sw28 - I am definitely going with the Boss on this one. Dust off that old 22 and get yourself a brick of new ammo and get back to basics.
By laying on the ground before shooting you, in effect, benched or rested your revolver. This helps you to determine the accuracy of the gun and where it is shooting. Before I start practicing with any of my hunting loads I bench my guns to make certain the gun is still shooting straight and I didn't knock the rear sight out of alignment (which I have done a couple of times necessitating a return to the range).
Cheap loads may neither give you the accuracy or consistency of quality ammo/reloads or your own handloads. I prefer to use my hunting handloads when I shoot and practice with my S&W M28 and if I go to using other loads I will leave the sights as they are for the hunting loads and use Kentucky windage until I am ready to go back to my hunting loads. Switching loads often means switching sight settings which can lead to trouble hittin' what you are shooting at in the field.
One bit of advice please - be very careful with your 9 yr old and full house 357s, or any handgun for that matter. Young children get injured on gun ranges all the time especially when they are doing what they have no business doing and 9 y/o children have no business shooting powerful handguns. Shooting powerful revolvers at age 9 is not some 'Right of Passage' - and please note how I spelled that, and neither is it a 'rite of passage' for a 9 y/o'. 'Ripping off' 158 gn 357s by a 9 y/o kid, who tells you that you're too old to shoot the gun, would get you all thrown off my ranges, and there is absolutely no way I would ever allow a 9 y/o to put his hands on my 1911, period. Any 9 y/o who says full house 357s don't kick at all is either the size of a professional linebacker, or probably about ready to lose control of the handgun. They have no business handling handguns of that power level - there was a slightly younger child killed by the recoil of a handgun when it kicked back and hit him in the head. Those children I have seen receive 'S&W Hammer Bites' to the forehead don't usually go about wearing those scars as badges of honor. If he wants to shoot, let him develop his skills with that old 22 while you supervise him into absolute boredom. When he can get to the point where he can hit as accurately at 75 yds with that 22 as you want to be with the 357 then you can let him hunt with that 22 while you remain in full supervision, which means full control of him, the handgun and the situation.
It is simply far to easy for younger children to have, or cause accidents while shooting, especially if they are under less control and supervision than they should be. Firearms instructors who teach adults how to properly shoot a handgun often start with mid-level revolvers and one round at a time. Those instructors also stand or sit right next to the newer shooter so as to maintain full control over that handgun at all times. 'Ripping of 357s' does not make it sound as though you are in full control of that handgun......, or your 9 y/o son.
500 - naw! Mikey.