreme spread (ES) of where 95% of rounds will fall within- say in the case of the current lot of ammunition that the eval rifle is using, the 30 shot ES was just over 1.4 MOA. That means +/- 95% of all rounds from that combo will be inside a 1.5 inch target. Knowing this, if the rifle system is truly zeroed with the MPI and mean point of aim (MPA) are centered, then any if a “group” whether 3 shots or 20 shots is outside a 1.5 inch dot at 100 yards- the system has had a zero shift.
The key to doing this is knowing the true cone- which requires a 20-50 shot group size. The less number of shots, the more potential variability, the more shots the less variability.
20 shots is sufficient to see a zero shift of .2 mil or .5 MOA (+/-) or so at 100 yards, 30 shots will show a shift of .1 mil or .25 MOA.
Then, ince the true cone is known, you need a true zero- that is center of point of impact (POI) is the same as center of point of aim (POA)= center of all rounds fired is centered on the aim point. DO NOT EXCLUDE SHOTS YOU DONT LIKE. All shots count.
Example from the eval rifle and ammo:
Rifle and ammo is 1.4 MOA, and the rifle is zeroed correctly. From then on, if a round misses the 1.5 inch dot at 100 yards, then a full group of 10 shots needs to take place to see the center of the POI. If that center is has moved .2 mils or .5 MOA or more, it is very apparent.
There could be a lot of variables here.
There really is not. Shooting is simple. People try to make this “test” seem complicated out of ignorance or because they don’t want the truth to be know- usually it’s both.
1). The rifle’s action is permanently glued into the chassis.
2). The pic rail is permanently glued onto the action.
The shooter, rings, and scope are the only “variables” that could change.
First, in shooter is not the variable that people try to make it out. Over extremely large sample sizes, anyone that has a base level of shooting skill adds only about .5 MOA of group size from rested positions- not zero shift errors. I.E., their group size might be .5 MOA larger than a machine, but the center of their zero from the same position doesn’t change materially when firing statistically relevant sample sizes.
For what it’s worth, my measured average is sub .2 MOA for 100 shot groups compared to a Wiseman return to battery system. Most solid shooters are about .2 to .3 MOA of a Wiseman.
Second, the rings. The rings get removed as variable once multiple scopes are used in those rings and show no point of impact shift from impacts ever, and no POI shift when used for long periods of time (round counts). The reason that a 308win is used for the eval rifle primarily is because of barrel stability- it has an extremely long plateau or flat spot where zero/MV, etc does not change. That is thousands of rounds. 308win also provides some recoil to the scope that a 223 rem does not.
That leaves “scopes” as the last variable. If scope “A” does holds zero for dozens of drops, then without removing rings, scope “B” is placed in them and torqued down correctly, and scope “B” shows consistent loss of zero from the same drops that scope “A” did not- scope “B” is losing zero. That is further confirmed when you take scope “B” out of the rings, replace scope “A” back in them torque correctly, and scope “A” still does not lose zero. The logically tells you scope “B” is the problem.
The key here if you read all the eval threads, is that there is no condition- that is ring type, torque, or rifle that scope “B” holds zero. It always shifts on every gun. However, if scope “A” holds zero always on a single gun, the scope is fine.
No matter how many times you drop a Nighforce Milspec, it holds zero. No matter how it is mounted, this Leupold loses zero.
The only variable is the scope. This isn’t a one off. This is provable with 30 minutes on a range, on demand.
I ask because I lack the experience that you and others do. I am trying to figure out what may be in consistency in my reloads, personal abilities, and my equipment.
I’ve wrote that if someone has a zero shift, the first step is ensure that their rifle is holding zero. The only way to do that is to check with KNOWN scopes. If someone drops their rifle with 2x Nighforce NXS’s and both have a zero shift- they have a rifle system shift. Somewhere in the action to stock, or mounting system is moving. Everything can fail, but two Nightforce NXS scopes losing zero back to back isn’t happening. Once you know that the rifle is holding zero, then you can determine if other scopes are holding zero.
For nearly all people, both their rifle and scopes are losing zero.
