392 point of impact changes

[joe444]

I am getting my 392 close to where I want it for power, and it is pretty accurate on the different power levels, but the point of impact changes with the number of pumps used. I would expect it to go up and down with the number of pumps, but it goes right and left also:

5 pumps might be on at 10 yards, but 6 pumps would be left and higher, and 8 might be low and to the right

is this a crown problem?

the groups at the different pumps are good, but they wander all over the place

[BenjiHunter]

Have you removed the paint inside the barrel at muzzle?
If not, use paint stripper and a Qtip.
Be careful so you don't remove paint outside the barrel.

[MikeSSS]

Different POI with different velocities is not a surprise.  Also, different POI side to side as well as vertically with distance changes can happen...if the pellets follow a spiral during flight.

I tend to shoot pumpers with a fixed number of pumps for almost all shots.

[joe444]

this 392 is a 2003 from the serial number, and I bought it used to practice the mods I want to do to my 2 new ones. I have not cleaned the muzzle with paint stripper yet.

so far I opened up the valve a bit, cut grooves in the receiver for a scope, took the sights off, opened the transfer ports, shimmed the pump cup, and installed lighter springs.

next up is the muzzle cleaning and a recrown to see if that fixes the wandering groups

then make a new adjustable pump cup holder to set the piston head space, then make a new linkage and pump arm and cut the stock like mac1 does and front cap and pivots and such and a few other mods

I was hoping that maybe someone else experienced the wandering groups from side to side and found what caused it.

my 2289's don't do that, or not so much that I have noticed. they will go up and down according to the number of pumps, and the size of the groups will change according to the number of pumps also.

[brzryder]

Clean out the muzzle paint and recrown it then do your shooting tests the paint makes a big difference and the recrown will never hurt

[454ho]

What pellets?

I had a similar 'wondering POI' with Crosman 14gr wadcutters at different #'s of pumps. Seems like they liked 3 or 4 pumps the best. Any more than that was pointless for accuracy past 10 yards. Crosman HP pellets are pretty accurate to 25 yards at any # of pumps... that is the longest distace I have shot so far. I also have some JSB Heavy and Extra Heavy to try. Supposedly the 18+ grain pellets are even more accurate in pumpers.